Question:
Hey all,
This past weekend, my amp has been giving me troubles. It's a Mesa/Boogie Studio .22 1x12, powered by 2 EL-84s. I'll start it up, let it warm up for a minute or two, and then take it off standby and begin playing. After a variable (but short, 5 minutes or less) amount of time, the amp begins "crackling" and then the volume level just drops down to a tiny fraction of what it should be - the amp just barely "whispers." If I place the amp back on "standby" and then back out of "standby" again, I buy another amount (shorter than the first) of playing time before the same thing happens.
Any ideas which component(s) may be causing this problem???
Nate
Answer:
I'm guessing it's the tubes...
Answer:
Might be tubes...though it sounds like my amp problems, which were bad/leaky filter caps. Or depending on how the amp is put together, maybe a bad/cold solder joint that finally decided to give out.
I'd try to get the tube part out of the question...check the preamp tubes (sure you know how to tap them and listen for any noise)...if you've got another set of power amp tubes try swaping them out.
The caps are a little more difficult, most meters don't have a capatacince scale...but you can usually tell just by looking. Look around the ends and see if you can see anything "leaking" out. Or if there are any buldges or if there is any discoloration on the caps.
Solder joints...hum...don't know what to say other than give it a good visual look, maybe the "careful poke" method...
Answer:
i had a problem just like this on my old tube amp... i always thought it was the tubes, i was about to replace them when i found out what the real problem was. it turned out to be the fuse holder.... the connections went bad, and when i wiggled it, the amp would come back alive. it might not necessarily be the fuse holder, if you have one, but it could be something similar
Answer:
my peavey XXX (just bought it yesterday, had it less than 24 hours when this problem occured) has shut off completley. It won't play anything. It started with the fizziling on and off, then it just shut down completley. It will get power, turn on, change channels, and all that, but it just won't work. How could this have happened. It's brand new!!!!!!!!!!!!!!
One thing that occured to me was that it was the display model in the store. I wonder if maybe something got bumped around then? I have no idea, but this is extremely aggrovating.............
Answer:
Swapping tubes out would be a good place to start, but kinda pricey if you don't have spares. Aside from that I would try tapping on the tubes before it goes out, see if that does anything like the crackling sound. It might sound stupid, but another thing I would do is play thru the amp, when it messes up, I would try bumping and thumping it to see if it comes back. If so, I would suspect a connection, bad solder joint, although it could be an internal fuse for a specific thing if it has any. The heat up thing could be just about anything - bad connection, broken solder joint, tube, other component... With the heat up/problem cycle being pretty consistent, I would tend to suspect a component - tube or otherwise first.
Answer:
Well, I think I've got 'er back in fine operating condition. I took the chassis out of the cabinet, drained off the filter caps carefully (my multimeter indicated that each had stored up about 21 volts of potential), and then proceeded to do an all-around check-up and cleaning. I checked all the solder connections I could get to, cleaned the tube sockets (which I think may have actually been the problem), checked the major resistors (as indicated in the schematic) to make sure they were close to their prescribed values, and checked for ground continuity at several different points. Slapped 'er back together and she's been singing ever since...just thought I'd give an update on the situation.
nate