This Amp is an ABOMINATION! - Mesa Boogie Repair HORROR SHOW (PART 2)

[@borz666]

I would also test it in its cabinet. Your are letting a lot of heat out of the top of the chassis. plus the vibrations from being played from the speaker. Inconvenient i know but you need to test as it would be used,

[@robertsmiczsmiczamplificat593]

borz666 . Exactly. I agree. I always do a several hour test in the cab for max heat build up before it’s officially repaired. Thats Just me.

[@rebeccarosser9816]

I agree as well. in the cab. pushed! the vibrations could contribute if something is breaking the circuit

[@hallanvaara6106]

This

[@83roadstar]

I have a 1991 Studio 22+ ,tubes have been changed routinely....Mesa Boogie Rules! I keep it simple,change the tubes and play!!

[@TheAndrewWorleyable]

I spent the last 10 years as a residential Maintenance Supervisor but I've always played guitar as well. I know that troubleshooting is 70% of a job typically. It's always a great joy watching your SPF's and repair videos. I've spent my entire life hanging around with folks like you, even though I'll be 30 this month. You are extremely relevant, and your content is ALWAYS highly anticipated in my life. Thank you for everything Brad, much love from Oregon brother!😎🤘

[@normlenhart1310]

Brad, you electrical wizards have my complete respect. I have always been a car/metal fab guy for my recreational hobbies and have even done ground-up's on rust buckets with little drama. But as soon as I have to get behind a dash and sort out a wiring/electrical problem, I am all but lost. After a few decades I have resigned myself to the fact that it's never gonna sink in. I can't imagine dealing with an intermittent issue in something this small/delicate. I'd be crazy 10 min. in.

[@UncleDoug]

I've had similar occurrences recently, and in each case it was due to faulty coupling caps, which allow DC to pass to the next tube's grid and alter its bias. If you're monitoring the tube's plate current, it seems to "run away", until you either pull the plug or eventually smoke the tube. I believe the overheating cap(s) you commented on were coupling caps.

[@paulcalmond]

Always better to be certain your theory of the faulty part is correct. Replacement of parts you think are faulty leads to your customer paying for unnecessary work in addition to paying for what needs to be done, plus your reputation isn't enhanced by this approach.

[@tronics666]

Look for the smoke! That's where to start. ;-)

[@Renshen1957]

@@tronics666LOL, and so very true…

[@Renshen1957]

PCB are crap. Yes there were good amps with PCB Early Ampeg, but Fender never made a PCB for its HotRod amps that last with daily performance with a gigging musician, maybe 5 years

[@UncleDoug]

Thanks for sharing this with us, R.@@Renshen1957

[@sgriffith2941]

Before me there was a pile of amp chassis that were not worth repair or parts issues at the time several feet tall and as wide as the room. Hundreds of them. My job was strip them of useable parts. It looked like a lifetime job. The smell was also unforgettable. So as you struggle today remember many before you have had problems with repair and cost Many amps in that time were simply thrown in garbage after being stripped. Mostly cheaper brands whose name is all but lost in memories. Thanks for the hanging in there on this one. It's how one learns good job !

[@gilmacevers253]

Whenever i'm feeling blue, i like to watch these Mesa videos...lol

[@richard66754]

Years ago I had a Mesa Boogie rectoverb combo that kept blowing power tubes, then had channel switching problems. I was the second owner, with no schematics and lack of resolve for fucking with the amp. There’s no accounting for how it was maintained before I owned it. I called Mesa and they told me to pull the chassis and tubes and send it to them for repair. They only asked that I pay for tubes and shipping. I got it back with all newer version boards installed. How nice is that! I finally sold it a few years back, and it was still an absolute fucking tank! The guy I sold it to still plays the living hell out of it.😆

[@abubakr6939]

Richard Bowles wow talk about customer service!

[@edfrench6503]

Design failure 101. How to make a tube amp nightmare - have the tubes upside down; heat rises and slowly cooks your amp while you play. Fender, Gibson, etc. Learned this lesson the hard way.

[@amaurythewarrior]

i've never heard of a fender combo with the tubes not hanging

[@joemiller9009]

Better you than me. I stopped servicing Mesa Boogies a couple years ago. They just eat up time. Got tired of feeling lucky to break even on them. Over complicated designs stuffed into tight spaces. Stacked pcbs. More FETs than you can shake a stick at. Excessive heat build-up. I feel bad for you man. For me, this just reinforces my decision to shun Mesa Boogies from my bench. Thanks Brad

[@DeadKoby]

It's a Mess-o-Boogers.... the joy of working on one of those...

[@djstringsmusic2994]

As much as I know it sucks for you I enjoy watching a master work on something truly challenging

[@TheGuitologist]

Thanks for watching.

[@DavidMFChapman]

If you change a bunch of components all at once, and it works, you don’t really know which one had failed.

