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problem with my amp, please help me!

N

nickbear

Jun 12, 2007
593
6
surrey, uk
www.myspace.com
#1
hello talkbassers

i really dont like making threads without it being absolutly neccesary but i feel like i am not the point where i have to!

ok my problem is as follows:

I own a 2004 ampeg svt3pro head, I have used this head on average 3 days a week and it has been kept in a gator rack case, it is in great condition.

A couple of months ago it starting malfunction, it would dip in volume and the peak/mute light would flash on while this is happening ( not all of the time though).. this problem did not happen that often but enough for it to cause me concern.

I took the head to the shop i got it from .. They tested it and tested it and they couldnt get it to mess up.. but they wouldnt look in it! so I took it to another shop that has a decent amp tech that has fixed stuff for me before and I know he does a good job.

This guy opened it up and tested it exentsively and could not find anything wrong with it, he said the groove tubes that were in there were in great condition and showed no sign of needing replacing, their were no dry solders or loose connections either.. He said everything looked fine except it was a bit dusty in there so he gave it a good clean.

I got the head back (6 october) and it doesnt seem to have the problem anymore! Ive used it to practise and gig and it seems fine, hurrah!

Then at band practise on tuesday and today the amp starts to mess up like it used to but only more frequently, I make sure its not anything to do with my leads, pedals, cab, power lead, bass just in case but it still seems to make the problem.

I really dont know what it could be or what to do, i really like the sound of this head and i really dont want to buy a new head but i feel i might have to.

Does anyone have any suggestions on what it could be?

or

Does anyone know any similar heads that i can replace it with and not drastically change my tone?!

sorry for the long post, I have searched the forum for any sort of answer but i could not find anything

Nick
 
#2
This might be a possibility: As far as tubes go, our guitar player had the exact same thing happen as you. The techie said all was good, but what was happening , (we found out later) was in the shop, they only tested the tubes for about 10-15 mins. As the tubes got warmer , say, after 30-45 mins,(at practice) they started to malfunction. I guess a sign of "on their way out", but not out yet. The tech said it couldnt happen, but our guitar player changed out all 4 of his tubes, and never had the problem again. Hope this helps.
 
#4
ok thanks guys, shouldnt preamp tubes last a lot longer than 3 years?

which tubes do you reccomend trying? should i stick with groove tubes or are their any better ones i could go for?

the amp has 3 12ax7 tubes in the preamp and 1 12ax7 and 1 12au7 as driver tubes. could i possibly just be the driver tubes? and do i need to get both a 12ax7 and a 12au7?

sorry for the questions about the tubes, im not too clued up on them.

is there anything else it could possibly be thats wrong with the amp?

oh and also i understand that replacing preamp tubes is relatively simple as they dont need biasing, would the tubes that produce the tube gain need biasing?
 
#5
There's no definite answer when it comes to tubes. You gotta remember... tubes are fragile. Vibrations, bounces, hot-to-cold transitions, these can all age a tube prematurely. It's a variable.

My lead guitarist had issues with his old amp's tubes. Same deal. Just swap em. If you get the same symptoms soon, then it's definitely the amp. But this sounds like tubes going out to me.
 

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