#1
The volume and sound on my super reverb is inconsistent. It will go from loud to quiet while I'm playing, and if I try to use vibrato/reverb I get a bad crackling sound. I bought the amp used, and the guy before me said he had it for 3 years, but never changed any tubes, but rarely played it, and it's been in my possession for about 8 months. I'm assuming I need new tubes. however, I've never bought tubes before, and I don't really know where to start.

Tube (valve) complement:
4 X 12AX7,
2 X 12AT7,
2 X 6L6,
1 X 5AR4/GZ34 RectifierTube

Should I just replace all of them and get any brand of tube, or replace just single ones, or something. Is this something I can do myself, or should i bring it in to a shop to get fixed? Could it be possible that the problem isn't my tubes?
#2
I had/have a simular problem. Turns out the pots (volume &tone knobs) were dirty (any movement of the knobs caused vol to drop/crackle/sound terrible in general). Got them cleaned professionally and it dramatically improved the problem, however the tubes were a bit worn out and also need to be replaced.

Im sure someone with more experience will correct me but.. Power tube are usually replaced in matched pairs or you have to bias them. The pre tubes can be changed one by one by if replaceing with the same tube, if putting different ypes in I think you are supposed to change the lot.

Good luck
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#4
Quote by countervail
The volume and sound on my super reverb is inconsistent. It will go from loud to quiet while I'm playing, and if I try to use vibrato/reverb I get a bad crackling sound.


that could be a number of things. sounds like it is most likely 2 seperate problems actually.

when power tubes go bad they can do a 'volume swell' kinda thing with a kinda 'choking' / static sounds (like almost when you put the amp on standby).

when the vibrato/reverb channels don't work, it could be just a dead preamp tube.

Quote by countervail
I bought the amp used, and the guy before me said he had it for 3 years, but never changed any tubes, but rarely played it, and it's been in my possession for about 8 months. I'm assuming I need new tubes. however, I've never bought tubes before, and I don't really know where to start.


i'd check your preamp tubes first. mainly cuz you can do this easily and pretty cheap. so, before you buy a whole new tube set just buy a 12AX7 (or two, sometimes you can get a dud and it's nice to have two cuz it's rare you get two duds). then follow this procedure:

1) remove respective preamp tube

2) replace with your newly acquired tube

3) test amp to check for improvement in sound

4) take the new tube back out after testing it and put the old tube back in (assuming the new tube didn't fix the problem, else keep the new tube in there).

5) return to step 1 and test the next respective tube.


i prefer to start replacing tubes from one side of the amp (generally the left side) and work my way over to the other side. one or two 12AX7's will be fine for your 'testing purposes (don't worry about 12at7 and 12ax7 compatibility, the tubes are interchangeable enough for your trouble shooting purposes).

you can also get a new rectifier tube (the 5ar4 style tube) and test that as well. unfortunately the power tubes will be a bit tricky as they will require some biasing for proper operation. it is best to take it to a amp tech for this process.

Quote by countervail
should i bring it in to a shop to get fixed? Could it be possible that the problem isn't my tubes?


i would bring it into a shop and have a tech do a once over on it, that is what i usually do with vintage amps. it could be something besides tubes, could be something like a burnt resistor or blown cap (the caps they used back then didn't last too long, and generally need replacing after 15 to 20 years. a tech will be able to test you caps and tubes and tell you what needs replacing.
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Last edited by gumbilicious at Nov 25, 2011,