[@vk3fbab]

Yes but imagine how long it would take to fix the issue. I prefer to know what a problem is but sometimes you just can't afford that luxury.

[@DavidMFChapman]

bravo bravo I thought of that, but it might be worth the investment if it’s a systematic problem.

[@underpressureman]

@@DavidMFChapman I have a Mesa 50cal+ I basically got for nothing because the dude said he took it to a tech like 3 times in about a year and it just kept failing, so at that point it's like buddy obviously felt the amp was just a burden lol, but Im hoping i can come across a tech who can fix it! Or just change things out and hope it works lol, but I don't want to fall in the same cycle of spending money and have it keep systematically fail! The thing that's wierdest about it all is the guy won't tell me who the tech was but he can't tell me what the problems were so I don't know where to start. So either he's lying about even taking it to a tech, or he's telling the truth but it doesn't give me a very good place of where to start.

[@ETILHK54]

You can test them, if it's value is off from what is should be, then that's the one.

[@usoppbarbosa981]

@@ETILHK54 unfortunately it's not always that simple. some components can measure fine with a tiny wee multimeter, and fail in smoke when you apply power to them (tantalum caps to the face). When they get warm, things move too. Poor solder joints, crusty sockets, ceramic caps, resistors.. all can measure great and be the cause of your problem, besides not all components can be measured precisely in circuit.

[@MoOvertones]

I’ve been a technician for the phone company for 18 yrs and I can really appreciate this video. Trying to find intermittent trouble is every techs FAVORITE NIGHTMARE!😁.

[@archiguitarchi]

I've been playing lead since 1963 and have owned dozens of amplifiers, some extremely nice ones. The two worst were a Mesa Nomad 40 that ATE EL84 tubes and had waaaaay too many switches and knobs, and more recently a Mesa 50 Caliber+ EL84 version which was unrepairable. Its problem was red plating that no local tech could solve. NEVER AGAIN.

[@thatampguy]

Your local techs were not competent!

[@youbecha64]

Did you put the thermal camera on those caps after you changed them out?

[@AndGuitar]

youbecha64 that was my thought as well.

[@tubejoust]

completely build the bias supply and circuit off that main board. when troubleshooting , use two meters to monitor the bias on both sides at the same time. Its a very bad idea to have +400 or more volts very close to a negative voltage on a PC board. Marshalls were plagued with this problem and the fix was to drill out the board from around the bias pin and run flying leads to it. I have seen that cracked board scenario as well quite a lot. Using cheap PCB material with thin copper cladding is a bad idea but bean counters love it. Also that "bubbling" you say you saw is often solder flowed under the mask. not usually air gaps. WHat i often do is scrape off the mask from a board and lay down a bare copper wire over the trace and solder it along the trace to 1, ensure its continuity and 2, beef up its current carrying ability. This would work well on that output tube board and save all the drilling but i would have still isolated teh bias pin and put that circuit on a daughter board or flying leads....my 2¢

[@jenniferwhitewolf3784]

Barry Beadman Yes! I have done that at times when a board more or less ‘must’ be kept... It is appalling how shitty some boards are laid out without regard to high voltage spacing, and current capacity of the trace foil. Too many idiots doing the work.

[@1961jscofield]

Your close up camera detail has gotten far improved since the upgrades. Nicely done.

[@sandiesjoys9777]

I have had 2 mesas. Both had issues that were very difficult to find. On a 50 watt Son of Boogie, it would intermittently cut out while playing but when the chassis was on the bench, it worked perfectly. I found a resistor covered in a glob that I used a dental pick and found it wasn't soldered in. After that, the amp worked. The second amp, I sent back to mesa and they had for several weeks and sent back. Same issue, and an unsoldered resistor.

[@the_grube5782]

I spent months trying to get the hum out of a simul 290 power amp. I spoke to Mesa and their response was "it's supposed to do that". When you switch the modern function on it would hum, it adds a cap into a feedback loop and acts as an oscillator. That's just one example, I have numerous Mesa repair nightmares. It doesn't help the schematics are inaccurate. Just look at the layout of the PCB it's a mess. Looks like they threw components at the board and where they landed that's where they etched traces.

[@Geerladenlad]

If this amp comes back again he's going to take it out in a field and beat the hell out of it like they did to The copier on Office space.

[@dnantis]

yeah !!!!

[@paulcalmond]

Or consider that three attempts to fix the same problem could reflect negatively on diagnostic abilities more than quality of design and manufacture.

