Marshall 2203 Keeps Blowing Expensive 6550 Tubes!

[@jackiefarmer4892]

Hi Brad, Alan Here. I have a repair business in New Zealand (Anvil Amplifiers). CEdist have done the same to me with a quad of 6550EH. Because the Tubes were in my stock for more than 90 days until used and I only then discovered that one of the tubes had an open circuit heater they told me I could not get a replacement. Am I supposed to test all tubes on delivery? BTW I now buy most of my tubes bulk from JJ direct or other brands from UK distributors. Just bought another 3000 Euro worth.

[@TheGuitologist]

It’s bullshit, ain’t it!

[@neutrodyne]

I'm in the US and have had the same proble with CE and their 90 day policy. I have tried to tell then as a repair center that I stock up on tubes and then sell them as needed. Some times the tubes set on the self more than 90 days before they are needed. CE told me 90 days was thier policy. I told them it was a unreasonable policy for a dealer/ repair center.

[@highpath4776]

UK has just done a free trade deal with NZ, so that should make you happy in the future - be good !

[@Pentode3000]

If there is high frequency oscillation in the amp going on as seen in the flashback and while you were testing it on the bench there is something wrong! If the customer doesn't use the FX-Loop disconnect it and put the amp back to original. If he want to keep it test it as well and ask how he is using it. Depending on what is connected there it also could lead to oscillation. High frequency oscillation can kill the amp without you even noticing it. Replace those sockets! And CHECK the coupling capacitors!!! If they are leaky the Bias will run away. Replace them with good 630V types as 400 are not enough! Yeah modern foil caps blablabla, i've had exactly that in a Laney. The cap was damaged internally and when it got hot it leaked and the tubes blew. Also by changing the grid resistors you have now changed the bass response of the amp. If the customer doesn't notice it okay otherwise enlarge the coupling caps. Keep an eye on crossover distortion when running it with less bias. Finally get rid of those 6550 and put EL34s in. Those are what the amp was made for. You are putting a V8 in a Mini and wonder why the brakes are failing.

[@trespassband]

Ya know, I have always pretty much considered myself a Guitologist fan and have always enjoyed the videos but this one disappointed me. Why would you expect a company to replace something that far beyond their return policy. There has to be a limit. Just because there has been a pandemic and the customer hasn't played any shows doesn't mean he hasn't used the amp. I haven't played any shows either but I still crank up at home. I could understand if it was a only couple months over the return period but how long was this... well over a year? The part that really disappointed me was that after you belittle and berate this employ on the phone and claim that the amp is not at fault, you proceed to test the amp again and discover that the amp probably was at fault. To me, it was you that missed the heat issue on the previous repair and had already been comped one tube. It seems that this company had already gone above and beyond their responsibility to you as a customer and I applaud them for standing up to you when you tried to bully them with threats of using your subscriber base against them. Just my opinion...

[@petemoore8923]

Well said sir!

[@j_freed]

Yes, given the global crisis (which nobody in the situation caused) Guitologist is placing the entire locus of control for the warranty runout problem entirely on the tube reseller. This would in principle also make the company liable for countless thousands of other products that have all been sold since December of 2019, regardless how the items were used or handled or stored for all that time. I think one assessment is to say: as with other crises like terrible wars, everyone owns some material loss from the pandemic, and we can’t all shift it onto someone else. It really sucks but in the balance we still have a really great life here to be grateful for. In fact, Guitologist might have done better in the long run sticking by this company… I don’t know. They did try to offer him the item at cost before he shut them down with the ‘long term customer’ refrain. That would be effectively one tube at a full loss, and one tube for zero gain, all assuming he’s 100% correct and above board. You can’t buy that good faith and respect. I guess businesses sometimes have to let customers go.

[@verifiedhandle9103]

@@j_freed lol except for the rich who have all gained wealth

[@benlogan430]

Even in amp and guitar land the talk of “sheep and goats” comes out. This is amp and guitar land. Rock and Roll.

[@NewHopeAudio]

100% agree ...this is disgusting.

[@joosboer1030]

To be fair, it’s not that clear the tubes were entirely at fault, especially since the grid resistors were out of spec, which you replaced. As such, you should pass the cost on to the client and explain the tube failed and too much time has passed to qualify for a warranty claim. I can see their perspective as well, where do they draw the line?

[@stephc4427]

Wait a minute. The customer is responsible for his own equipment and the costs therein. Brad you are totally wrong to say that you have to eat the cost of the tube. That's you customer's responsilbity just as it would be if he had purchased a quad on his own and installed them. You need to get your business acumen in order. The supplier already did what they agreed to with the initial replacement. Plus, you have NOT proven that the amp itself is blowing up tubes nor did you explain that the bad tube was in the same socket as the other that faile! Cmon, get real,

[@tombryan1]

@@stephc4427 It's not the customer's fault. The expert who repairs the amp has possession and agreed to repair it. Good business practice means taking responsibility. You wont last long in business if everytime you misdiagnose you throw it back into the customer's lap.

[@Hahnsoulo]

@@tombryan1 That might be true in the world of guitar amps, but not in the world of cars. Plenty of mechanics will replace a part because 90% of the time that's the part that needs to be replaced when symptoms X, Y, and Z occur on a particular model of vehicle, and then when it turns out this particular case is one of the other 10% they have to replace something else to actually fix the problem, and the customer gets charged for the part and labor of both parts. Have you never heard of someone having to take their car back to the same shop 2 or 3 times before it actually gets fixed? It's pretty much standard practice to fleece customers whenever possible, and these shops don't go out of business.

[@erichkaanikin3555]

You also don’t vacuum the dust off. Isn’t that proper amp hygiene?

[@erichkaanikin3555]

Gosh, how can you possibly think you’re anything close to rational by claiming that a purchase with a 90 day warranty should still be honored three years out of warranty because the customer didn’t play, whether or not due to pandemic. That’s ridiculous! And certainly not relevant to the vendor’s warranty. Your reasoning is pathetic and an embarrassment to the customer. Sad🙈

[@haplozetetic9519]

The amp isn't built for that kind of power consumption. I think these tubes need to be biased to draw no more current at max volume than the original EL34s would. Anything higher would reduce the life of the output and power sections. Another thing I don't hear about much is octal socket contacts. I have encountered so many amps with socket problems that I check all the octal contacts of every amp with output tube issues. I use an old screw driver (with the tip rounded off) with a shaft that is only a hair's breadth smaller than a tube pin. Any contact that doesn't have a fairly firm grip is gently bent to make better contact. If the contacts are charred, the socket is replaced. Better safe than sorry.

[@highpath4776]

Good Analysis.

[@acexxxoasis]

Not gonna lie I'm not trying to stick anything metal into a tube pin socket, drained or not I would be shitting myself one way or another!

[@golgothaassassin5035]

Agreed!!! I've seen so many of those cheap china sockets fail, or cheap wire that breaks down with use, or thin conductive boards.

[@andrewpike2924]

Check the coupling cap from the previous stage feeding the grid. If leaky it will put a positive voltage on the grid. This will kill the tube.

[@woodhonky3890]

I bet it's got something to do with electricity.

[@swettyspaghtti]

XD

[@metalmig]

🤣

[@VashStarwind]

lol

[@rangerdoc1029]

Nailed it

[@docdeens4030]

It could also be thirsty. Pour some water in it.

[@TruthSurge]

31:20 are you going to cry, man? You bullied the poor customer rep and then threaten them but sometimes you DO have to eat some cost on a job for one reason or another. You can ASK, but you don't always get what you ask for. Buy another tube, add half of it to the cost of the repair and move on with your life.

[@TheGuitologist]

I moved on with my life by stopping buying from them.

[@TruthSurge]

@@TheGuitologist That's fine. If you were a 5 year customer and bought a lot from them and they wouldn't comp you one defective tube or two per year, then I get your point. It's business. They have to decide if it's worth ignoring their hard/fast 3 month warranty rule and lose $20 OR tell you sorry man, we got rules and lose hundreds of dollars in the coming months or years. Really been enjoying your vids though even though I don't do amp repair or mods. Just play guitar really. thx!

[@szaki95]

"Kan I speak to your manager?" - Karen The Guitologist :D

[@TheRustedShackleford]

"I'm a Yelp reviewer and I'm very important...." All joking aside, I see both sides, but its just a shitty situation all around. Let's just blame the Russians.

