SVT-4 Pro cutting out

rick1651 · Tadpole Joined: 30 Sep 2005 Posts: 17

I bought a used SVT 4 Pro awhile back and it has been playing great. I have only used it in a studio setting, no actual cranked up gigging yet. Just recently I noticed the red Peak light comes on sporadically and completely mutes the speakers. Its the same light that comes on when you hit the mute button or when the input is overdriving the preamp and you need to back off the Gain. I was using a footswitch to mute the amp and thought that maybe the switch has a short. I unplugged the switch and it seemed to play fine for awhile, but now its starting in again. Could this be something as simple as a bad preamp tube, or am I looking at something more serious. Anybody got any thoughts on this?
Thanx
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Playing my bass a day, helps keep the blues away.
(Unless its da blues your playin')

MusicMan Stingray 5
'76 4001 Rickenbacker Custom
'75 American Fender Jazz

God of Rapture · Posted: Sun May 07, 2006 6:34 pm Post subject:

While i am not 100% sure what is causing your problems. I do know that those 4Pros have a terrible time with overheating.

Make sure it is well ventilated.

rick1651 · Tadpole Joined: 30 Sep 2005 Posts: 17

Hey GOR,
Nice to hear from you again! My 4 Pro is in a rack case, but it is pretty well ventilated. I guess it could be heat, but when it cut out last, I felt around the casing and it didn't feel too hot at all. Like I said, I'm not really pushing the amp too hard. Maybe it's time it had a little check up.

Thanks for the reply,
Rick
_________________
Playing my bass a day, helps keep the blues away.
(Unless its da blues your playin')

MusicMan Stingray 5
'76 4001 Rickenbacker Custom
'75 American Fender Jazz

God of Rapture · Posted: Tue May 09, 2006 7:06 am Post subject:

I believe the 4Pro has its vents on the side (Dumb idea) so putting it in a rack without vent holes on the side really kills it.

My 3Pro has the vents on the back. I have never had an issue with overheating.

There were lots of threads about the 4Pro overheating on the Ampeg forums when it was still around.

Good luck finding the problem man. Diagnosing stuff like that can be such a pain.

rick1651 · Tadpole Joined: 30 Sep 2005 Posts: 17

Thanks dude,
But if you remember back a few posts, I mentioned that I completely streamlined the SKB case with vent holes and fans. I tried playing with the amp completely out of the rack case, and it did it again, after about 30 minutes. I felt the case and it was barely warm. So heat is not an issue. I spoke to a guy who fixes amps and he said it sounded like the jack that you plug the footswitch in, to control the Mute, maybe bad or just needs to be resoldered. About 75-100 dollar fix. Personally I think I got a bad component in there someplace that starts to sputter after it warms up. Either way, it needs to be fixed. Awfully hard to annoy the neighbors if I can't make with the boom boom! Thanks for alway replying to the posts. You're a good man.
_________________
Playing my bass a day, helps keep the blues away.
(Unless its da blues your playin')

MusicMan Stingray 5
'76 4001 Rickenbacker Custom
'75 American Fender Jazz

rick1651 · Tadpole Joined: 30 Sep 2005 Posts: 17

In case anybody reading this post has had the same issue, it was simply a bad solder joint on the mute jack. A simple fix but not one I was willing to do myself. I have a lot of experience soldering and fixing circuit boards and wiring, but this jack is located on the "motherboard" and you practically have to take the entire amp apart to get to this board. I took it to a local amp guy and it took him about an hour to fix it.
_________________
Playing my bass a day, helps keep the blues away.
(Unless its da blues your playin')

MusicMan Stingray 5
'76 4001 Rickenbacker Custom
'75 American Fender Jazz