I need help troubleshooting my amp

c9h13no3 · #1 07-18-2010, 11:22 AM

I've got an Ampeg SVT-3 Pro head that I bought a few years ago. One day it just stopped working...maybe just over a year of light use. I discovered I could make it work by turning the gain knob all the way up and then hitting the strings pretty hard a few times. Then I could readjust the gain and it would work normally for a while, and after a bit, the volume would drop off, then come back up.

I plugged in to the power amp in and it worked just fine, so I'm pretty sure the problem is in the preamp, but from here, I don't know where to go as far as troubleshooting. The tubes all light up, so they should be working.

Any ideas on what I can take a look at? I don't want to take it to a service place if I can fix it myself, and if I do, I'd like to have a good idea of what specifically is wrong so I don't have to pay as much.

BassmanPaul · #2 07-18-2010, 11:28 AM

Take it to a tech. Don't damage it more by trying to fix it yourself.

Paul

Rick Auricchio · #3 07-18-2010, 11:53 AM

Quote:

Originally Posted by c9h13no3

The tubes all light up, so they should be working.

That statement proves you should take it to a tech.

If a tube filament does not heat up, it's definitely bad. But the converse is not true: Just because it lights up, that doesn't mean it's good.

c9h13no3 · #4 07-18-2010, 12:29 PM

Tech it is. All the connectors look good, nothing looks/smells overheated or burned, so I guess I've done all I can do.

johnk_10 · #5 07-18-2010, 12:55 PM

i would try plugging a short 1/4' to 1/4" cable from the preamp out into the power amp in (send/receive jacks) and see if it works that way. if it solves it, you need to clean the switches in the jacks (inside of the amp).

2 cents..............

Jerrold Tiers · #6 07-18-2010, 07:07 PM

What johnk_10 said......

Could also be a bad solder joint of the input, various folks have said they had a similar problem and it was fixed that way.

But the pre out / power amp in jacks are the prime suspect, along with the effect send/return. try the plug trick on both.

Rick Auricchio · #7 07-18-2010, 08:34 PM

I forgot about the send/return jacks...there's a good chance that's what it is. A high-gain burst often punches through oxidation on the jacks.