How to fix Peavey Classic 30 Tube Guitar amp 6BQ5 red plate condition D-Lab 

Straight to the point. Good job Terry.

As DLAB always says..... always look for the obvious stuff first before you dig in and start ripping things apart. Nice job as always Terry.

I've had very good luck with TungSol reissue tubes. Interestingly enough though, I took a working amp in for a restore job, and my tester failed two of the pre-amp 12AX7's(tung sol). I don't know why, but they sounded fine, and showed no evidence of issue. One of my rules is, if the tubes don't test as good as new, I replace them if the amp is being sold.

Just received a Classic 30 combo that had a bad hum. That was a bad power supply cap. Upon testing the amp the second to the right tube red plated and was due to loss of bias voltage. All tubes tested good. Pushing on it fixed it. It turned out to be a bad tube socket. Something must have happened to this amp as all the power tube pins were bent.

I like the good basic technique you have i nice test gear Philips fluke and hp but I lust for your tube tester I like to develop new circuits and need a good Gm reading but I use all of three types I have seven different tube testers including Simpson Precession electronics and on but to have one that holds calibration would be soooo nice last time I checked they were about $2,000.00 are they still ?

You talked about bias, did you set that when replacing those power tubes? If you did could you do a vid on that, I have a 3-12ax7, 4-el84 amp and wondering how to do it. Also should you use matched power tubes? Can you mix pairs with other brands? Thanks for the great video's, you Rock!

EL84/6BQ5 has a max palte voltage of 300V, whereas amp manufacturers insist on running them at 350-400V to get the last few watts out of them, hence the failures. Operated at the rated plate voltage they're great, reliable valves.

I ran a another resistor X the divider n ran it colder, still sounded GREAT, Man they run HOT stock!

Thanks for the video & input.

Peavey Classic 30 amps run hot ask anyone. 350- 400 plate voltages. This is very true. My 1995 Classic 30 plate voltage is maxed out. All these Classic 30 watt amps run bone hot with no fan. Just touch it. The preamp gain was Soldano, almost Boogie Tri-axis meltdown distortion. cool. But, It made a lot of racket, micro phonic preamp tubes too. I turned it into head with a hardcore baffle and high output fan. I upgraded the tubes also. Now its under control and sounds great. I also have another Classic 30 head (2008) which runs half as hot with no fan. They knocked back the voltage a bit. I use them in stereo 60 watts A, B and A+B, its fantastic sound especially live.

When you say it damages the amp - in what way? You didn't show any check of internal components. Any idea how these are failing? The only thing I can think of that would cause high plate current is either gassy or control grid short.

Arent there usually sacrificial resistors to burn open when a power tube goes beserk? Love your channel btw. Well done Sir.

Not a fan of 6BQ5's either. to top things off, Fender runs them at 40mA in the blues Jr. Talk about pushing the envelope! That's why I've come across many charcoal broiled circus boards among my repairs.

Nice job, Terry. Does mounting the tubes in the "upside down" configuration have any noticeable effect on tube life?

I love your tube checker - I bet it is very expensive?

I build and repair lots of amps with EL84's and do not see what your saying about failing and taking out the amp's circuit. Tubes of all brands are just plain not as good as NOS and that is a problem with preamp, power tubes and rectifiers.

My classic 50 410 with a fixed bias does this after I swapped the 12ax7s with 5751 reissues only on full volume

I have no problems with NOS 6BQ5/EL84.

Great job, man!

Do you test your guitar amps with a guitar after you fix the problem?

I was interested in your results from the Amplitrex. The readings showed a good tube although you rejected it . Is the Amplitrex then a waste of time ??

I have always been a big fan of 6V6 they are American design and are more rugged with a similar capacitance. I love my 6L6 for typical higher power. 6BQ5 are ok but the are pushed harder for sure less cooling for heat 🔥 dissipation!

Tube Amp Theater! Hoooray!

EL84M’s are your friend. They are more rugged. Not a fan of EL84’s in guitar amps but love them in audio amps. Robert

Could convert to 6cm6. Sounds great

Nice!!!

I think of EL84s as the Beatles' tubes. I don't want an amp with them though.

Like the T-shirt -- N8CA

This is what I would call a lucky repair. I've had a classic 50 here with me. Not a customers. And I have troubleshooted every aspect of this amp. I've scratched my head for months and have been unable to figure out the issue. The amp was given to me as a basket case. And they were right. I have replaced tubes, I've replaced resistors, checked OT, it's been recapped, etc. While the tubes have now stopped redplating, all four use to. It still sounds horrible. Like the day it came to me. Low volume, distorted and lifeless. It sounds like a 1W amp played through a telephone.

And to think Hartley ran them even hotter in th classic 50! Ran those plates up 390 plus volts! 🤔 Put a big old fan in there!

I had this problem with my soldano atomic 16, it works very well with current production tubes, but red plates with no’sSylvania tubes after many hours on google I read an article saying that modern production el84 tubes have pin 1 and pin 2 internally jumpered, while he Sylvania 6bq5 tubes were not, I’ve since cut pin 1 on the Sylvania no’s tubes and the problem goes away

Red in the face? Try to replace!....LOL