[@michel333100]

Hi Brad, I just thought that I'd comment on Mesa amps that I have owned and a DC3 Mesa that a friend of mine owns. I have owned a Mesa Tremoverb amp since 1995. Bought new here in Canada. Cost me a king's ransome to buy here. I have had nothing but trouble with this amp since the day I bought it. Just recently sent it all the back to California for repair. The trouble with Mesa amps, is when something does go south mate, you're pretty much screwed trying to find someone to repair it. PC boards are nothing but trouble in that respect. I currently own two Ceriatone amps and they are both point to point wired. Makes repairs relatively easy. Never had any problem with Nike's amps from Ceriatone. My Tremoverb is back from Petaluma and it does work now, but the noise floor is horrible. It has Voodoo amp mods from Voodoo amps. The amp doesn't sound bad, but the noise floor is pretty bad. I still think that this amp should be a boat anchor. I would never buy another Boogie. Too fizzy sounding in the red channel stock, like a can of bees. The amp is also way too brassy and compressed sounding. I also have a Mesa Revolver Leslie speaker that seems to be going south. A Canadian actually invented this Leslie. It's great when working well. Their amp cabs are very well built. The seems like It's very well built, but the sound is not something that I personally like. I also think that dealing with Rich at Mesa sucks. You would think that they would have tried to do something about the noise floor problem. Do you know Brad, whether or not you can use GZ34 rectifier valves in a Mesa Tremoverb amp? My friend also has a Mesa DC3 with nothing but problems.The board that those valves were mounted on are terrible. Fender builds the same shite.Take care , love your videos Thanks from Michael Newell from Niagara Falls, Ontario, Canada

[@FloridaManMatty]

Brad, man, thank you for doing these videos. No shit, watching your process has helped me be a better paramedic. I even used parts from a couple of your videos to teach my medic students. Watching you trouble shoot and rule things out is essentially the same kind of differential diagnosis process we use. You and the old NPR program Car Talk are perfect examples of how to diagnose through elimination. You’re saving lives, brother!!

[@bigfootingermany]

Matthew do you guys just change parts until "it" works again too? lol

[@larryfried7742]

Hey Matthew...I certainly hope you don't use complete process of elimination with your job...and the idea of you with a solder sucker in your hand has to terrify your patients. :-) BTW.. I been working on electronics , for like 50 years now and I really can't see you doing anything else to check for loss of bias. Just the one, as someone previously said. A heat gun, put it back in the cabinet or case and move it around like the owner would do with gigs. You did a great job changing out that funky tube board with hard wiring. Definitely a weak point in the design. Those tubes get pretty hot for a normal guitar amp's baseup placement. Crack in the board wold be a real PITA. Reminds me of a few SVT's I've worked on. Everything has to come out , and I mean everything to change the cave type jacks. Inputs and outputs cheap plastic sealed jacks CRAP! in such an expensive amp. no!................arg! Of course Ampeg isn't owned by the original company anymore. And as you said about mesa boogie Customer service is super over there.

[@TonySkiens]

Brad is Fran!! I've never saw them in the same room!

[@kalidesu]

Brad is also Lorde...

[@Scottie_S]

All we need now is for Fran to put the 'twang' in her voice to impersonate Brad!

[@dmitryshtshitkov710]

Check the coupling caps you removed for leakage. Looks like a textbook example of a leaky cap.

[@jixxxxer17]

My Mesa Boogie 50 cal Plus has been a bad bad dog to fix, I paid $475 for the amp used on Ebay and i have already sunk $875 into repairs and it still doesn't work right . The issues a) the sound cuts out and sounded harsh harsh harsh and of course this was intermittently b) when i turn the amp on all you hear is loud static and crackling noise c) when i use the foot switch to go between the clean and dirty channel there is a huge huge spike in volume, the volume spike could knock a freight train of the tracks, i swear. THE FIRST REPAIR GUY replaced many of the smaller tubes, not the power tubes, repaired many cold solder cracks, and some general cleaning of electronic parts inside, cost $275. THE SECOND GUY replaced all the capacitors and replaced the two power tubes with 2 used Groove Tubes, that's right this guy replaced old tubes with used tubes that he said could not guarantee how long they would last. for his work he charged me $600 . Between the two guys it cost me total of $875 and the amp is still not working right. I made a couple phone calls to Mesa Boogie, THEY COULDN'T HAVE BEEN NICER , REALLY TOOK THE TIME TO TRY AND HELP ME OVER THE PHONE, BUT IN THE END AMP STILL NOT WORKING CORRECTLY. I can't even sell it if i wanted to the way it crackles and hisses . Anyway, I don't know what to do with it other than taking the Chassis out and sending to Boogie , but that will be expensive, i like the amp but damn there comes a time to walk away .maybe i will put it on the front lawn with a " FREE " sign on it.

[@abubakr6939]

Moda Mont you should have just sent it to Mesa in the first place

[@jixxxxer17]

@@abubakr6939 I THINK YOU ARE RIGHT MY MISTAKE LIVE AND LEARN I STILL HAVE IT AND IT JUST SITS THERE COLLECTING DUST NOW .