[@RaulHernandez-lg5nw]

Anyone who See's both sides of an issue, See's nothing at all !!!!!

[@TheRustedShackleford]

@@RaulHernandez-lg5nw ummm... thats a pretty moronic saying

[@taknmybeatings7036]

@@RaulHernandez-lg5nw that is tied for first place of the all time stupidest thing that I've ever heard! But I can see why you would say it.

[@taknmybeatings7036]

@@RaulHernandez-lg5nw I was just lying! I have no idea why you would say such a moronic thing! ...and on a public forum no less.

[@colincampbell4505]

Hi Brad, great video. Old school 6550 amps used to be driven regularly well beyond their rated max screen voltage. New production 6550s are not at all happy with high screen voltages. I have a stereo amp that drove 6550s at 550v on the screen. Used to work fine with nos 6550s. Eats new production 6550s like candy. I switched over to kt88s and tube failure ceased. KT88s are rated for over 600v on the screens. 6550s are only rated for 425. Check the screen voltage. What are the screen resistors? You may want to increase these. I use 1.5k - 2.5k for Amps like this. Adds a hit of compression but most often the effect is a desirable one. Or increase the dropping resistor for the screen supply to lower it. Although you would then probably need to decrease the droppers for the preamp supplies to bring them back up a bit. New production 6550s are just not as rugged as the old school ones. Their design maximums can't be exceeded like the NOS tubes.

[@TheGuitologist]

1K screens

[@colincampbell4505]

@@TheGuitologist Under the circumstances you encountered, I would bump those up. 2k probably won't hurt anything but might help the 6550's last longer

[@purgasound]

I used to bias those old Unicord distributed Marshalls using the 6550 specs and some of those amps kept coming back. Mostly with tube related issues until someone scolded me for it. The PT is what can't handle the extra current draw when using the 35W plate dissipation figure. You almost have to ignore the 6550 specs and bias the amp like it was using EL34's. The amp would have had a 5A mains fuse if it were designed to run 6550's like the Marshall Major, which does have a massive PT and OT to boot. I noticed the PT getting super hot in the amps I was biasing using 35W max dissipation. Once I started backing off, the amps stopped coming back to the shop and had less tube failures as well. Hopefully this helps. I think that cold biased sound of those tubes is why people get it in their head that 6550's and KT88's sound a certain way, when in reality they're just cold biased and have a lot more perceived headroom as a result. Tubes are getting expensive and a lot of times I've just converted those amps back to EL34's by changing those 82K or 150K grid leak resistors to 220K and adjusting the bias range resistor if needed. It was a strange reason Unicord got Marshall to make that change to U.S. imported amps in the first place and I think they gave it up around 1984 or so. As always, your mileage may vary. You know what you're doing. I'm just sharing my experience with you in case it helps your issue. I enjoy your channel so keep up the good work and have a great day.

[@TheGuitologist]

I appreciate you sharing the benefit of your experience. Thanks for the comment. Loads of others in the comments also concur with you. I have learned a valuable lesson on this one. I'm not immune to learning.

[@purgasound]

@@TheGuitologist Thanks for the kind response. For the record, I don't believe that biasing in anyway had anything to do with those tube failures, especially the one that had the toasted white getter flash. I agree you got sent some bad tubes. I had three modern "Mullard" EL34's from a matched quad arc internally and blow in an amp that had no other faults. That was probably the most astounding set of failures in new production tubes I've seen.

[@Shim267]

There were a lot of things you could have done before berating CE Distributions customer service like that; they run a good business and probably won't feel your absence at all. See Pentode3000's comment below - he covers most of what you should have checked. You know, I read the title of this and thought "NICE, Brad probably dealt with a really perplexing issue - I bet I'm going to learn a lot from this"... and then you started making phone calls... Please just post a 30 minute video of you fixing an amp next time and keep the yelp reviews off camera. It's unbecoming. "I'vE GoT 125k SubZ on Yew TewB!" - Yeah, and we're all going to watch you totally play yourself.

[@Blaculo]

I've been buying from CE Distribution for close to twenty years and they're the nicest, friendliest company I deal with on a regular basis. Your treatment of them with demands and foul language is uncalled for, especially when your own lack of knowledge and experience is to blame. Third time's the charm? Hope so for your customer.

[@TheGuitologist]

They should have taken care of the issue. The problem of people not being able to play due to covid was pretty unprecedented and they refused a return on a stupid technicality with a dealer who had been with them for years. Lack of experience? I have HUNDREDS of videos repairing amps. How many you got?

[@RozsaAmplificationLLC]

It's blowing 6550s because it wasn't designed to use 6550s and definitely not KT88s!! 2203s and the transformers were designed for EL34s. It was only when the quality of EL34s and high fallout, that Marshall had to scramble to get product continuing to flow out the door, so just dropped in 6550s. However the transformers can't handle the current draw, so if you use them, you have to bias them cold! Likewise, lay people that are naive and don't understand the engineering behind it, don't realize the output transformer is designed to match the vacuum tubes for ideal loads. However, the ideal load for 6550/KT88 is double what an EL34 is (5k v. 2.5k), so when using an 8 ohm cabinet, you can't or shouldn't have the impedance on 8 ohm, and it should be (i forget which way to go with it) 4 ohm or 16 ohm setting, but NOT 8 ohm!! Use the proper tubes (EL34s) and bias them correctly and you won't be stressing your amp and transformers and blowing shit up, it's THAT simple!!

[@theburkett67]

I like ya Brad, but throwing your channel around like that is an ugly look. We all have problems bro, but come on.

[@RobFeldkamp]

Agreed

[@paullee3660]

That was a real Karen move. 2 in a row from the same amp, 2 years later. They are a business, not a charity. That was a real tantrum and he needs to grow up.

[@j_freed]

KZbinrs primarily post videos to make money on views… Think about it.

[@TheEchelon]

@@j_freed This one seems genuine though. It's really not that deep.

[@BustedJunkStudio]

I had to watch this video again and I just realized that this amp has a circuit board and not a turret board. Marshall had a passel of trouble in the late 90's with conductive circuit boards used in the DSL and TSL models that would exhibit this type of failure as evidenced by slowly rising bias all the way positive many times. This is not saying that the board is the culprit but I had to have another look. I still don't know, it's a tricky diagnosis.

[@SIXSTRING63]

Yep, I have taken a Dremel and cut the PCB around the grid pin and ran a wire to the grid stopper resistor. This takes out the chance of a conductive PCB bleeding positive voltage from the screen pin next to it changing the bias voltage. I’ve done 12-15 TSL, and DSL amps with runaway bias. Seems his bias was changing as it warmed up. Marshall has been using these PCB’s since the late 70’s but whatever substrate they used in the 90’s was conductive with heat. You could take a heat gun with a meter clipped to the grid and see the resistance change as the heat increased on the PCB.

[@omarcusihuaman4261]

Hey, how can i contact you? Do you have an IG account?

[@BustedJunkStudio]

@@omarcusihuaman4261 Yeah, I do, it's bustedjunkstudio but I don't use it much.

[@glenwhatley4125]

If that is an added effects loop then the return jack is the best spot to inject your generator as you'd be passing all the preamps and tone stages and end up with a much more linear sine wave for analysis aft the output. There would be no guessing where any issues with linearity are coming from.

[@randypullman1155]

The guy on the phone is like "we will survive".

[@alejandrosilva7520]

Hi, maybe its all clear by now but your problem is high frequency oscillation because of the more than 50K return path to ground from the tube control grid. You can get away with more than 50K but with a very careful choosen maximun screen voltage and a super well designed output transformer and power supply. HF oscillation in 6550 occurs at high power usually and its very destructive for the internals of the tube. Marshalls are prone to it because of the long cabling in the power supply, in my opinion, and because OT are never well balanced, besides the obvious errors in the design. Thanks for the video.

[@Dennis-mq6or]

I thought that was what those grid stopper resistors were for. They usually eliminate any of those problems you described.

[@alejandrosilva7520]

@@Dennis-mq6or Indeed but the total value to ground, thats the stopper resistor plus the one that goes to the bias supply (ac ground), has a limit.

[@TrakThora]

You are right. I smell oscillation or alot of ripple.

[@jeremybender401]

I hope CE Distribution discovers the error of their ways. Good luck brother, we support you.

