SVT 4 Pro Issue

I have an SVT 4 Pro which I bought new about 12 years ago and it has worked flawlessly until about a month ago. I was playing a gig at the Ramona Mainstage opening for Gary Hoey and during the sound check the amp started cutting in and out. I changed guitars, instrument and speaker cables and finally just had to run direct into the house PA, which sucked by the way. The next day I turned on the amp at home and left it on for about 10 hours, randomly playing through it throughout the day. It worked flawlessly which made me think that the problem might have been the cable they used to plug into my direct out from the house system, which really doesn't make much sense to me.

About a week later I did a gig at the county fair and it performed without an issue which made me sure that it was indeed the venue's cable. Well, I played another gig at a small venue a couple nights ago with out any cables plugged into the direct out and it started doing the same thing but this time it did not only cut in and out, it would also make my volume drop about 30% from time to time.

Just to make sure my cabinet was not the problem, I played another gig last night using my backup rig with the same cab and everything worked fine.

Any clues?

 

I thought about a heat related issue but the first time it happened I was in an air conditioned venue and it acted up during the sound check. The amp was on for only about ten minutes. The next day, I left the amp on for about ten hours without an issue. As far as power problems at venues, I have played hundreds of venues over the last 12 years with this amp, including the ones where the issues occured without issues.

 

I'll check the input connection out and see if there are any loose wires or bad solder joints. But I did try wiggling the instrument cable that's plugged into the input without any results.

 

Even though I don't use the FX loop?

 

Hmm... I'm a lil confused. If the effects loop is never used, why would it matter if the contacts are corroded? I guess I'm not sure how that circuit is wired. If you can explain, that would be great.

 

Ok, that makes perfect sense to me now. Something I never even thought about. I'll check out the contacts and clean them. I have never once plugged into the effects loop so yes, they are probably corroded. Hopefully that is the problem. Fingers crossed. Thanks!

I have a gig in a couple weeks opening for Jefferson Starship and one in October with Billy Sheehan/Mike Portnoy and really don't want to use my backup rig so hopefully I can get this issue resolved.

 

Thanks! Being an intermittent problem, it will probably take a few gigs or rehearsals to see if that fixes the problem but that sounds like it could definitely be the culprit.

 

Ok, I went ahead and pulled the top cover off and located the effects loop jacks. They are not exactly the same as the ones in the link that Floyd Eye posted. The contacts appear to be made of stainless spring stock and look to be free of any corrosion or dirt.

 

So how did you correct the problem? Did you just clean the jacks?

 

Well this is an intermittent problem. Right now, I'm waiting for the amp to start having the issue. At that point I will put a cable in the effects loop to see if the problem goes away.