[@markhoskins]

This is why I like simple amps like a Plexi Marshall or a Tweed Fender. Not much to go wrong and if it does it's pretty obvious. :)

[@audiotechlabs4650]

Great to see your expertise again on amp service! Not that I don't like your other videos, they are great to! Mesa should go back, at least once, and rebuild a Princeton amp chassis with a Twin-Reverb circuit or Super-Reverb circuit and put a 12 inch 100 watt speaker in the cabinet like he did for Jerry Garcia! That was his finest hour! Love ya Brad! Thanxz

[@tylerangle1990]

Vibrations, all my combo amps seem to develop issues from constantly being in a vibrating box with a loud speaker. My guess would be something to do with that if you haven’t already got it fixed. Also I’d check it with the thermal imager again and see if the new caps are running cooler or not. Enjoy seeing videos like this. I don’t really repair amps but I have an interest in it and have done some electronic repairs on other things in the past. I like that you let people see how challenging things like this can be to find and repair. Intermittent problems on anything are a real pain to deal with.

[@stephenlord8719]

I know many have commented on your drilling and your drill. I have a riveted-in, broken socket to replace, on my bench. So, I'll be doing some minor drilling on a fully loaded wired chassis. My tip is--and I've never used a "step" drill bit (so, this may not be as effective for that)--always use a drop or two of oil when drilling metal. Put it on the bit or the piece. You can actually use Vaseline--I kid you not--it will make the job smoother, the flakes will be more like metal ribbons, the hole will have less burrs and it will make your drill bit last longer. I never drill metal without lubrication. I keep a small lever-pump style dispenser, filled with Marvel Mystery Oil, in the shop for small lubrication tasks like drilling, etc. But the Vaseline trick works when you don't want liquid running into other parts, or you're drilling overhead, or outside on a ladder. It melts and lubricates and makes the drill job much cleaner and smoother. As for the amp, some players tilt their amps and that could cause areas to heat up that normally wouldn't when you have it horizontal on the bench.That amp, when tilted would cause heat to flow to the big board? So, you might try running it tilted, for an hour or two--or ask the player how they configure the rig. Do they stack shit on top? etc.

[@adamgiansiracusa5068]

I bought one of the first Mark 1 amps from Prune Music in Mill Valley in about 1976. Biggest headache ever produced by mankind. Sal, at Prune, had to service it several times until I gave up and sold it. And that amp was way more simple than this thing.

[@decomputerleraarable]

Hi, did you checked the removed components? You'v got that little gizmo that is right for that job. Rob

[@JRP3music]

I have a Mesa Nomad 100. I have been having an issue with feedback at random times on ch. 3. I noticed even when I turn the volume knob off it still has feedback unless I switch to ch. 1 Clean. After my gig, I changed out V3 & V4 to see if it was a microphonic issue. Then, I discovered that 2 of my 6L6 tubes guide pins broke. I replaced those, then suddenly the clean channel stopped working? V1 was difficult to get to and the tube was not going in the socket like the other sockets. The feedback situation is weird, because I use a noise gate at the input and at the fx loop. I removed all the gates, switched out V1 numerous times. Got the clean channel back briefly. I got my amp used almost a year and a half ago. I had to replace V1 about 3 months in to owning it. I only run it 50 watts. This amp seemed to be barely used when I got it. I do not like the reverb that is built in. I have been thinking of removing it. I was wondering if it could be used like another fx loop. For example sending another EQ to any combination of the channels. Also, there is another piece of wood behind the baffle. I am wondering if it is possible to remove it to improve access to the preamp tubes. I don't like having to flip the amp upside down to access the tubes. The reverb tank removed may improve access. I could put a panel over the reverb tanks cavity. I think that all is wrong is the V1 socket. Maybe a new set of preamp tubes. Will removing the reverb tank effect the amp?

[@mdzacharias]

I think you were definitely on track regarding that cap that was getting warm on it's own. That should never happen, and since one end was to a high positive voltage, leakage there would take out that portion of the negative bias. I think you got it dude! Thumbs up!

[@DrWatts-bi1jv]

A hot cap is a shit cap 🔥

[@1Dougloid]

I won't touch 'em any more. Life is too short to be unhappy. The last one that showed up had switching problems. I counted 33 knobs and seventeen relays and only G-d knows how many FETs that represent potential failure points not to mention the three rectifier tubes and what-six or eight power tubes?. Away it went to Petaluma with my blessings.

[@jerrybotte5268]

I had the issue of red plating on my DC-3 not long after I bought it in the late 80's and spoke to Mesa Support and they told me the clip retainers sometimes short the contacts, I removed them and never had that problem again. Not sure that was the issue here but wanted to share my experience.

[@tubestransistorschannel]

I liked the PTP wiring for the output stage. I use same multiple-diameter cutter @22 mm step for 9-pin sockets.

[@bindiki]

Dude, have you ever worked on a Mesa royal Atlantic? And is there anywhere you can think of to get my hands on a schematic. Having a few problems.

[@azstratus1]

Man this is some incredible work holy smoke.

[@duanecook4227]

You could try heat gun (or hairdryer) and freeze spray routine to try an force a failure. Got to be careful with the heat obviously. Generally a technique that would be more useful for design debug as you can afford to kill a unit.