[@farfly7]

I never get tired of your intro graphics. They really take me back to the great days of cable. Keep up the good work

[@Geopholus]

This video is reminding me, of how long I have been working on tube amps, and also how long I have noticed subtle problems, that all contribute to catastrophic failures sometimes. Brad , I really appreciate Your channel and EXCELLENT videos. I will say I have commented several times on bias issues, and also parasitic high frequency oscillation. Although Marshalls have pretty good bias circuit components, I have noticed many times that they do not use the best pots. Often (35 years) I have ended up replacing them with fender style CTS pots, changing the typical reostat style circuit, to a voltage divider configuration, so the center sweeper goes to bias points through the splitting resistors, and eliminate the 2nd bias cap, as it causes the bias adjustment to take a minute to settle. A really solid bias setting,, that is a little cool makes for a long life with an amp used at high vol for hrs. Just as I was muttering to my self about hi freq or parasitic oscillation, I was much pleased, that You did show the earlier video excerpt of the parasitic osc problem showing up. If You use a 100 mhz or higher 'scope any parasitic oscillation problems will show up. That schmeary waveform is a lot of very short wavelengths of high frequency oscillation. If i ever get my amp You tube channel up, I will try to go through in detail, design issues that cause these problems and problems that show up as an amp gets older. Briefly an amp can become an oscillator very easily (at hi frequencies) if a couple of stray capacitances to ground in a series of gain stages show up in a negative feedback loop. You can't find THESE, misbehaving, until the tubes are in place and the amp is operating. Hi frequency oscillation can end up manifesting in a certain output tube, even when the tube is moved from one socket to the next, because each tube is slightly different, and at 50 Khz to perhaps several 100Khz, extremely small mechanical differences in the tubes can localize the power disipation of the oscillation in one tube , even though the overall instability of the circuit is to blame. It is very time consuming to go through amps to improve the stability. In this case it does seem that there was a bad run of Sovteks and especially problems with filaments overheating. I have had the same kinds of problems recently (over the past 10 years) with cathode filament shorts, with many different tube distributors, and manufacturers. I really like CE dist in general, but have had a couple of problems , with them and others more recently. It is actually very gratifying to realize that someone else shares my frustration, though it would be much better if we all could come up with a solution. Paul Carlson of Carlsons Lab YT does go into some issues of filament flash over during turn on,... that guy REALLY knows his theory ! A problem which can show up at a gig, that doesn't show up at Your repair facility are problems with Lamp dimmers making RFI, or outdoor concerts using power generators that supply squared off power waveforms. Brad I also really appreciate Your musicianship. Do You play out much? You are a great player!

[@MrZerohour1967]

After CE hung up the phone, I'm sure they will have agreed that the win for them is, that they no longer have to deal with you.

[@lewisokert1964]

I've also had problems with Sovteks. I recently returned a 5AR4 that arced over with very low hours on it. Also I've had problems with 6l6s. One low hour tube developed grid emission and the other one became noisy.

[@Dennis-mq6or]

After looking at your scope waveforms, I am concerned that one half of the push pull stage is going into clipping before the other one is...so you may have one tube doing all the work on 1/2 of the push pull output, or possibly an output transformer problem. The best thing to do to troubleshoot the problem is to look at the AC voltages across each one of those 4 cathode resistors to see if one or more are way different than the others. That could end up being something like a screen resistor that overheated and changed value, or it could be unequal outputs from your phase inverter stage that drives the grids of the output tubes. In any case, you will have to drive the amp into non-symmetrical clipping, (not square wave), and look at some waveforms to troubleshoot and repair.. And pray that it is not a shorted turn output transformer problem causing unequal loading of the power tubes. In any case...... It looks like you may get to produce at least one more episode regarding this amp repair on your KZbin channel..., and I will be looking forward to watching it...

[@SIXSTRING63]

Exactly! Just had that happen on an Orange Dual Terror. Easy test proved my theory. Unhooked all output transformer leads from amp, injected into the secondary a 5Vac swept sine wave from 30Hz-4Khz, used two channels of my scope with each lead on the two primary leads with ground on the center tap. Right away you could see one side was way uneven in amplitude from the other with notch distortion on the low amplitude side. Amp has shorted a tube, replaced tubes and would only push 6-7 watts maxed out when it is rated for 30. After checking all the obvious I tested the output transformer and bingo. What a time to find some of the right impedance, physical size for a lunch box amp that would put out 30 watts. Mojotone had a Trainwreck style output transformer that I made barely fin for $95. Either that or order from Orange and have it shipped from England. I bet it would have been $300 with shipping and duty tax……….. works great now. I bypassed that 2/4 tube switch too. Flicking a switch with 330v is just asking for trouble. Should never be switched only while off or in standby. Most players don’t know better and just do it anyway. Switch was jumping all around on resistance with meter in one position. I bet it arced internally. Has a half power switch for the output anyway, how many attenuation does one lunch box amp need. Hitting 32 watts with this new transformer. Personally with all the new tubes, caps and transformer you could have bought a used one. Terrible build quality, more Chinese junk. Just need to up the cathode bias resistance a bit. New transformer upped the B+ a bit. It was on the edge before with 120 ohm resistor for each pair of EL 84’s. RCA manual calls for 150 ohm minimum. I think I will try 180 ohm. Right now it is at 15 watts max dissipation. Need to get it under 12. Guy had a half dozen used tubes in amp soft case. Obviously been eating tubes. Orange didn’t design this amp well at all. Hopefully I took out some of the questionable design choices to make it more reliable.

[@sw6188]

Aside from who or what is at fault, here in New Zealand we have a very good piece of law called the Consumer Guarantees Act (CGA). It basically states that all goods and products must be fit for purpose, of acceptable quality and last for 'a reasonable period of time'. The CGA works over and above any warranty by the retailer or manufacturer. Example - you buy a TV with a 12 month warranty. 18 months or two years later it develops a fault. The retailer has to repair, replace or refund because an item like a TV would be expected to last at least 5 years. Whether they repair, replace or refund is up to the retailer, unless: • the problem can't be fixed • the problem is of "substantial character", e.g. the item is unsafe • the retailer takes too long to act on your complaint. Then you get to choose what action you want. The act only applies to things bought for personal use, it doesn't apply to goods purchased for commercial use, trade purposes or where you are making an income from their use. I don't know what laws you have in the US, but would be interested to know if there's anything like the CGA.

[@doctorwacky5680]

Hey Brad, I am an amateur radio operator. There has been issues for many years with power tubes for Amateur Radio power amplifiers, sometimes they were really good ones, and other times they would feel rather quickly. The quality with these things is all over the place

[@n8sdr473]

Absolutely same experience here as well TUBES these days are horrible, and most are just old stock and vacuum seal deteriorate over time

[@loosechangetrio1]

When I bias my JMP 2203 with 6550s I calculate as if the 6550 is a 25 watt tube(EL34). These amps are designed to run EL34s and it has to do with impedance of transformer why you do it this way. Just stuff I’ve seen in the net. Quote: You bias 6550's in that amp just like you would bias EL34's. The transformers were spec'd out around EL34 tubes so they aren't going to put out enough juice to run 6550's at their full potential. You also run the risk of running your PT too hard if they are biased too hot.

[@GranvilleGuitars]

This is exactly why I set idle current according to what the amplifier is asking for. NOT what the Tube Receiving Manual says they will produce. A 100 watt Marshall is asking for 25 watts each, so that's what I use for my calculations.

[@nikkisimpson1835]

Interesting, thanks for this information!

[@nikkisimpson1835]

@@GranvilleGuitars Thanks for sharing your knowledge Scooter, great tip!

[@scottdunn2178]

Ken Fischer always told me and I agree that some Marshalls actually sound better on 6550's. Yes, the Dagnall 100w output and power transformers are wound for EL34's, but over the years it hasn't seemed to have been a huge problem with replacing power transformers if running 6550's were really causing damage. Bias is completely subjective and finicky from amp to amp... some sound better at 15mA per tube, some at 35 or 40mA per tube. I remember the thrash metal guys in the 80's running 6550 powered JCM800/JMP 2203's liked a really high bias with hardly any current... thin, but super crunchy.

[@softsmoken]

Seems like something preceding the tubes is an issue, you gotta be missing something.. MrCarlsonslab channel might have some suggestions- dudes amazing with stuff like this.

