Finding A Bad Tube In A Tube Amplifier

getting your dirty hands on a tube won't damage them in any way... This is a myth Still a good video mate!

Used this tapping method on my 93 fender blues deville. After hearing a loss in amp output and a weak dirty channel, i found a bad 12ax7 closest to the power tubes. Saw this vid and figured id try it before i get beat over the head by a tech.. and honestly with the volume up, a extreme light tap will do, its very audible. Total cost $14 Thanks for the video

My amp has 12 tubes. I tried this and it worked. The one bad tube made a loud noise through the speaker when I tapped it. Thanks Renato.

Good demo of some bad tubes. Thanks for posting your video.

Awesome video thankyou so much! Just did it tonight on my marshall and was actually relieved to find one bad preamp tube. Reassuring that i wasnt going crazy!

Credibility lost when I heard oils from hands can cause tubes to fail 😂😂😂

Damn so many components in this! Amazing.

Man you helped me chase down a problem on my Orange Rockerverb that had been bugging me literally for years... thanks so much!

That's a nice twin the first two tubes are for each Channel unlike most tweed amps this amps Channels are not sharing the same preamp valve. Usually each channel uses one side of the valve on the first one on the right. It's placed on the right farthest away from the power transformer for a reason beacause of 60 cycle hum. The next two tubes are aloud to be microphonic because they do a different function in the amp. So an easy fix is moving them around. Just because a tube is microphonic. Doesn't mean it's bad it actually give the amp more lively sound as long as it's not rattling or ringing. Also log plate 12ax7's tend to be more microphonic than short plate ones. Ps - don't bang on your tubes or move your amp around when there on or hot that is how they become microphonic and rattle. Get tube rings they help!

Good video, thanks, very helpful. I've got trouble with my Marshall TSL, no sound at all, and a burn smell...the 2 fuses look OK...I changed all tubes 4 months ago, everything was perfect until the last time I used the Amp...I don't know...do you have an idea ? thanks for your help...

with every knob turned up i would say those tubes are pretty quite ! and dont worry about touching them with your bare hands it has no effect on them, it's true ! cool old amp man !!

I have a laney cub 10 and the gain knob doesnt work anymore but I cant hear anything even if I put the volume knob at 10. but if I crank up both gain and volume knob, I hear the clean sound. but considering that I cranked them both to 10, it still sounds quieter than before. I still hear alot of distortion when using my boss overdrive/distortion stompbox though like nothing changed.. so weird..

..just putting out there. I have found most of the new fender amps develope that microphonic ring. Sometimes just replacing the noisey ones alone does it but I have found that the valve bases are sometimes not fitted properly with enough solder.

Christopher Walken as recording Producer Bruce Dickenson walks in your studio.."honestly, it was sounding good, but I could have used more chopstick"..."Renato, explore the cabinet space".

My Peavey amp head is making aloud Hum & thats with nothing plugged into the amp. And when i do plug my guitar in I have to CRANK the volumes and its barely louder than speaking volume. Any guess if its a tube or not?

Hello. Thanks for the video. I recently bought a second hand bugera333xl (not the infinium version) and i found out two of the pream tubes are microphonic. Here in my country replacement tubes are either hard to find and expensive. I need to know how dangerous is operating the amp with microphonic tubes? Shoud i wait until i can replace them before using the amp? Besides that, there are 3 diferent tube references 12AX7A, 12AX7B and 12AX7C what is the difference between the tree tubes? any information you can give me would be most apreciated. tahnks in advance.

If you're changing preamp tubes again after one year, something is not right with that amp. If it sounds harsh, maybe you have a 12AX7 in a socket that you should really have a 12AT7/AU7 in. It's a common mistake. They look the same, fit the same socket, and the amp still works. But a 12AX7 has a lot more gain. The driver tube and reverb driver, are often a 12AT7 or 12AU7. But I'd get the amp looked at, rather than keep destroying tubes, if there's a problem. Maybe you have plate and grid resistors that are way off value and your B+ is too high. It's also possible you bought trash tubes or got gypped. If you work in a place that sells tubes, you probably play guitar. When your own tubes need replacing, it's all too easy to swap them out with good ones from work. just pop your bad tubes in the box and put the box back on the shelf. I'm sure it happens. If tubes are going bad in one year, something ain't right.

Love the amp. Either it is an old tweed that has been heavily modded or it is an reissue ..... old Fender tweeds do not have ceramic tube sockets. I have an old Supro s6650 with its original tubes that I haven't played or fired up for over 25 years. As soon as I can I will have it checked and serviced along with a three prong upgrade. I wish I had ceramic sockets. $$$$$ If tubes need to be changed every year I would suggest looking at the biasing. I would also suggest playing it as needed and have a practice amp from Goodwill for home use.

How much power does that amp put out ,it seems to be a very well put together amp ,clean ,how about a good vintage tube tester .

RENATO PASQUALINI, the B+ voltage is at 450vdc and if you increase it to 600vdc will this increase the AC ripple voltage and output wattage of the amplifier?