Eurotubes Generic Bias Video

[@thatampguy]

Eddie!! Dude I just happened into this. Thank you for being such a great guy. You’ve helped my biz so much through the years.

[@joeemenaker]

What a great vid. This guy is helpful, patient, unpretentious, and methodical. Doesn’t come across like he’s trying to sell you something, just sharing his expertise in servicing tube amps. Oh, and he can probably curl about 80 with either arm.

[@ChadVanHalen5150]

I watch this video every time before biasing... Super super useful, and definitely makes Eurotubes a company worth supporting whenever I can

[@tadpui]

I had to let you guys know that this video is a gift to humanity. I have an '86 JCM800 2204s, and this video was my main guide to biasing it. Bought the Pro One and it works like a charm. Thank you for providing this info!

[@rickmilam413]

That was the single most helpful video on this that I've seen. Thanks.

[@ShrednecktheRedneck]

Beautiful, I learned everything I need to about changing my tubes thank you

[@PapaBoo]

this is the best and only video to tie it all together, including the calculation and the different meters which may or may NOT easily give you both the plate voltage and the required tube setting based on the calculation you need to make.

[@woolyfuzzy]

So clear and concise. Thank you so much for putting the video together. I do have one question though... do I need to measure both power tubes if I have a matched set? I only have one of the pro bias meter tools.

[@zhou_sei]

what i do on my princeton is measure each separately (i have the basic bias probe) and just make sure neither one is biased too high but both are high enough for rock n roll. disclaimer: i'm a newb.

[@artysanmobile]

The special tool plugged between the socket and power tube shows current directly and is super handy. The tool uses a small reference resistor across which a DC voltage measurement is translated to current by the meter. It really is a great solution. That convenience comes at a price, though, and multiple versions will be needed for different amps. There is another solution. 1. Use secure clip-style leads for all measurements on your meter. The power tube plate is very simple to locate. Clip the MINUS lead there, assuring it is very secure. The output transformer’s center tap takes a bit of effort. The easiest place to access it is the + terminal(s) of the largest filter cap(s), the chassis mounted ones on a Marshall. Clip the PLUS lead there. WITH THE AMP OFF, set the meter to resistance and note the value ACCURATELY as R. Expect a value in the range of 30-50 ohms. 2. Change the meter to DC volts without touching the clipped-on probes. Power and warm the amp. Note the voltage accurately as V. (for example 1.94Vdc) Keep in mind though that each probe is tied to a point with 400-ish volts so be safe and secure. Now, for some math. 3. With V and R noted accurately, (V / R) = the bias current is read in Amperes, such as 0.040 for 40mA bias. Adjusting the bias pot will change the small DC Voltage. A higher voltage = higher bias but the equation needs to be repeated for every change. ***There is no direct readout for current. I write a list of voltages with their resulting number of mA in the equation and put this info on a piece of paper tape stuck to the inside of the chassis. It becomes second nature.

[@RobAndKim444]

You're a natural teacher, thank you 👍

[@frankdelima8778]

Great video. Great step-by-step! Thanks so much!

[@BillMcGirr]

Really well done video.Informative and thorough. Thank you...You've earned another customer for your product.👍

[@mookytc]

Thank you for this video and information. Have a ET Pro One to dial my amps in when changing tubes.

[@AnonContributor]

Such a great vid. Come back to it a few times...Good work Eddie!!

[@roadglider6001]

Great video, very well explained! I have a question about the mA reading on my EL34 tubes. One tube reads 45 mA with a plate voltage of 496, and the other reads 35mA with plate voltage of 498. Is that normal for the tubes to have that much of a difference in current mA? They are not a matched set of tubes and I am using the Pro One Bias probe. Any advice would be welcome.

[@jeremycusick5399]

It's the tubes not being a matched set that's causing the issue. You can either get a matched set, or set the bias to a middle of the road setting that'll keep both tubes happy.

[@christosfragias592]

It would have been nice to hear the amp before and after rebiasing and retubing.

[@davebird534]

Awesome video man email learning this process a lot easier! Thank you

[@mikemaj8467]

Isn't it advantageous to have a bias probe for each tube? If so would you use a bias meter for each power tube, or do one at a time and power amp off before disconnecting probe from meter and reconnect to other bias probe,

[@andrewwheelerguitar]

This all works for 6L6 power tubes and 5AR rectifier in a black panel vintage fender?

[@edwardebel1847]

Just a safety note: the reason to only work with one hand at a time is so that if you get a shock, it doesn't pass from one hand to the other and go through the heart region. This can cause defibrillation and all that comes with it... A current passing through one hand and exiting a foot is much less likely to be fatal...