[@simaojoseph]

I had a similar beef with a drum pad from Alesis. The pad broke within warranty, not because of miss use, the store sent it to the distributor, yes the distributor; the response from both was that they couldn’t replace the pad and it had to be repaired, and I would pay for the repair. I reluctantly agreed. The thing went to the distributor to be repaired and came back with a awful job with freackin cement glue showing. A BS repair job, that I simply could not accept, so I did not payed for it and they kept it. This is the best part; I contacted Alesis through their forum, explained them the situation and they promptly offered to send a new pad.

[@TheEchelon]

How's that similar? This was way out off warranty, they already replaced it once and it was probably the amp's fault...

[@simaojoseph]

@@TheEchelon look up "similar" in the dictionary.

[@kengevers8738]

Problem is Brad, if you bought 10,000 tubes, they would be talking to you. You only bought 4, so there isn't enough wiggle room to replace the tube. They replaced one, and you're asking for another. I side with your prospective, but I think you may have some success getting in touch with New Sensor.

[@SimonLarkin-CSRecording]

I think he's bought a lot more than 4. If you listen he has been a customer since 1994 and spent thousands of dollars.

[@chrissullivan40]

Brad buys lots of tubes

[@Dennis-mq6or]

The Tung-Sol 6550 is rated at 42 watts plate dissipation. Russian tubes often have less than optimum vacuum. As you increase bias to reduce plate current, you are also increasing the plate and screen voltages making it more likely to internally arc. To be safe, lower the plate and screen voltages, or at least the screen voltage because the screen cannot handle the higher voltage as well as the plates can. Burn-in is a very good idea because when the filaments heat up the cathode it activates a 'getter' material designed to remove any residual air and any new air due to tube pin seal leaks. Remember that the Marshall was designed back when most of the ac power outlet voltages across the US was only 107 volts. Now it's at least 10% higher. That means the plates and screens are operating at voltages that are 10% higher.. 400 V becomes 440 V in the HV supply. The best all round solution is to purchase a 12.6 volt CT filament transformer rated at the same current as your HV fuse. Hook the primary of that filament transformer across the HV fuse line, and then by choosing the phasing of the secondary windings of the added transformer and placing them in series with the primary leads of the Stock Marshall transformers, you can boost (raise) or buck (lower) the ac voltage going into the Primary windings of the Marshall stock transformers. 120 vac in - 12 vac bucking (out of phase ) voltage from the added transformer will give you the 108 volts the Marshall was designed to run at.. With the additional transformer you will be able to boost the line voltage by 5% or 10%, leave it stock, or REDUCE IT by 5% or 10%..... If you have weird intermittent tube problems in the power stage, buy yourself some 1 ohm 1/4 watt resistors and put them in the screen and cathode connections to EACH TUBE.. The idea being that they burn open before the tube destroys itself (or immediately after but hopefully that will not be the case. Next time a tube fails look for the exploded 1/4 watt parts and it will point you towards your cause. I would also replace that bias potentiometer on the off chance it was getting intermittent... You can also raise the voltage at the center tap of the filament transformer by using a voltage divider to raise the filaments to 50 or 100 volts above ground using a voltage divider off the high voltage power supply. . There's all kinds of things you can do to make those tubes work, but by far the simplest and easiest solution is with the addition of a buck/boost transformer... (it's like turning your variac down from 120 vac to 114 vac or 108 vac) You only need a high current transformer, (8 to 10 amps,) for that Marshall amp because it's high voltage transformers were fused at 8 amps, which sounds really high....... In typical guitar amps a 2 amp transformer is usually big enough.

[@ghramsey1681]

Great idea with using the transformer to "subtract" input voltage. I've built a portable version. I housed it in a box with a plug so I could use it on anything. I'm a tube amp enthusiast. Got into rolling my own for personal use. Small amps for hobby use. In 2013 I got an Ampeg J15 that is from 1960 at a yard sale from my across-the-drive neighbor (I'm in a condo) for $20. It's the 2x6V6 model not the rare type. It had 1/2 open OT, needed a cap job and proper 3-wire cord. Our line voltage here in Houston tops 121V and higher. I used the 12.6 V3A transformer to drop that 121v down to 108-109v. Works perfectly.

[@mikestillwagon5675]

My first real amp was a '74 Marshall MKII with 6550s. I can tell you from experience that if you're playing loud enough to get those tubes distorting it will part your hair and probably your scalp.

[@gearhead762]

@Orandy lol..youre an idiot that didnt read the description or get the point of that video you are linking into your comment.

[@gearhead762]

@Orandy read the damn video description.... you have no freakin clue what you are babbling about.

[@gearhead762]

@Orandy its a pro-woman video you bonehead. He just added some humor into it to take the edge off of the subject. He used the images you are bitching about to raise awareness of women being abused but he " just wants them to have fun" and be happy. You are just trying to brand it as something its not about.

[@CyberChrist]

@Orandy Thanks for that impromptu game of "spot the idiot".

[@CyberChrist]

@Orandy Don't make it too easy, though ;)

[@russellhltn1396]

I'm glad you changed those bias resistors. Note that the spec sheet at 59:23 shows the maximum grid resistance is supposed to be 0.050 Mohm. 68K is still too high, but 150K would be 3x the spec. It's unclear what happens if you exceed that spec. Some say you can have runaway bias - especially when the tube gets hot or gassy.

[@decadantdog4444]

That's what we have in politics right now, "runaway bias".

[@TeleCustom72]

Exactly this. I've had these amps back in the day where they still had 220k bias splitters with 6550s installed and the bias had run away and burnt up the valves (even with the bias supply adjusted to be biased correctly at idle). We get away with things in valve amps as they're very robust, but sometimes you get caught out. I too spotted the 50k max spec at grid 1 of 6550s. Some Marshalls in the mid 70s (with KT88s / 6550s) used 68k resistors for this application, so Marshall obviously were aware of this (despite still being over spec). I say that the bias will run away, but exceeding grid 1 spec might just (in some cases) cause the valve to become unstable and/or fail.

[@glenwhatley8034]

The way I understand it is the grid stopper resistors work with the tubes interelectrode capacitance to prevent oscillations in the tube. If the tubes were to go into oscillation for any reason they would inaudibly be drawing high current trying to amplify that ultrasonic frequency and all you might hear is a slight hissing. If the player were at a gig, he'd for sure never hear this or probably think it was just noise. I've see this type of oscillation in many older amps were it is merely lead dress causing the oscillation and sometimes a decoupling filter. The power tubes do their level best to honoraby amplify to the max whatever frequency it happens to be oscillation at.

[@ethanspaulding6067]

You are right Russell. Additionally, that spec is for a single tube. The leakage current from two tubes will generate 2x the voltage across it so 150k is 6x too high. As HTH AMPS says below, we do get away with a lot fo stuff in tube amps!

[@russellhltn1396]

@@glenwhatley8034 A valid issue, but I don't think that's what's happening here. A higher resistance value would lower the frequency of the resulting low-pass filter - reducing the problem, not creating one.

[@The0nionKnight]

What a dick move. There is NO reason why they should replace the tube for you. I just bought a set of matched gold lion KT88's from AES in support of them.

[@Cpt_Adama]

Those bias resisters were probably replaced by the importer when they changed the EL34's out for the 6550's

[@alwaysopen7970]

6550s were meant for the USA market as the EL34s didn't like the boat ride across the pond.

[@Cpt_Adama]

@@alwaysopen7970 During that time period they were having major quality control problems with the EL34's even before they came across the pond. After the importer started having to replace tubes all the time they decided to go with the 6550's which required a bias resister change. So they came over initially as EL34's and before they were sold they changed the bias resisters and the tubes.

[@pdog5731]

Reminds me of the time I once bought a brand new Ampeg VL-503. Had problems of the sound intermittently dropping out. Changed out cables, guitars; all made no difference so it had to be specifically the amp itself. At practice, I'd be playing then there it goes! The guys would look over and say "What happened!" Tue store owner I bought it from obviously got tired of seeing me haul it back in. That ended a casual friendship and I had bought quite a bit from him over the years. When it worked properly, that Ampeg WAS a beast, and even though I pushed it, I never abused it.

[@gavincurtis]

The gifts that keep on giving. Soul bonded together..... forever.

