Ampeg svt-3pro issue....HELP!!!

randysmojo · #1 08-06-2011, 06:03 PM

I have an older svt-3pro with the blue and red logo. It will cut completely out at times and I noticed the "peak" light lit up when it happens. When the light goes off, it works again. I turned it up at home for a long time and had no problems, but during sound check tonight it did it again. I had to di into the board for the show. Has anyone seen an issue like this with an ampeg? If so, do you know what it is? I don't have money for the expensive amp guys around here.

**B-string** · #2 08-06-2011, 06:29 PM

I know Jerrold Tiers worked with someone here before about this. JimmyM should be along and shed some light and/or PM JT.

randysmojo · #3 08-06-2011, 10:45 PM

Thanks, B-string! If it helps at all, when it cuts,out the direct out cut out too.

**B-string** · #4 08-07-2011, 12:13 AM

Quote:

Originally Posted by randysmojo

Thanks, B-string! If it helps at all, when it cuts,out the direct out cut out too.

That also sounds familiar! I tried the search but came up empty. I know I remember it. If I had the schematics I might be of more help, I guess we'll wait for JT.

JimmyM · #5 08-07-2011, 12:33 AM

Ya, don't be waiting for me...all I know is how to get rid of distortion by biasing the mosfets occasionally. This is way above my head!

lokikallas · #6 08-07-2011, 12:59 AM

Sounds like a trip to the repair shop is in order. That is not normal or even a common symptom.

Foz · #7 08-07-2011, 01:13 AM

Caig dexoit and a thorough cleaning of the send/return jacks?

These jacks usually do some switching and if dirty can interrupt the flow of the funky goodness.... not a problem specific to the unit but a common problem easy to check out.

randysmojo · #8 08-07-2011, 03:30 AM

It's happen now once with nothing in the effects send/return and once when something was. Would that make a difference if it was dirty jacks?

rickdog · #9 08-07-2011, 09:00 AM

Quote:

Originally Posted by randysmojo

I have an older svt-3pro with the blue and red logo. It will cut completely out at times and I noticed the "peak" light lit up when it happens. When the light goes off, it works again. I turned it up at home for a long time and had no problems, but during sound check tonight it did it again

I think the "peak" light is a big clue. On my newer (2002) 3PRO, this comes on when the mute is engaged. So I'd suspect something in the mute circuit.

Any chance you plug in an external mute switch on the gig but not at home (or vice versa)? If so, the problem could be in the switch or the jack.

It's also possible there's a problem in the mute switch on the panel.

randysmojo · #10 08-07-2011, 11:56 AM

I didn't plug in a external switch either time, but I wonder if the on board switch happens to be the problem, does an external switch bypass it?

rickdog · #11 08-08-2011, 08:05 AM

Quote:

Originally Posted by randysmojo

I didn't plug in a external switch either time, but I wonder if the on board switch happens to be the problem, does an external switch bypass it?

A quick glance at the schematic says "no".

But that brings up another point: try plugging in and removing a phone plug in the footswitch jack - maybe the problem is in the switched jack.

randysmojo · #12 08-08-2011, 10:10 AM

The footswitch jack is 1/4". I plugged a guitar cable in it and ut instantly muted the rig. I didn't have a foot switch handy to try to see if it works, but I will try to dig one up tonight. Of course I cranked it for an hour or more yesterday and it didn't happen again. Intermittent problems are the worst!!!

Jerrold Tiers · #13 08-08-2011, 05:53 PM

As I said in the PM.... Sounds like something in the mute.

Footswitch jack is a possible, yes. Broken solder joints in the mute do that too.

randysmojo · #14 08-09-2011, 07:34 AM

Here is where it sits. I fixed the cold solder joints, but my pictures of the wires from the transformer didn't turn out so I can't tell how to hook all the wires up. The ones I'm still missing on are just the black and white wires from the transformer, and the black and white wires from the switch. I got the ones from the switch that plug in by where the power goes to the board, but the other two I can't tell. I know where they go, but not what order. All I need is out of the black and white wires from the transformer, which one is closest to the outer edge of the board, and out of the black and white wires from the switch, which one goes closest to the edge of the board. If anyone can tell me or even have the heart to pop open the top of theirs and check or send me good pics of it, it would save me so much heart ache! I'd hate to be wrong and try to turn it on just to fry it after all this!

randysmojo · #15 08-09-2011, 11:57 AM

I got the schematic for the power supply, so I will see if I can get this thing back together!!