Ampeg SVT 4 Pro schematic needed

[Jazz P Bass]

Any kind soul care to share a schematic for the SVT 4 Pro?
I have a preamp out signal. No output signal.
Went in power amp in with a result of no signal also.

[Tom Phillips]

I can email it to you if you PM me your email address that will accept attachments. Can't send attachments thru the Ampage email system
Tom

[Enzo]

Oh, I can fit it here in sections.

[Jazz P Bass]

Ampeg SVT 4

Thanks Tom.
Thanks Enzo.
So far the Output MosFets are not shorted.
The relays are going into protect for sure.

[Jazz P Bass]

Fixed

Got the SVT 4 fixed.
1 hour to take it apart.
1 hour to resolder the main board.(found a couple of really bad solder joints)
1 hour to put it back together.
1 hour to final test & do paper work.
Nice amp!
Why do people think this stuff is easy?

[Tom Phillips]

Yea. Everybody thinks the other guy's job is easy.
"All ya got to do is .... What's so hard about that."
"You charged me how much to solder two joints?"
Etc. etc. etc.

Glad you got the SVT fixed.

Regards,
Tom

[Lorenz]

Hi, I got same problem. Poweramp shut down in 20 second as it were over heated, and it's not. Relay switch off and fun starts cooling. No sound at the output. Turning off the amp, waiting 2 minutes and turn it on again and same scenario. Amp looks perfect and during operation works well. Anybody can help with an idea??

Thanks

Lorenzo

[Jazz P Bass]

Ampeg SVT

Lorenz

I can only advise what I did.
Remove the main board & look for bad solder joints.
Resolder the main components while your are in there.
Look at the filter cap soldering & the transistor joints. If the joint looks shallow, that is a good indication that the board was not preheated to a high enough temperature at the wave solder process.
You can tell sometimes if you see a recurring shallow solder joint.
Sometimes it will be the parts that are attached to ground.
Sometimes it will be one side of the board, or one side of the components.
Happy Hunting.
PS: you really should have started a new post.

[Lorenz]

Thank you Jazz, I start dismount the amp. It's strange it doen't seem to be a bad solder. Amp is really perfect and no sollecitation stop or start the problem. Now the problem is continuos. I think it could be a problem on the Breakoff Board, I'll try to change IC6 as it seem to controll relay on/off. I work in a repair shop and "hunting" for gost problem is my worst nightmare!!

Next time I'll create a new post ;-) and tell you my solution

Thanks again.

Lorenzo

[Mitchkilroy]

Im new here so i dont really know how these forums work, Any chance that someone here has a copy of the Power amp schematic for this amp(SVT4pro). Only thing i saw posted on here was preamp but i could be wrong, thanks

[Jazz P Bass]

Ampeg SVT4 Pro schematic

On this Post go up seven posts.
Enzo laid them all right out.

[Enzo]

The five files I posted should be the complete set of schematics and the board layouts. I may have left off the page that shows two speaker jacks wired together. But that is all that is on the page - two jacks.

Just click on each file to open it.

[Mitchkilroy]

sweet

Nice i found it, thanks. I didnt realize the pdf was multiple pages before. Thats probably one of the best schematic/part diagrams ive seen

[Englfireball82]

SVT 4 PRO Issue...

Hi, everyone.

I have a Ampeg SVT 4 PRO rack head that is having an issue of power amp A side isnt putting out any sound to the cabs neither through speakon or 1/4 inch outputs. Power amp B side seems to be working fine, however i need to use both sides to run to my cabs, Anyone have any ideas on what it could be? Thanks!

[Enzo]

When you first turn the amp on, there should be a brief pause before the speakers click on. Each channel has an output relay to connnect the speakers. I woulod wager one of your relays is not clicking on. And the probably reason is that the channel has failed.

But before we assume that, slide the MONO/BRIDGE switch back and forth a few times. ANy help? And since it is ch A not working, plug a spare cord from Preamp A out to Power AMp A in. ANy help?

You can also just plug a guitar directly into Power AMp A in. Got sound?