[@rogerw9840]

Aw, I just wrote that in another comment. :) Didn't see yours.

[@MarksmanGuitar]

I would try to cover it up to simulate normal operating heat , since its out of the cab . I hope this helps !

[@scottsagor674]

Did the power consumption go down when the "hot board" was replaced with the hand wire (awesome) rebuild? -thanks

[@leepshin]

The legend that is Walter Trout had one of these start misbehaving during his Glasgow gig just last week. He most definately was "not" a happy camper. LOL

[@youztuber5000]

What. A. Nightmare. You're a total pro.

[@123spleege]

Man, I was going to dump my old Dean Markley CD 120. I am 3 inches shorter just from carrying the monster around. But after opening it up to compare build with your videos of the Mesa's, I have apologized profusely, say nice things to it constantly and occasionally smoke a bowl with it. We're friends again.

[@cyanidejunkie]

Love Brad, love my Boogie, but extra bonus points for the L.O.T.R. Reference.

[@philipdecatanzaro1822]

Finally an amp video. Been waiting for weeks.

[@merrittderr9708]

I'd suggest 2 things. One, get a drill press. Two, don't drill metal shavings all over your ELECTRONICS work bench. I enjoy your repair videos and have been watching them for a couple of years. Your SPF and rant videos, not so much. Hope the repairs work this time.

[@markmcqueen1882]

Don't really need a drill press...just some way to keep the chassis from flopping around ...like a couple of quick clamps. :)

[@merrittderr9708]

From a safety standpoint, the drill press provides much better control, avoiding the handle windup on the hand drill. Also, with a drill press it is much easier to control the depth step that you want to reach. I've drilled a lot of holes in a lot of chassis and wouldn't do it without the drill press.

[@markmcqueen1882]

@@merrittderr9708 I agree a drill press would be best. Just saying that securing the chassis would have made it a lot easier with the hand drill.

[@billb7735]

and if i have to drill an assembled amp, i mask and cover surrounding items before i drill so shavings can't get into something.

[@merrittderr9708]

@@billb7735 and hopefully move it off your primary electronics bench as well :o)

[@Chrispy_tV]

What did the bias supply caps look like in the thermal camera after replacement? Were they still getting as hot as they were prior to replacement? How about tube temperatures? Did they even out after setting bias and replacement of bias supply components? Or are they still uneven? I think these characteristics could be telling as to whether the amplifier is "cured" or simply seems ok and is just a ticking time bomb.

[@74dartman13]

Intermittent problems are a pain in the butt! I can remember doing service work and driving 2 hours to a job, to find the equipment was working fine. Drove back to the shop to be told it failed again! This was before cell phones. Then took another 2 hour drive...insanity!😵

[@InTheSh8]

Ur not serious! Did you find the issue, though?

[@74dartman13]

@@InTheSh8 ya, after messing with all the adjustments...was a commercial gas fryer that was sold before all the bugs were worked out of it! Factories did it all the time!☺

[@LowEndStrings]

I’ve never read any good stories about a Mesa repair. Now I know why. That must suck to repair.

[@Starcrunch72]

Yeah, Mesas are bad, but look at the inside of say a '74 Ampeg VT-40...I had no idea how they put that together, let alone how to get it apart....THAT was a pink nightmare

[@FreddyFuFu]

TY for sharing your knowledge

[@smoluk1]

Way to go Scotty would be proud.....That starfleet degree payed off.

[@josephzielke8775]

Maybe the primary side of the output tranny is shorting on one side (the side that's red plating). The lower inductance would draw more current. Once the copper wire in the tranny heats up it'll expand and lock in the short until you turn-off the amp which colls/shrinks the copper. I would image playing live where the wire in the tranny could vibrate would create a scenario where the short is more likely. Could gingerly use a hair dryer to warm-up the tranny to try to engage the short.......also artifically introduce some vibration to the tranny.

[@abc123gpl]

i have had considered to buy an Mesa Boogie...… after watching four repair Videos of Mesa Boogies, that thought is gone .

[@VegasCyclingFreak]

14:15 The Seymour Duncan Convertible is actually easier to deal with - all the controls have little pins that the wires can disconnect from. I sure wouldn't want to have to pull that main PCB out of that Boogie... big P.I.T.A.

[@mikkjaggher4221]

What would cause a significant drop in power output? Wattage checked tubes and most caps. I'm thinking transformer has a short turn to turn

[@jimhart4158]

Brad: a helpful thing I found for step bits is backing them with a bit of wood. It slows them down and keeps them from binding in the sheet metal (caused by them trying to take too much at once). Gets a bit hot after a while though, so care is recommended. EDIT: Looking at the schematic, the resistance from the grid of the tube to ground exceeds the maximum rating of the EL84 (300k). This makes it possible with some tubes for grid-leak biasing to take place. I don't know if that is what was happening here, but it is important to note this spec when designing amplifiers.

