How do you know when to change tubes

[Andrew07]

At moderate volumes, I'm starting to get some tube rattling when playing the A string. I got the amp second hand and the guy said he had just put in new El34's, but hey who knows if he was telling the truth.

 

[Wolfeman]

Tubes can be brand new and still be bad.... I'd do the tap check to find out if it's a preamp tube. Could just be one that is slightly microphonic. If it were the power tubes going, you would get random drop outs of output at random times....

 

[Loren Littlejohn]

I am so lucky to have a store nearby that has a tube tester unit. They repair and restore old radios and amps.

 

[deanbailey]

Sorry about hijacking:
I wanted to ask about this as well.. Andrew07 mentioned tube rattling, my Rev1 has a weird "chiiing" sound coming through the cab when it gets played while resting on top of my resonating cab during some 'chuggin'. But when it's in the control room and cab in the booth it's fine.
This is actually my first tube amp so I'm not sure if its a tube problem?
Oh and the head is about a few months old and I'm still using the stock tubes.

 

[deanbailey]

Anyone?
@ Wolfman: How do i do a "tap check" without damaging anything, and what do i look for?

 

[Torniojaws]

Tap check:

- Put your amp fully on, don't connect an instrument
- Tap each tube lightly to the side with a pencil and listen to the cabinet

If you hear just a small "clunk" or such small sound, the tube is fine. If you hear a bell-like long chime sound, the tube has gone microphonic. You should replace the tube.

Here's a nice checklist/debug list for various common amp problems:

http://www.geofex.com/ampdbug/ampdebug.htm

 

[JonWormwood]

Tap check:

- Put your amp on, and on standby (no sound when you play)
- Tap each tube lightly to the side with a pencil and listen to the cabinet

If you hear just a small "clunk" or such small sound, the tube is fine. If you hear a bell-like long chime sound, the tube has gone microphonic. You should replace the tube.

Forgot to mention eraser, pencil eraser.



I will just anything to tap tubes, picks, finger nail, etc.

 

[deanbailey]

Tap check:

- Put your amp on, and on standby (no sound when you play)
- Tap each tube lightly to the side with a pencil and listen to the cabinet

If you hear just a small "clunk" or such small sound, the tube is fine. If you hear a bell-like long chime sound, the tube has gone microphonic. You should replace the tube.

Aah Thanks a lot, I guess mine needs replacing.

 

[Wolfeman]

Yeah I usually use chop sticks, they never do me any good at the Japanese Steakhouse when I go, so I bring them home for poking around in my amps

 

[Deus.exe]

Yeah I usually use chop sticks, they never do me any good at the Japanese Steakhouse when I go, so I bring them home for poking around in my amps

I use them for air drumming at work