Ampeg SVT 4 Pro schematic needed

Jazz P Bass · 10-31-2009, 03:15 AM

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 · 10-31-2009, 04:36 AM

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 · 10-31-2009, 06:13 AM

Oh, I can fit it here in sections.

Jazz P Bass · 10-31-2009, 02:16 PM

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

Jazz P Bass · 11-01-2009, 01:12 AM

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 · 11-01-2009, 01:52 AM

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 · 12-11-2009, 12:04 PM

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 · 12-11-2009, 06:14 PM

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 · 12-11-2009, 06:28 PM

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 · 02-25-2010, 03:28 AM

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 · 02-25-2010, 04:03 AM

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

Enzo · 02-25-2010, 06:33 AM

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.

10-31-2009, 03:15 AM	#1
Jazz P Bass Senior Member Join Date: Dec 2008 Location: Wernersville, PA Posts: 731	Ampeg SVT 4 Pro schematic needed 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.

10-31-2009, 02:16 PM	#4
Jazz P Bass Senior Member Join Date: Dec 2008 Location: Wernersville, PA Posts: 731	Ampeg SVT 4 Thanks Tom. Thanks Enzo. So far the Output MosFets are not shorted. The relays are going into protect for sure.

11-01-2009, 01:12 AM	#5
Jazz P Bass Senior Member Join Date: Dec 2008 Location: Wernersville, PA Posts: 731	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? Last edited by Jazz P Bass; 11-01-2009 at 04:57 PM.

12-11-2009, 06:14 PM	#8
Jazz P Bass Senior Member Join Date: Dec 2008 Location: Wernersville, PA Posts: 731	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.

02-25-2010, 04:03 AM	#11
Jazz P Bass Senior Member Join Date: Dec 2008 Location: Wernersville, PA Posts: 731	Ampeg SVT4 Pro schematic On this Post go up seven posts. Enzo laid them all right out.

10-31-2009, 04:36 AM	#2
Tom Phillips Senior Member Join Date: Jun 2006 Location: California, USA Posts: 676	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

11-01-2009, 01:52 AM	#6
Tom Phillips Senior Member Join Date: Jun 2006 Location: California, USA Posts: 676	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

12-11-2009, 12:04 PM	#7
Lorenz Junior Member Join Date: Jun 2009 Posts: 2	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

12-11-2009, 06:28 PM	#9
Lorenz Junior Member Join Date: Jun 2009 Posts: 2	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

02-25-2010, 03:28 AM	#10
Mitchkilroy Junior Member Join Date: Feb 2010 Posts: 1	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

02-25-2010, 06:33 AM	#12
Enzo Senior Member Join Date: May 2006 Location: Lansing, Michigan, USA Posts: 10,283	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. __________________ Education is what you're left with after you have forgotten what you have learned.

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