[@soundknight]

Keep your amps simple gentlemen, keep em' simple.

[@johnthornburg4049]

Mesa does not usually do simple :-) Luckily their gear and their support is usually very solid. That amp has likely been working well since the early 90s - so what - 25 years old?You can expect problems in a 25 year old amp. I do enjoy working on the simpler vintage gear more, so I understand where you are coming from.

[@jimbaysinger1545]

Keep everything as simple as practical, for sure. For an amp, all I need on it is a volume knob. I control everything through my pedal board, anyway. My pedal board consists of a modeler with wah pedal, and a surge protector power bar for my amps and whatever else I'm using. I take the extra time to tweak my presets so the amp only has to be loud and clear. More shit means more shit can go wrong. I play my own music, anyway, so I can sound any damn way I please!

[@pb12661]

@@jimbaysinger1545 good luck selling an amp with only a volume knob to a guitar player.

[@jimh8422]

Is there any chance there was a piece of metal shaving causing a short somewhere some movement cased it to move

[@telecasteroil]

One thing learned, I’ll keep my old Fender Bassman never had a problem and easy to fix if it breaks.

[@lonegalaxy311]

hey. if i understand this right you have your bench in the basement. why not to put some noise isolation and just play a looper pedal into an amp and then probably come and check it from time to time to see if it fails?

[@jopestv1063]

I'm no amp tech, but even I know that mounting valves (tubes) directly to a PC board is JUST PLAIN STUPID. I'll keep my '65 Twin, thank you very much.

[@AEFXGTS]

Hey Brad, big fan of the channel but never comment. I also tech, repair and own a handful of vintage tube amps. I have seen this same scenario before in my early 70's Ampeg V4B. If the problem was in the bias power supply it would show up across all four tubes but since it is isolated to just one pair you know that it has to be somewhere just in that half. The coupling caps that feed the signal from each half of the phase inverter to each pair of output tubes have to block the DC 200V+ plate voltage from the inverter to keep it off the bias/signal feed. When those caps start to get leaky they will let some of that plate voltage thru and the bias will drift because of it. The thermal image shows those caps were working harder than usual too indicating that they are towards the end of their life. Cant blame ya for rebuilding all the other components however, its good insurance. The last thing you want is any amp coming back, especially for a 3rd time. But I am willing to bet that the root of this issue was due to one of those coupling caps failing. Always enjoy your videos!

[@robertcalkjr.8325]

Thanks Brad! Nice job! I have never worked on one of those amps before but I would go ahead and replace the diodes just to be on the safe side. Also, I would flip the amp around 180 and recheck my solder connections. A couple of times a solder joint that I made looked good in front of me but when I looked at it from a different angle it wasn't so good.

[@garywordsworth9302]

Burn it Burn it now, on a pire Or the Harvest will fail Only is screams will satisfy the divinities.

[@waltberger7885]

Is the amp working still ? or did ya get it back again ?

[@SiliconSet]

Great video series Brad, thanks for sharing.

[@DoRC]

Nice Fran tone!

[@Andrew-ry7iw]

It may not just be heat, but the actual vibrations from the speaker that is causing a cracked component or connection to develop an intermittent fault. What did your little component tester say about the condition of those hot running capacitors?

[@seansweeney3532]

yea, guys where I worked laughed when I bought a FLIR a while back, but that thing has saved me so much time, in tube amps, and especially big solid state monsters... and every day someone would borrow it! lol

[@dopplebear9755]

thanks for this! How can I get a hold of you to fix mine?

[@SiliconSet]

The copper trace at 3:00 looks dangerously close. Did it cause the failure I wonder.

[@quenchize]

Intermittent issues are the worst. In this situation you can try using a hair dryer (carefully) on the part of the board that you think might be failing when it gets hot. Then use freeze spray (which is more local) on each component to see if it recoveres.

[@muhammadsteinberg]

Looks like a bunch of cold solder joints...Did you do that?

[@davidhaddock5949]

what about some form of oscilation ? have you put an osciloscope on it in fault condition, looking for high frequency oscilation ?

[@robertphillips597]

It would seem that for the price of that amp, they would have mounted the sockets on the chassis?

[@TheGuitologist]

I agree.

[@jjswan1953]

i had just built a vibro champ from scratch and was having a problem with the bias running away . the problem was solve when i discovered a poor ground in the bias supply. re flowed the solder joint and it settled right down .

[@bryanstorm5268]

I own a Mesa DC3. Havent had an issues with it yet. Too bad the amp had gotten shut down during the red plating event. That would have been a great time to run test.

[@dwarden3]

Brad your gonna have to change your title to the amp exorcist, ha!

[@charlesb7831]

I believe I mentioned something on replacing/repairing that board on the first video lol. Just from past experience I can tell that board has been severely overheated and mounting the tube sockets to the chassis. We did the samething with my Carvin X50B after it caught fire because of that same crappy design of tube sockets on a pc board. It's such a terrible design on a good amp.

