Ampeg SVT ISSUES . . . HELP PLZ!

[Lt_Nemo]

I recently scored an old Ampeg SVT II (non-pro). It is safe to say that I LOVE it! However, after an hour or so of playing through it, it cuts out.
Let me explain.. ..I though the speakers were busted at first, but found it strange that such a theory was A) physically impossible at the volume and B) strange that all the speakers would have to have busted at the same time. It was a "loose" and "airy" sound with pops and crackles. But the closer I listened, the sound would jump in and out. After a minute or two, it cut back in at its normal sound.
It happens now after a while of playing. I can turn it off and back on and get a good sound for all of 3 minutes maybe before it happens all over again. The volume significantly decreases and the speakers all crackle and pop and sound destroyed, then come back in sounding perfect.

Is the amp head overheating or not getting enough ventilation, is it a loose connection, or is it some other problem?

It is easily the best amp head i have played through when it works, so I would love to see it fixed..

 

[dmrogers]

I "think" what you are experiencing is a tube issue. The SVT III Pro that I had started doing the same thing after many years. I sold it to my dad and it is still doing it. However, it only occurs when it is first turned on. Then it is fine for the rest of the gig.

One of my Peavey Classic 50 does the same thing almost exactly. It is very old and has the original tubes.

The only difference from your experience, my heads do this within a few minutes of turning it on and only last for less than 30 seconds, AND it doesn't do it all the time.

It is my theory that it does it after the head has set up for a LONG time.

The sound is similar to a scratchy pot.

 

[Duke21]

It is soon morning in the east coast USA, Jimmy?

 

[anderbass]

You might just have dirty switching contacts in your Poweramp In jack. An easy test for this is to simply patch a guitar cord between your Preamp Out and Poweramp In jacks on the back of your amp. Doing this bypasses the switching contacts.

 

[JimmyM]

Tube, dirty effects loop jacks, and caps going bad are all possibilities. Hard to tell without being there, though.

 

[GrinningMouth88]

sounds like a dirty input or effect loop, my 700rbII was doing a very similar thing until I took it in for maintenance. 30 bucks later I have stronger solder points, clean pots, and clean inputs. Sounds good as new! Try that radioshack tv tuner stuff I forget the real name.

 

[JimmyM]

Is the Radio Shack TV stuff safe to use on pots? I know they do sell a contact cleaner that is, but I forget the name of it, too.

 

[Tim1]

A while ago I had an SVT 2 non pro with the identical issue. Turned out to be one of the white push button switches on the front had turned bad.

 

[jmpiwonka]

Have an svt2 non pro that was doing the exact same thing. Tried a short cord in the jacks and it didnt help. Had it checked out by my tech and he said it wouldnt pass a signal but tue problem was just corroded preamp out/ amp in jacks on the back.

No issues since those were cleaned.