[@filonome]

Heck yea! What's better than a long form Guitologist amp repair mystery video on a lazy Saturday late afternoon? Thanks Brad!

[@OG_Wakanobi]

Viva Barnes on a Sunday evening?

[@briancounts8334]

Have not watched your videos for over a year because of your constant drama. I really find your videos INTERESTING. It looks like it's the same old thing.

[@doctortubes1]

Did you check BIAS stability ? Spring retainers are ground electrodes on top of the tube all around the anode, it can be dangerous. A current from plate can hit the glass over small spots , It depends on tube geometry. Usually no problems with el34, but other tubes may need different retainers..

[@oneox958]

My current tech refuses to use Sovtek tubes. Thinks they're junk OEM stuff that Marshall puts in their factory amps to save a buck. Sure enough, after a similar problem blowing one tube after another in my JTM, I went to a different tech and this guy switched to Tung Sols; it has been rock steady ever since.

[@gumbomudderx7503]

It’s probably kind of dishonest, but I’d wait a week and return the bad one on the order number for the new tube for a refund lol it would serve them right for screwing over a customer. What your saying is 100% correct. When I worked on the road as a guitar tech I kept a set of 6l6’s and 6550’s for the guitarist Marshall and the bassists Ampeg as spares. So if 3 months into a tour I had to change tubes and the new ones were bad, that’s now on me? Total BS man.

[@j_freed]

Just curious. Wouldn’t you break in a set of spare tubes so you know exactly the performance and reliability rather than trust brand new ones not to fail on the gig? I hear of players and studio amp techs doing this partly from a sonic perspective. Always keep on hand a newish set that is working and sounding just right.

[@gumbomudderx7503]

@@j_freed I’ve heard of people doing that too, but no, I personally never did. The guitarist I teched for used a Marshall 9200 dual monoblock, which is basically two separate 100w amplifiers, so if one went down I could switch from one half to the other until I could fix the main side he always used. That amp never had any kind of problems or failures. The bassist used an Ampeg SVT II Pro, and also had a mesa boogie (I don’t remember the model) as a backup. The SVT is the only amp that ever suffered a power tube failure on me while on the road. He also ran a DI box straight to the FOH board, and that’s mainly what the audience was always hearing. He ran a Proco Rat pedal to the amp for distorted parts and the sound man would blend the two, amp/DI, in the PA mix. Just the amp is what was heard on stage and in the monitors of coarse. The amp went south a little ways into the last song of their set, and with him DI to the PA I never even swapped to the Mesa. They were filming a music video for that song too, and his amp rack was in the back line, so I didn’t think it was a good idea to rush on stage and start repatching cords 😂 The next day they had more film shooting to do so it was no problem to pull the amp and service it. The bass player got on the phone with his Ampeg rep and he sent us another replacement set of tubes since I just replaced those. I swapped tubes, let it warm up for about 30 minutes and that was it. I never even had to readjust the bias if I remember correctly, the LED’s showed it was fine.

[@framusburns-hagstromiii808]

Yeah...dunno if I would have tried to throw the # of subscribers out to try and influence the outcome. I agree with the fellow who pointed out that modern 6550 are not as robust as vintage Era stuff..primarily because they are now boutique specialty items and not in the mainstream. ...I would recommend converting to Kt-88's...that will be expensive but will probably solve the issue.

[@acooper8910]

MIght have been worth checking the amp out with EL34's (which is what it was built for) to see if they too ran too hot at high volume.

[@BrentHutchinson]

Brilliant I wish I could be like Brad on the Phone!! Love you Brad! x

[@8o86]

"I have a youtube channel" *check* "Can I speak to your manager?" *check* boy this was embarrassing

[@terryharleyrides6109]

Your at fault here,...you missed the obvious problem from the start,...you need to apologize and own this one,...period.

[@georgeshaw8925]

How to turn your heavy metal 🤘 amp into a smooth jazz machine…. LOL 😂 Brad, my man, you was put between a rock in a hard place. Learned a lot, great video.

[@davidstorm4015]

I watched this all the way through and at the end the conclusion is that it's most likely that the amp is blowing the tubes, so there was probably nothing wrong with those Sovteks that failed? This makes a bit of a mockery of the first part of the video where you are ranting at the company that supplied the tubes. I agree a 90 days wholesale warranty is a bit farcical, but you really need to provide some balance here. Maybe you should have checked the readings on the tubes before you called the supplier?

[@troystermx4571]

This is what I love to see life in the real world take care as always your in them Dude!

[@williamsquires3070]

You’d have better odds of winning the lottery than having a grid-filament short. A cathode-filament short, yes, but a grid-filament short? No. The physical construction of the tube would pretty much prevent that: 1) the filament (heater) is usually coated with something like thorium oxide - not only to prevent it from shorting to the cathode sleeve - but to increase the efficiency of the thermionic emission, and 2) the filament, and it’s coating, are wound up in the cathode sleeve, with only a bit at the top and bottom showing. And all of these elements are held in place by the mica wafers so they don’t touch. Furthermore, the cathode sleeve itself often has a coating as well. The only way I can even imagine getting a heater-grid short is: 1) it was defective from the factory, 2) someone broke the tube and soldered a wire from the grid to a filament pin in the base of the tube (in which case, you have a much bigger problem!) or, 3) the tube got so hot from red-plating that the grid wire literally melted 🔥 and touched the filament support wire coming from the tube base. But, again, it’s much more likely to short yo the cathode sleeve. 🙂

[@SH-zj5pd]

I've had problems with Sovtek 6550's and excessive screen voltage. I've had better results using JJ KT88's in place of the Sovtek's.

[@umajunkcollector]

That's the part of the RISK, getting tubes? Brad should tell the dude that IF you want this amp, you're gonna pay like 200$ / tube, that's the esy it is, and why a good working amp like this can sell over 1k$. IT'S A BIG GAMBLE, this is why the tubes only have 90 days warranty. No more Radio Shack ""LIFETIME"" tubes, lol. Ted Nugent can afford new tubes for every concert.

[@cantyouhearmeknocking1961]

Man, I don't want to see you pissed! I want everybody to be happy all the time! You know, kum ba ya, Don't Worry Be Happy, & sh!t like that..

[@danielsaturnino5715]

The fuzzy sinewave is a high frequency oscilation impossed over the signal. You cant hear it but it burns stuff. Uncle Doug once had that issue on video. I once had a damn relay with no visible carbon tracking, I did scrape it alot and still had the coil leaking current to the switch side. Could your socket become conductive internaly also? Thanks for the video Brad

[@TheGuitologist]

I think that issue was the output tube already being intermittent, or lead dress related.

[@russellhltn1396]

Sure looks like parasitic oscillation to me. The only way you're going to get that smear is if there's some high frequency stuff mixed in. (Or very low frequency) Since that looked like a preamp stage, I'm not sure as you can blame the output tube. Fixing it by moving a wire would be consistent with a parasitic problem.

[@AuntAlnico4]

@Orandy oh, you are one of THOSE guys 🤣🤷‍♀️🥂

[@brucepickess8097]

@@russellhltn1396 I agree with your comment on possible hf oscillation. If he'd changed the scope triggering and expanded the time base that may well have indicated that. Definately hf oscillation can cause problems. I've experienced similar problems in hifi amps and they become high power oscillators drawing excessive current.

[@Ricksworldtv]

Sorry to see you have these type of problems. Back in the 70's I was a 2way tech and was grateful that the local RCA parts house treated me like royalty when it came to returns. That tube with the interment loose element is an obvious manufacturing defect. Your supplier should have treated you like you were an extension of their business and not like the end user. They have now made their bed and have lost your business for life. You might contact Sovtec directly, they might exchange them so they can have their techs examine them...

[@TheGuitologist]

Yep. Senseless move.

[@Ricksworldtv]

@@TheGuitologist On a funny note, I once had my 3-500 power tube develop a grid to cathode short in my Linear amplifier at my ham station. It was on standby for a 1/2 hr and looked over the Plate Voltage was sagging from 3200v to 2300v. I took a peek in the vent and the graphite anode was a white as the sun. Cost me $238 for a replacement. That old Amperex is now a Christmas ornament Lol...

[@ethanspaulding6067]

I disagree. What if Marshall is pushing beyond the spec of the tube? Is it still the tube manufacturers fault?