[@johnnyb3987]

Sometimes we don't get it right the first time. Keep the vids coming. I watch every one.

[@unclechuck5635]

Can you use a heat reader gun to take pics as you go to see if red spots heat up?

[@richardleerodgers5303]

the 47nF coupling cap from the phase inverter shown on your thermal imager must have been leaky transferring the plate B+ to the negative bias circuit in effect reducing the negative bias allowing one pair of EL84s to red plate. The reason it only happened on one side of the output tubes is you have the isolation from the bias voltage divider and grid blocking resistors in my opinion

[@markanderson350]

I agree about bias, maybe a current sensor like they did on TVs, they put a fuse on the cathodes of the sweep tubes. I would have headed straight for the coupling caps but I understand they are new.

[@runrabbitrun4342]

Last time i checked a bad connection doesn't cause Red plating. But what do i know. Can't wait for part 3

[@runrabbitrun4342]

This is fun. I love Friday nights. lmao

[@mars6433]

You fixed it TWICE ? YOU'RE THE MAN !!!

[@stephenmitchell7915]

Sort of piggy-backing on earlier comments. I used to work at NASA, although not an engineer. Our standard was to test it as you would fly it. Whenever we decided to save a little money and just test at the sub-assembly level but not test at the system level, in a real environment, we were nervous as heck. I can point to several examples where unexpected stuff happened after launch and we did not have the data to understand why. You may want to lock the reassembled amp in a room someplace and run some programmed music through it for 24 hours. After having some bad experiences, I would do this with any new stuff I would buy that was manufactured in China or made by Peavey. Lord, just the nasty smell from cheap paint, glue and particle board solvents being boiled off was amazing!

[@Andy_Yates]

The symptoms would make me think one of the coupling caps was on the edge of failing. When doing reading about the Blackface Bassmans, research told me that DC leakage through the power tube coupling caps could throw the bias out of wack. Short of elevating the whole bias circuit off the board, and making it point-to-point, I'm not sure what else can be done. It's less likely, but possible something found it's way under the main board and occasionally finds its way to shorting one side of the power tubes. I can't imagine the main board has become conductive like some Marshalls are known for. The other thought I had might be the resistors separating A and B on the B+ rail. Then I thought you'd see that in all 4 tubes. Is it possible the 470 ohm resistors on the 'bad' side would cause that? This is a tough one

[@johntempleton6368]

I hate working on MESA stuff almost as much as I hate working on Marshall TSL and DSL amps. Intermittent problems take a lot of time and are a dead loss for the tech. Customers blame the tech for not getting it done in one visit when they should be blaming the amp company for designing unserviceable equipment. I keep sweet grass and holy water on hand for intermittent stuff because sometimes it's as though you're battling a demon.

[@rangerdoc1029]

As a tech, a necessary skill is explaining to the customer that the repair process is just that.... A process. Sometimes you have no choice but to do process of elimination. Explain that to a customer in advance and you make everyone's life easier.

[@devinponder6072]

@@rangerdoc1029 Exactly

[@robertbull6895]

Surely it was the .047uF coupling cap allowing a positive voltage to intermittently leak through to the grids of the power tube, driving the tubes to red plating. Coupling caps do not get hot unless they are conducting current. The hot thermal image seemed to be coming from the body of the cap, not the leads or board.

[@pahaahv]

what's the song at 7:15

[@TheGuitologist]

I don't know! I was hoping someone could tell me. It's been on my computer since the MySpace days of 2006. I think it's by an Aussie chick named Mel. I have about 4-5 songs of hers and I love it. Stumbled on them for the first time in years the other day and have no idea who she is.

[@kevkeelan5106]

Sounds a lot like Angus and Julia stone, but I'm not sure.

[@salamisalesexpress]

Lemme look into it.

[@aroundthefur]

@@salamisalesexpress any luck?

[@salamisalesexpress]

@@aroundthefur tried most song lookup apps, nothing there. Reddit has yet to deliver either.

[@roncarter2188]

Brad maybe you can give me some input on a amp I'm having trouble with, it's a Silvertone 1483 and it's making some weird noises especially when I move my hands around on top of the power tubes. When i strum my guitar it has a bad distortion sound, not the good kind of distortion. I have checked all the connections and everything seems to be in order. I checked the output transformer and it's good. New filter caps installed and the power tubes are new, but not by me. Even checked and changed and tried different preamp tubes as well, no luck. Also when I turn the volume, tone and bass controls, weird noises can be heard low squeals and sounds like that. Any suggestions on what to look for ? Thanks for any help.

