Having problems with my Ampeg SVT-3 Pro

[FuzzyPanda]

For the past couple months I've been having trouble with my Svt-3 Pro.

Back when I got it (About a year ago) I bought it used, and it sounded amazing. Fast forward to a few months ago, it started to sound horrible.

One day it just started to make a crackling sound, then, the tone I got with my regular settings was gone. No matter what I do to the EQ and settings, the amp won't sound good. It won't get bright or growly, and it lost its warmth.

I took my amp and cab in to be looked at, and the workers couldn't find anything wrong with the cab, or the head.

I've looked through all the other SVT 3 Pro problem threads, but I haven't seen anyone with this exact issue.

If anyone has any idea what could be wrong, and help is appreciated.

[WhoDidTheElf]

How old is it? The tubes may need to be replaced but it usually doesn't quite go that fast.

Try switching cables? Different cabs? Different basses?

[fenderhutz]

Did they check for cold solder joints? All 4 that I had replaced you could tap on the top with your hand and it would make the crackling sounds after a few months of use. A light open hand smack on top of the chassis.

That's when I knew I had to use the warranty AGAIN to get it replaced. Pro-Tec in Wash DC could never find a problem, and could never fix it.

[JimmyM]

3 Pros have MOSFETS that occasionally need biased. That could be it, and it could also be a bum tube. Try swapping your tubes around and see if the problem goes away. Fenderhutz's cold solder joint theory is also plausible.

[FuzzyPanda]

Originally Posted by WhoDidTheElf

How old is it? The tubes may need to be replaced but it usually doesn't quite go that fast.

Try switching cables? Different cabs? Different basses?

Its quite a few years old I think, and I've tried it through a bunch of different cables and different basses, haven't tried a second cab though.

I'll bring it to my tech, and ask about the Mosfets, the tubes, and the solder joints. Thanks guys.

[raytsmith]

You aren't using an active bass with a low battery by any chance ?

But yeah, make sure you try different bass, cord, cabinet, before you have someone open up an amp that may be OK.

[rodl2005]

try the suggestions above 1st. & report back.
just be sure to swap the same type tube with the same type tube.. eg. a 12AX7 with another the same. NOT a 12AX7 with a 12AU7 etc...
I can't remember which pre tubes are IN the 3 PRO..... just saying

[Jerrold Tiers]

There are tubes in the pre, and tubes in the poweramp also. Both 12AX7 and 12AU7 are represented. The mosfets are directly driven by a 12AU7.

Tubes do go bad, but crackly sound is often from bad solder also.