[@Johnny1.0]

@@ethanspaulding6067 Hmmm

[@scottdunn2178]

@@ethanspaulding6067 Some suggested reading; *The Tube Amp Book by Aspen Pittman *The Marshall Book by Mike Doyle These will explain the decision by the Marshall distributor in 1974 Rose-Morris to use GE 6550A tubes in all amps shipped to the US, Canada, and Japan. A Google search will also help.

[@jutukka]

The power supply of that amp is in fact too good. It does not sag and is able to deliver more power to those 6550s than they can dissipate.

[@TheGuitologist]

I agree. That's part of the problem. I also think the OT primary impedance might not be ideal for 6550.

[@jutukka]

@@TheGuitologist That is possible too. But when you look at the output tube load lines, most output stages seem to go easily to overheat zone but in real world don't, because the power supply is not rigid enough. Maybe just adding a 100-200 ohm power series resistor to the power supply to kind of emulate a tube rectifier could solve the problem and even could make the sound nicely compressed and make tubes last longer.

[@TheGuitologist]

Probably wouldn’t hurt.

[@jutukka]

@@TheGuitologist And as a bonus, it (series resistor) makes B+ filter caps last longer as well.

[@jutukka]

@@TheGuitologist If the plate to plate impedance of the OT is around 1750 ohms, which I presume, it is in fact too low for a 6550 quartet if B+ is more than 400V and does not sag at full power. The p to p load of 6550 quartet should be around 2000 -2500 ohms if plate voltages are over 450V because if the power supply does not sag, the load line goes over max allowed plate dissipation at low voltage side of the load line.

[@stevesuv]

So it was not bad tubes? Do you need to make an amends to your dealer? CALL Marshall and go off on them.

[@hairnation68]

I always cringe when people start dropping the Fbomb with customer service reps. They are trying to do there job. It’s yelling at a the guy who is just doing his job.

[@TheGuitologist]

There was no yelling. Standing up for oneself isn’t yelling. I’m not sure where this idea comes from that one isn’t allowed to express frustration in stark terms. It needs to change.

[@timothyb1559]

I'm sure the problem repairs suck for you but I enjoy these the most and learn a lot from them. I did arbitrations for one of the largest auto auctions in the western hemisphere so I know all about policy, however, at the end of the day all involved are *business partners.* Companies lose sight of that and it seems the focus on short-term gains over long-term prosperity is seeping into every facet of our society. It's a shame the world is turning dog-eat-dog more and more every day. Great vid - thank, Brad!

[@framusburns-hagstromiii808]

It's the Chinese business philosophy....do whatever it takes to make the product as cheaply as possible, treat your employees like dogs and your customers like contemptible suckers that exist only to be exploited then abandoned after the sale then take the Money and run denying any responsibility for poor product quality and lousy customer service. "So sorry..sucks To be you" Welcome to 21st century America!!

[@RHR-221b]

Good evening, Brad et al. Stay free. All the best. Rab 🍻 😎 🌠

[@thisisnotme7549]

So it wasn't the tubes and the whole seller CE, wasn't at fault? It's very confusing now!

[@johnsimms3957]

You have to put the new tubes in the amp as soon as possible. And then play and monitor the amp for a couple of hours. 90 days is a pretty good warranty period. Maybe you could try the new Tung-Sol or JJ 6550 tubes next time.

[@TheGuitologist]

A wholesaler who makes a 90 day warranty makes it almost impossible to keep stuff in stock. You end up eating your own stock.

[@barryjones872]

I changed 2 of my 6l6 ,s to el34,s in my mk4 boogie .these where genuine mesa tubes .stuck them in and one redplated .bought a pair of matched sovtec,s .perfect !!!!!

[@NoLandMandi]

at 5:00 as he kinda mentioned, removing that ring has nothing to do with this sort of job. it's useful when someone working around high current, low voltage circuits like a car or lithium batteries, and in that case they should remove ring or metal objects to prevent arcing and fire issues. if you touch anything live in any amp like this, you will know it with or without the ring I guaranty.

[@ghramsey1681]

I've worked on tube amps of my own scratch build as a hobby and had an occasion to tough a negative supply for a moment; probably -15 to -20 or so. That hurt. I've also touched charted filter caps. That hurt worse. | was always ultra careful around plate supplies though. And yeah metal anything is bad news around this level of voltage.

[@ctcards2636]

Im so happy that i use the different tubes I use today in my amps. Right now I have one amp thats running their "stock" type of tubes. But that amp is only running the stock power tubes 6L6. I converted all my 12ax7 preamps in my amps to 6n2p. I have a switch to go between 12ax7 and 6n2p. These preamp tubes are between $2-3 per tube and they sound every bit as good as brand new 12ax7 JJ, i think they sound better. They are also NOS military spec. But you need to do research and find out if these will 100% work with your amp, do your home work. Now in EL84 type amps im using 6p14p power tubes, once again Military Spec NOS and these are about $3-4 per tube. They sound amazing and i didnt have to mod my amps. I did mod my Blues Jrs tho so i have not tried the 6p14p in a Blues Jr that still has its bias wicked hot. Those come with 22k resistor and it runs EL84 style tubes too hot. Need a 27k or 32k replacement resistor and it cools bias down. For my 6L6 based amps ive been using 6p3s which the new amps most of the time need their bias to be cooled for these tubes. These sound wonderful and are $5-7 per tube for once again a Military Spec NOS. Reason im mentioning all this to yall is because when i have problems with my amps, im able to have problems like this video has without the hassle of pricey tubes to replace. If i need to put new tubes in my amp its like $18-25 total to put new tubes in the entire amp. That leaves me more $ to fix other parts of the amp etc. Im not saying this is for everyone, but Ive been burned buying expensive tubes and trying to deal with tech support with some of these companies, i wont name anyone companies tho :-P . When your repairing either your amp or someone elses and the company that sells ya a crap tube gives you BS like this and in the end you end up having to pay for it. At that point why am i fixing this amp ? Seriously. Dealing with BS from companies and the pricing forced me to find another way to keep my personal amp collection running. Take advantage of all the information out there folks and look for ways to make your life easier. Sometimes they take a little more work, but in the end youll be in a better place to deal with anything that comes up. I read up and asked about the preamp tubes and learned what i needed to know, same with the other tube types i mention above. But ask people if you have other options, because most of the time you do. Ive converted my amps and i have converted a few amps for people i know, who now have spread the word themselves. I was shocked when recently i saw how much it costs to retube a blues jr with 3 12ax7 JJ and 2 EL84 JJ tubes... $125-150+ WOWZA!!! Its a Blues Jr !!! How much does it cost to put new JJ tubes in a Twin !!. Was a reminder that im happy ive learned so much about the amps i use and ive asked questions and done the homework, its paying off right now. Id spend well over $1500 easily to retube my amps with say 6L6, EL84, 12AX7 etc. Brad ive dealt with your pain with trying to return bad tubes, those places have ya by the balls. Its really at their discretion if they will help you at all. They sold you a "working tube" and they act like if there is an issue its your fault and you did and blah blah blah and they stop listening to you. The guy on the phone is this video honestly stopped really listening to you at all early on. I dont think he wanted to bother his manager and knew he could play the card he did. Im too old for this shit and i dont think anyone should have to deal with people like this. Shame a lot of places are a no go on ordering stuff from after experiences like this. Now when i find a place that does go out of their way, i make sure i mention that and write a review now. I loved owning vintage amps, but now id rather build my amps or choose amps that i feel more comfortable traveling with. When your traveling with 2 1968 Twin Reverbs all original, there is always some in that crowd whos thinking "Thats a nice amp!" and i dont mean they are saying that in a good way. Ive had stuff stolen and i know 100s of musicians over their time on the road who have had stuff stolen. Thats why I dont tour with my Gibson custom shop guitars anymore. But their are many reasons ive done what ive done but seeing this amp drive ya nuts brad and then to get on the phone... reminded me of my own experiences.

[@ctcards2636]

Man i just finished watching the video and hot damn, i had to smoke a cig and breathe lol. That brought me back to some dark places lol. Brad bless your soul for putting yourself out there to try helping the owner of this. Sadly im not surprised by this and it seems to have only gotten worse. The days of the customer being right is out the window. Like now in this world your guilty until proven innocent. Its crazy. No one ever wants to take responsibility for anything anymore. But hey there are good people such as yourself out there and others that keep the world truly going round. ;-) Thanks for the video as always.