[@100amps]

I've been using a Pro One (octal) bias probe now for a couple years and I love it. If you're working on more than 1 or 2 amps then I highly recommend grabbing one of these. I has been completely reliable. My only beef (if you're listing ET), is the font labeling on the meters (the little plastic tape labels). I'm getting older and couldn't read that font without my glasses. I relabeled it with a 'normal' font and it's perfect. Not a big deal really, but ...

[@scruffy2365]

Great dudes, very helpful, my amps like new again, that marshall tone

[@1thess523]

Was there a snare drum in the room?

[@f.duranleau4416]

Hi. Would it be a good idea to turn the bias trim pot all the way down before turning the amp on so the new power tubes won't have a voltage peak that could damage them? Thank you! Great video!

[@davidroberts2595]

Good question I hope they could answer

[@artysanmobile]

Clean the glass of any tube or lamp you replace with your fingers. So easy.

[@adamhart3378]

I have a question. Is the plate current the bias setting? That's what it looks like in this video. I have a 100 watt Marshall amp and my plate current is 60. Is that my bias setting? My plate voltage is 485.

[@marcos061059]

Outstanding vid. Thanks for the great information!

[@sideparting6845]

Extremely helpful video, thank you.

[@jamesfindice2871]

Awesome video! Do you need two probes or is it enough to use Only one?

[@PabloRomero1991]

Awesome video I just purchased a set of gain tubes for my Jet City JCA20H head and a pro-one probé but how many watts is the output rating of a JJ EL84? Thanks!

[@JohnLee-mq4hk]

Some techs say that using tubes that aren't perfectly matched are better for harmonics, what do you think?

[@buddybeetle]

Excellent instruction. Many thanks !

[@64mung]

Hello..I just used my new Pro One for the fist time on my 79 Fender Twin (135 watts..6L6GC tubes) My plate voltage is 509 VDC. After the math (25W divided by 509VDC = .0491 x .7 =.034) my plate current should be set at 34MA, but my bias pot will only go to 26MA. Have you ever had this problem before? Any suggestions?

[@fostexfan160]

Great video. Very informative

[@MosheAlvarez]

Jcmslash: You're welcome, sir

[@ako1234ako]

hey! just recently got my peavey triple x 2 with stock ruby el34's in it. im thinking just in case the tubes are going to be worn out, how should i bias the new tubes? im thinking of putting 6l6gc in it but im afraid if it will lessen the gain(like what i've read from an article by premier guitar) or again el34s. im planning to buy the pro one and my question is(in case i have a pro one) should i try each tube with the pro one, or just one tube?? thank you! im really new to tube amps. and your reply will be very very very very much appreciated. greetings from the philippines! thank you.

[@SturmAKS74U]

Have a Bruce Zinky gem in the Fender Prosonic head - what’s the safe range in plate voltage? I didn’t see it on the site under the bias notes.

[@lousekoya1803]

Awesome teacher !!!............Thank's !!

[@francoispoirier1557]

Hi, great video, I have 2 questions, do you have to set all knobs to 0? Also does the bias change by itself with time? Lets say 2 years after? Thanks.

[@brianm9282]

The bias doesn't change, the tubes do.

[@Christyan17]

How many pro1’s will i need for a 100watt amp? 4?

[@pbf98]

I notice that you are using 2 probes, is it necessary to check the plate current mA, and plate voltage on all tubes? If so do you wait for all to cool down and switch it up? And finally what if there is a discrepancy for plate current between tubes?

[@riffsnreviews]

Not necessary but useful. Anything up to about 20% difference isn't a major problem and can actually sound nice, brings out harmonics. But set the bias on the hottest tub reading. but it's not really god if you have for example 4 tubes and 2 that are matched the same, 1 at -20% and the other at +20% that's too much of a mismatch. In reality everything matched and balanced in a guitar amp just takes away from the tone... (preamp balanced paired tubes are a joke lol).

[@ampegloud]

How long are you supposed to let the app warm up before you take a bias reading?

[@electropentatonic]

The first thing we're gonna do is HULK SMASH

[@tooclosetovomit6970]

Hey mate. Thanks for the video. I'm the kind of person that would stop and bring the amp into the shop, but the coronavirus makes that impossible. I have an Ampeg B15 S, a power tube went out, and I have some NOS RCAs to replace it. Wondering if you by chance have that or similar amp around because I'm looking for a step-by-step so I don't electrocute myself, but no one has made instructions for that one yet. Cheers.

