Ampeg SVT lll

[Mars Amp Repair]

Yeah thanx again tom.
That schemo held the clue I needed to solve the mystery...funny how sometimes everything you come up with points in the direction of the solution...It's just connecting the dots from there to the cause that can be a bit difficult sometimes.

glen

[wizard333]

I got the info, thanks Tom!

[Mars Amp Repair]

What did you find?

Just curious what you found with your SVT 2 pro g

WOW, I'm looking at an SVT3 with pretty much the same symptoms. I dont have a schematic either, if you could forward one that would be grand. It has all 12AX7s so most likely the same issue...... If I'm looking at the amp from the front, there are 2 tubes on the power amp board, next to each other, one closer to the front once closer to the back. There are 3 on the preamp board, lets call them 1,2,3 from left to right. Which is supposed to be the 12AU7?

Thanks!

[wizard333]

Exact same thing; someone re-tubed it and didnt put the AU7 in the right socket.

It works better with the AU7 where it is supposed to be, but for the life of me I dont hear a helluva lot of difference with the "tube gain" knob cranked vs with it all the way down; very slight decrease in headroom is about it. Overall its a pretty good sounding amp though, it has that Ampeg tone. I play tested it as I do with everything that comes through here and I am tempted to ask what he wants for it (its something from a bass store not someone's personal piece).

On another note, I'm passing through your neck of of the woods later in the week, I'd be curious it you were going to be around so I could stop by and say hi. What is your phone # there in Englewood?

Thanks!

[FeyD]

I am having same issue. Would someone send me the schematic as well?
Thanks in advance...

Also, there seems to be a real issue with getting parts from St. Louis Music for this amp. Can anyone suggest an alternate supplier for transisters and other parts?

Again, thanks...

[Enzo]

St Lous Music was bought by Loud Technologies - the MAckie people.

But I would only use them for things that are specifically AMpeg. Transistors are transistors, get them from Allied, or Mouser, or Digikey, or wherever.

What parts are you having trouble finding?

[FeyD]

Actually, the Ampeg service rep in my area can not seem to get the parts. He has had my rig for over a month now and to his credit it does appear to be an issue with Ampeg. I got an email from Ampeg stating they do carry the part in question but had to send 2000+ back for "regrading".

So at this time Ampeg does not have the part in stock.

I am looking for the output transistors (IRFP240). At least that is what the tech has told me. The tech seems really reluctant to buy the parts anywhere else for some reason but at this point I really need to get the amp up and running and according to Ampeg it is still going to be more than a week before they can ship the parts we have requested. If you could provide me with a recommend supplier and part number perhaps I can convince the tech working on my amp to purchase from some other reseller.

Again, thanks in advance.

[Mark Black]

The fact that Ampeg sent the parts back for "re-grading" actually gives me hope.

Those output MOSFET's need to be fairly well matched to each other, otherwise one or a few will hog all the current & be doing all the work leading to premature failure. After the Loud Technologies buyout Ampeg quit supplying the graded versions of these, leaving all of us to over-order parts from an electronics vendor in hopes we could come up with a reasonably matched set out of the bunch. That usually leaves a bunch of useless orphans and is wasteful, which is why they will cost more from Ampeg (after grading) than from standard parts houses.

Sorry, but I would suggest waiting for the graded parts to be available for a quality repair.