[@robertsmiczsmiczamplificat593]

Something i ran into a lot. Watch out for plate resistors (100k,220k) on 12AX7’s opening up under heat. They look fine, but under heat they open up. Some off them generate a crack that you just cant see. This happened a lot on Peavey circuit board tube amps as well as several boogies. I don’t think its the problem here, but its something that happens! A lot. Unless its a cracked or broken trace? I think you got it. You obviously didn’t need to build out the output board, but i agree it’s better off. I love boogie tone, but they suck to service.

[@johnthornburg4049]

when you have a pair of tubes redplate like that, save some time and flip the pair of tubes to see if the redplating follows the pair of tubes or stays in the same socket position. Saves time and sanity. Not saying that is your problem, but one tube can go bad and take the other one next to it with them. Even new tubes can die young. You may have already did this. But it lets you know quickly without digging into it (we all need that). Hah, I use the same harbor freight tools - I probably have multiple sets by now. I agree with all the stuff you did. Agree with the other guy that said to use your thermal to look at your new caps and see if looks cooler. Capacitors seldom get hot unless connected to something hot or something is wrong with it (or over powered - running 500v on a 450v cap, or whatever). But I am preaching to the choir. Did a nice job on the rebuild. Also, it happens very seldom but I have had damaged output transformer that had worked but was very imbalanced and caused issues. Also had conductive boards (marshall DSLs) - but I don't think so. Could check each side of the output transformer from side to center tap to see if very imbalanced. Also, I hope generally not to change too many values of resistors as I have concerns of a cumulative effect - and like to change one thing at a time as stated (but I can see the value of a shotgun repair and have been known to do that too). Your doing good work. I would think you have fixed it - at least I hope. I have worked on a lot of these and this is not typical, but they are now about 5 or 10 years older now, so may have more problems crop up due to age. But DC2, DC3 and DC5s are very reliable amps (and very similar except the output). I have owned multiple of these too - albeit - years ago now. Don't forget your chopstick test on the board to see if you have any cracked traces or solder joints.

[@johnthornburg4049]

Looks like my recommendations/theory close. Your doing the right stuff. Sometimes you get a repair that will kick your rear. You hit most of the common stuff. I'll watch part 4 just to make sure you got it. Good luck. Oh yeah, those that bash you for shot gunning don't realize that people pay you by the hour of work, and frequently you can swap a few things and fix the problem QUICKLY. The parts are not expensive, it is the repair. You try the easy and cheap stuff first. It fixes it 98% of the time.

[@joncurrier2269]

Did you try letting it get good and warm, then putting it on standby for a while, and back on again? The thermal cycle could reveal something.

[@MarshallSetUps]

I had a resistor issue with an 01' 100 Watt Dual Rectifier. Fixed it, couldn't play it loud enough, and sold it. Can I buy a sticker?

[@snakeeyes3733]

How the heck would you be able to check for a cracked trace under the board while it's powered up?

[@Robert-xn3jb]

Good God! I hate working on Mesa. I had a Studio 22 on my bench 3 times. The circuit board was charred from heat and randomly creating carbon paths. I love my Mesa D800 bass head but would never own their earlier tube gear!

[@JazzzRockFuzion]

I've owned a '92 Studio .22+ since March; had it out on a handful of gigs & a bunch of rehearsals/recording sessions since early June. Zero problems. Maybe I'm lucky? I know heat is a serious issue with these Studio/Caliber amps, so I always give the amp plenty of breathing room and turn it *completely off* if I'm taking a break longer than 5 min. I suspect that folks leave these little Boogies sitting 'on' for long stretches, pressed flush against the wall, or what-have-you....leading to frying/glitching circuit boards.

[@skynet3d]

The kings of charred pcbs are the Fender Hot Rod style amps, Blues Jr and the like. Bias is always set ridiculously high, tubes upside down and a PCB are a recipe for disaster.

[@dankress8228]

JazzzRockFusion-your Studio 22 that you got in March probably has already been serviced. I have one that was built in 1986 and I did a whole cap job myself and also found a couple resistors that were so burnt out that they were cracked in half! Brad’s videos saved me a ton of money because the local Mesa dealer wanted $200 to fix it, and I spent a grand total of $40 to do it myself! Since then, I took it to one gig and a few jam nights and she stands up well to all my friend’s hi dollar new-fangled equipment!

[@photopicker]

@@dankress8228 $200 to repair the amp is a song. Great that you knew how to fix it but if you ran that shop would you feel comfortable charging a customer $40 for your work?

[@dankress8228]

photopicker The local Mesa dealer first wanted $80 just for me to walk in the door with that amp! Still gotta say I’m way ahead since the new Mesa Fillmore series that I like costs $1600. Even if I did end up paying them to do the job I’d still be ahead.

[@rickmckee8270]

use sum flux remover on your solder joints hit the circut board with some canned air to cool sections circut board of the to check for the thermal effects. and see if you can repeat the failure. and when you drill out the chassis clanp it to the bench you can also put sum tape around the dia of the bit so you do not drill the chassis at the wrong size. the lighted magnifier are helpful at finding issues with circut traces quickly hope you find these tips helpful.