[@billwilliams6338]

EUROTUBESINCE, How do you bias the power tubes compression point when the tubes start compressing? you mostly use bias current at 30mA per power tube but how do you when the tubes are compressing?

[@brianm9282]

You bias the power tubes to what the schematic says.

[@markolivares6943]

Do you need a probe for all power tubes ? I was informed you only needed one to bias all of them since they are all running the current

[@montag4516]

As long as the tubes are matched/rated within reason to each other then a single probe should do the trick.

[@luissalva7890]

excellent video...thanks!

[@jimmyd5037]

So if you have 4 power tubes do you just repeat the process with the same settings as the first 2 power tubes?

[@jimmyd5037]

Thanks for the info!

[@danyjr]

Do I still need 2 metres, one on each tube if I have a matching pair of tubes?

[@montag4516]

Just one meter/probe is fine. That goes along with the point and additional benefit of having matched tubes.

[@JCMSlash]

Hey Eddie Is it the same way with a marshall jubilee 100watt ? messuring the plate voltage ?

[@MosheAlvarez]

+JCMSLASH - NoahThawco Yes it is. That's pretty much the way to check ALL amp's plate voltage

[@JCMSlash]

+Moshe Alvarez Thanks man

[@MosheAlvarez]

You're welcome, sir!

[@tommyholt3627]

isn't the 2nd tube probe and meter redundant? can't this be tested with one probe only?

[@riffsnreviews]

it can be done with only one, he used the second one to demonstrate their cheaper product, but there is a practical use for having the cheaper second one in at the same time it will tell you how matched the 2 tubes, and if you have 4 tubes it's also interesting to plug the 2 sockets into the 2 other tubes afterwards to take the readings. Though perfect tube matching isn't necessarily a good thing on guitar amps imo, not like it is in hi-fi, coz you're not looking for a sterile neutral tone. A 15ish % difference between tubes can bring out nice harmonics and is not dangerous for the tubes, as long as you set the bias on the hottest tube, take it up to 75/80% even you'll only lose 10/15% lifespan on that tube.

[@kenthompson43]

AWESOME...Thank you.

[@jonathonwerner5968]

I just prop the chassis in the headshell it came out of. I'd rather buy a set of EMG's or new tubes instead of that head stand for a chassis. But the tip on some books is valid!

[@brianm9282]

I use two, one dollar yoga blocks from walmart.

[@jaredheld2672]

Where can I buy this? Everyone seems to be out of stock for some time.

[@brianm9282]

You can easily make your own for pennies compared to what sellers charge.

[@johannesschuster256]

Plug the tube, do not rape it :) Treat her smoothly and slow around an think of a lovers night. But the vid is a real nice and good job. And thanks for the inspiration with that workframe - must be very helpful.

[@JamesLee-sq2cx]

Thanks!

[@paulproductions9213]

BUGERA AND HUGHES & KETTNER HAVE AUTO BIASING, AND IN MY OPINION ALL AMPS SHOULD COME LIKE THAT, FROM NOW OWN I WILL GET AMPS THAT DO THEIR BIASING BY THEMSELVES.

[@PeterDad60]

Yea so then you have no control over the bias. You can't set it cool and you can't set it hot to taste. You let the Chinese control your taste in tone. Good for you. Me? I'm not as lazy as you and I do prefer to control my tone/break up/clean through the bias of my amps.

[@brunoluznunes]

ohh! Looking to the guts of that amp it could be 1/3 smaller! Easier to carry around...but no...big is better, that's what she says...

[@PeterDad60]

The other side has two huge Transformers mounted and they need to be not too close to the tubes. So no, a smaller chassis is not a good thing here. Also the chassy needs to be secured into the wooden box and that box needs to fit on top of the speaker cabs. Lastly the chassy is where the controls are mounted. You don't want the knobs too close together.

[@infectionsman]

The thing is, marshall designed these amps to look cool. So they removed the arched part at the sides of the front panel that the older amps (87x 1959 etc) had that covers the sides of the chassi. So obviously you cant use the smaller 50w chassis with this design. This is why this amp uses a full 100w chassi even though it is a 50w model.

[@LevRage]

Cradles are simple to build.

[@josephrileyosullivan]

You're committing the cardinal sin of touching your tubes! Doesn't the oil from your fingerprint change the way heat dissipates?

[@brianm9282]

No, tubes were used during World War 2 and exposed to the worst conditions, I doubt anyone changing tubes used white glove treatment.

[@64mung]

Great video...thanks!