[@ctcards2636]

You mention people not wanting to buy tube amps anymore. Well i agree and thats why i changed my live setup. I use to use Twin Reverbs on tour. Thats how many tubes and i always traveled with spares. Thats a lot of $ in tubes. Well recently about a year ago I bought a SMS Classic Tube Preamp. Its based on a Twin Reverb preamp and has 2 12ax7 tubes. Thats it 2 tubes. And i have that running into a ART SLA-1 SS power amp. I have this setup in a rack head case that looks like a amp head. This amp to me sounds better than my 68 Twins, call me crazy, but until you try one of these thru the right power amp you may not believe me. But there are a lot of guitar players using this SMS CTP right now, well known touring musicians. But my point is im moving away from tubes as far as i can, i still dont like straight SS amps. But i found this setup and im glad i did. I travel with roughly 36 less tubes. I can run 12ax7s or with an adaptor i can run 6n2p preamp tubes. Both tube types sound awesome. But the day is coming where tubes are gonna really start disappearing from guitar amps because no one wants the hassle of dealing with the price, shitty customer service when theres a problem and the reliability issues. Now a days your basically buying a tube with no warranty, because if you buy them as spares and you dont use them for years, even if they sit in the box and you never remove them, they are out of warranty in 90 days. I guess you can pay even more to have them test it, but i dont know if i trust some of these places actually doing anything extra like that. I feel like once these places have your money they are done helping you out. They will help you out and go that extra mile if it means putting money in their pocket. But god forbid theres an issue, and with tubes there is gonna be issues. Thats like a company who makes light bulbs telling customers theres no way the bulbs they ordered could possibly break or be defective in shipping. Shit happens we live in a world where stuff happens, you have to meet people half way with this shit and these companies dont want to do and the people they are hiring these days are obviously not getting trained well, so this goes up in the company to the managers that some how are managers now. Basically weve allowed lazy people to legitimize being lazy, its the new norm. Business 101 is the customer is always right. Also just as Brad says, if the tube company never hears about problems from these companies, how will the company continue to build good tubes ? They need the feedback to know they had a problem and fix it. These sellers dont understand that, they are young and no one taught them the fundamentals of how this shit works. Sorry rant over haha

[@fireantsarestrange]

Well... from watching the whole thing... Your still driving the tubes past their specified limit. And yea I agree that he runs it all the way open. He still will too.

[@TheGuitologist]

I warned him not to exceed 7 in the Master for long and to use a fan.

[@cchan11cc]

You would be a great amp builder. You know more than most techs.

[@amphetamineblue4172]

I kind of see their point as well. They don't know that amp hasn't been run cranked 8 hours a day in a studio since fitting, or the guys soundproofed basement. You only have his word the tubes blew at gigs. I don't think any retailer would replace it for free after 18 months

[@TheGuitologist]

They aren't retail. They're wholesale. I'm the retailer in this situation.

[@amphetamineblue4172]

@@TheGuitologist Mistype, retail or wholesale though anyone selling something is going to have a limited returns period on it

[@amphetamineblue4172]

@@TheGuitologist My point still stands though that after 18 months with only the customers word on how the part has been treated... It's a shame you are getting stiffed, but that is part of business we all have to deal with and sometimes have to absorb

[@ghramsey1681]

@@amphetamineblue4172 *In 'De-Fense' voice from Falling Down* "Did you ever hear the expression : 'The Customer is ALWAYS right' ? Well here I am... I'm the customer!" Kidding aside I agree with Brad. They should have replaced the tube. Or handled the situation as a discounted return/exchange as a compromise.

[@The1stLumiens]

I'll give you an even older saying - "Caveat emptor."

[@BustedJunkStudio]

I'm a little confused Brad, ain't the 2204 a 50 watt head and the 2203 a 100 watt head (2 power tubes vs 4)? Just wondering because I have a 2203 story coming up. I know Marshall has a lot of models, maybe they changed things up?

[@christopherwoods6]

Yes

[@TheGuitologist]

You're right, I screwed up the title. I'll fix.

[@RHR-221b]

@@TheGuitologist Appreciated, B. 🍻 😎

[@jameseberhard7457]

Hey Brad keep an eye on Brimar, there are a group of people over here in England trying to bring back British valve production in case you hadn't already heard. They'll always be a market for valve amps, theres just no soul in a fucking kemper 😆

[@fongy200]

That's right James. I use a Kemper but you can't beat a valve amp the Kemper for me is convenience. My AC30, JTM45 and other amps that are valve state along with my Guitars are my pride and joy. I agree there's no soul in a Kemper it's an amazing piece of tech but there's something not included with modeling gear. I like yourself am in the UK and I've been using a load of nos Mallards and Sovteks that I got from an Auction, massive job lot all sizes, I proper dropped on they came out of an old Radio Rentals store in Mold, Wales from what I can gather. Anyway sorry for the waffling but I agree and the Brimar's are decent valves.

[@nickdevriese]

Really? Brimar is coming back? Nice.

[@jameseberhard7457]

@@nickdevriese hopefully so mate, they have started producing ecc81s in the britian I think, so hopefully they'll expand the range to include so more common models

[@jameseberhard7457]

@@fongy200 that's it man nothing can replace the experience and inspiration attributed to playing a big bold valve amp, the spirit is what makes the music, musical

[@andomi]

When I saw you taking out the last tube from.the socket an hit the cabinet, I remembered once I pulled out an EL34 with the same system and the top of the bulb hit the tip of a screw inside and the tube broke.

[@Hoagiemon]

“Pretty soon people ain’t gonna want to buy tube amps” . I reach that point years ago and never looked back. My lead guitarist said he’d never not play tubes. A month ago he retired his Boogie and now plays a Quilter and loves the tone/less weigh. Sometimes change isn’t a bad thing. On the other hand, I have a expensive powered PA speaker outta warranty that’s blown the woofer and power board and it cost more to replace the parts than it’s now worth. That’s life.

[@Dennis-mq6or]

If you can remember the rule never to mix tubes and printed circuit boards in the same chassis where the tubes heat the circuit boards so much that the extreme thermal cycles cause the circuit board vias, and sometimes even the copper tracks themselves to develop microcracks that are a technicians nightmare to troubleshoot, tubes can be very reliable. New high temperature (108 deg C) rated capacitors, and poly coupling capacitors eliminate the weakest link in any old tube amp.; allowing them to provide reliable service for decades without any part changes. I have equipment on the test bench that was refurbished (with new tubes where they were needed) in the mid 60's, never ever turned off, and have never replaced a tube, (or any other part), in any of them.. My test equipment is left on 24 hours a day, 7 days a week, because all test equipment 'drifts', both tube type and solid state type...and that was the best way I ever found to 'tame' that drift.... 24/7 for 60 years and those tubes are still working fine.....

[@RickP654]

Thanks Brad, I really enjoy your videos. I hope you stay active in this field of employment and sharing with all of us your repairs. I think I would remind him he needs to jam with it every day so that if it breaks again it will fit the parameters of the 90 day warranty with the company that sold him the tubes to start with. Good luck and God bless.

[@ringostarr4520]

I know some techs will require that the customer purchase the tubes they want to install. That way it is the customer that is directly responsible for the warranty of the tubes. Those techs don’t do that for all tube types but rather for these specific situations for these robust expensive cases. Think SVT with a sextet of 6550’s. It’s getting harder and harder to find reliable sets of tubes that are matched for such amplifiers.

[@rads89stang97]

What was your ac measurement at speaker at full load test and how much was it drawing... Not at idle.. the amp was feeding back at one part in your vid.. have ohmed out the feedback circuit...and pot... Just wondering? And tube sockets!! I bang on them with drum stick! And I always put a tube in.. then go to bottom and make sure all pins feel seated. U be surprised how many get pushed down deep barley making connection with the pins.. and phenolic sockets get ! Hot !!! And crack = arc = more tubes! I think tube sockets is the problem.. but if amp is feeding back on itself.. that's another prob.. keep us informed. I'm curious...

[@hestheMaster]

Replace the tubes and watch power output on a Variac at 60% to 70% power and see what it does. Might have an issue with the tube sockets too. Looks like you have spent a lot of time on it. 1800 on the screens on those new Sovteks probably may help. Crappy customer service really ticks us all off but seems to be the norm. Intermittent issues can drive you more crazy than whatever is passing for normal today!

[@KeritechElectronics]

Awwww. That phone talk reminds me of IT people playing pranks on tech support scammers.

[@TheTrashologist]

You could do like the guys I work with, if a truck keeps blowing a 10amp fuse they replace it with a 15-20amp. That’s the proper way to fix it, Right?

[@camilo1455]

Well, there's foil...

[@TheTrashologist]

@@camilo1455 when all else fails jamb a paper clip in

[@gford8551]

I'm a fan of the foil in a cigarette pack lol

[@RHR-221b]

@@gford8551 And a fire extinguisher? 🍻😎

[@garymallard4699]

You can fix it Permanently by cutting a small bolt to use as a Fuse!! Never worry about Restrictions again!!

[@ethanspaulding6067]

Good job on the Grid leak swap to 82k. Ideally, you would put them at 25K, but that will be hard for the phase inverter to drive. Just count on the grid leak current (positive) countering your -Vbias voltage. I would just try it at 20-25mA/tube. Maybe it isn't as bad as you think. Go form there. At 70%, you are asking for trouble as you should count on the bias climbing positive as it warms up. It's not tubesandmores fault, or the fault of the 6550's, as Marshall is pushing the spec sheet. My 6550 spec sheet says 50k max grid leak for fixed bias/tube, so 82k is equivalent to 164k/tube. EL34's are always an option too.

[@jesse75]

This guy's ego got in the way of good judgement.

[@UzerneigmROSE]

No matter what’s the fault the fact that you’re an exemplar customer should warrant better customer service.

[@Hungry_Hunter]

You need to rebuild the Bias circuit to provide some extra current capacity by increasing the two 10uf 100v caps in the Bias supply to 33uf 100v and reduce the series resistance after the transformer before the diode from 10k to 5k which I do by adding another 10k resistor in parallel. The 6550's need a greater amount of Bias as they age typically around 64-ve at grid 1. Over time the caps in the bias supply dry out and the little bias adjustment pot develops a higher resistance over time . I usually replace the bias pot while I'm in there. Increasing the Grid 2 resistors from 1k 1w to 1.5k or 2.2k will help the 6550's last longer and there is no difference to the sound of the amp.... It's a Marshall after all so its all about distortion and trying to keep the opt from cooking. Your calculations won't mean squat and the owner of one of these will never play it easy. Good luck Choda boy.

[@ghramsey1681]

This was his 2nd time with it on the bench. He might have re-capped it the first time already. Those filter 'cans' all looked new. The e-lytics also looked new close up. The one by the bias adjust pot said 10uv/160v.

[@Hungry_Hunter]

@@ghramsey1681 Still need more capacity 10uf is just not enough when the 6550's start to draw current.

[@scarmyguitar]

Was working sorry I missed this live but man you had me cracking up a couple of times

[@chuckyz2]

So did changing the resistors to 82 lower the output wattage. Your tech said those amps are not happy with anything other than 82. If that thing was making too much power because of the 150's that could melt a good tube, right? And running them at higher than they are rated could find different weakest spots in the tube causing failures in more than just one way? I have a feeling it will be fine now.

[@atech9020]

Could it be ultrasonic oscillation? The " Flashback " video makes me think oscillation. Now why it goes away as volume goes up is interesting, but still a possibility.

[@SIXSTRING63]

I saw what looked like parasitic oscillation too in that earlier video. He needs to invest in a cheap digital scope to freeze frame the trace and zoom in and see the oscillation and the frequency. You can get a decent new digital scope cheaper than a beat used 40 year old Tektronix scope. I have two nice old Teks I love but use my Rigol 1054EZ for zooming in on noise. I love all the read outs the new scopes have too.

[@aristocaster]

Wow, i watched an hour before you changed the resistors that you had noticed that they are wrong value hour earlier, and even after that there is a problem that never get solved if you have to tell client not to turn the volume past 7. So it is not fixed even.

[@bobboitt3126]

One word TAD . Tube Amp Doctor tubes are tested and burned in with 6 month warranty.

[@1tdillon]

Brad...great vid as usual. Always learn a ton watching you diagnose amps. Something I noticed, I don't believe I've ever seen you feature an original Silver Jube repair or mod on your channel. Would love to see you pull the guts apart on one of those bad boys.

[@charleslauter5035]

Was this amplifier designed for the output tubes you are using? Do you have resistors from each cathode to ground to balance the load? Does each conle

[@hrsey71]

haha funny, i was just watching the older video on this amp to see your PPIMV wiring. and BOOM! here it is again

[@kenpowilliamson]

Interesting how the two 150K ohm resistors which value is shown as is on the schematic is shown as 82K ohm on the board.

[@anks888]

Oscillation because of the routing of what I think is a master volume and neg feedback mod is probably what's happening in the video you show early on

[@anks888]

Later on it's obviously a send and return

[@olecranonrebellion9976]

You should contact Sovtek, and im sure they'd comp the tube after seeing this.

[@riffsnreviews]

Yep not a problem you want to see, burning 200 usd of tubes all the time, good job they weren't winged Cs ! Brad, I was curious, how's the reaction in general when the guys have to bring back their amps multiple times, are they mostly pissed off or just cool about it ? And what's the average threshold from going from cool to pissed off, 1st return, 2nd ?... And in this case how do you know it's not user error ?... moving a hot amp ? I mean you have to believe the person who says "oh yeah it failed mid gig by itself"... Not a nice position for a repair dude. On a side note i'm only 14min in so maybe that question was answered, but it's also a general question, how would you know if someone is BSing you or not ? Coz one has to admit the most common reason for premature tube failure is hurrying up moving your gear after a gig (not having the luxury of waiting for shit to cool down while you drink a vodka or 10), it's happened to me, not just once, and they don't always fail the same way, microphonic, shorting or air, but 99% of the time I know why something has failed

[@riffsnreviews]

Lol ok, got to the phone call, they're idiots, independent of what actually happened, it's retarded from them to not want to lose 50 usd on an order when you're dealing with a long term client... I'm in the import export business (and on way higher invoices), I deal with things like that I never let my clients hanging, sometimes you don't know if it's a user problem or a manufacturer problem, but when you sell things you put in a provision on your price for things like that, and if it's a problem that happens out of warranty that shouldn't happen (out of the normal standards) I fix the problem I go to my supplier to say ok you're giving me a discount on my next order i've had problems that happen out of warranty that should not happen, I don't put it on my client That being said, tubes are a more delicate matter... EDIT : Oh shit that's the only 2 returns you would have done since 2014 ! And so actually only one comped tube since 2014, they're fucking crazy ! For all managers out there, this is a great example of what not to do if your're managing a company

[@xWonderxBreadx]

As someone who is backlisted for 6550s until next March (estimated), it physically hurts to hear anytime an amp is blowing them. I've got (3) SVT-CLs and a 2203 in the shop that are obnoxious paperweights until then

[@axandio]

"It's not my fault...." Dude I was in 3rd grade when I found out life is not fair. The girl that asked to be my "girlfriend" (we'd hold hands on the playground but I started missing my friends, I "broke up" by saying, I don't want to be your boyfriend, I just want to hang out with my friends..) she ran to the Duty Teacher and said I hit her. I did not. But nevertheless I feel my ear being tugged suddenly and an angry woman telling me I'm going see the Principal. I actually had to grab my ankles and take 3 smacks from a leather belt to my ass and was completely innocent.

[@tomleary121257]

Aloha from Hawaii it was great to see you take a full circle you wanted those tubes and they wouldn't give them I realized to observe pain in the ass you never know one blows it f**** the rest but it was great because they turn you down and then you realize you know you weren't going to get it we all were rooting for you

[@salossi]

Without having watched your whole video: But among amptechs, who are working a lot with 6550-amps (I used to work in an authorised Ampeg repairshop and we serviced A LOT of SVTs), it is a common issue, that these kind of tube-retainers cause tiny cracks in the glass, resulting in tubes loosing their vacuum. We modded EVERY SINGLE of these retainers by covering the spot, where the spring is attatched to the retainer with shrink tube. I guess, at least, this will be part of your problem.

[@mk.nonamenation]

I had that