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previous: Marc I would appreciate some advice on a... -- 9/16/1999 9:57 PM

Re: Ampeg SVT opinions

9/17/1999 5:17 AM
Bruce	Re: Ampeg SVT opinions Marc, do you have your SVT schematics ready? Clean the thing out because they seem to attract dirt like no other amp I've ever worked on!! Greasy beasts they are. EI's are OK if you get lucky but I've had a few bummers from them. First thing: replace ALL the first filter E caps with what ever will give you at least 50uF at 900v to 1000v! More uF is OK to a point. I use two series 100uF/500v caps for that section. No sweat. LCRs have a common ground (tricky if it's a multicap)...but they make singular 500v caps too. Go over and make up what you need in uF/Vs to replace the other awfull E-caps they used in there! Then flip the thing over and remove ALL the 10 ohm and 22 ohm power resistors on the plates and the screens (current limiting resistors). Replace what ever is there with LKQ (like kind & quality)... some amps were different but they all get majorly stressed when the power tubes blow up (which is regular when not set up right)... replace them all with known good ones and don't cheat. Check the sockets of the power tubes to see if there has ever been a flash over on any. Put new in if so. Rivets YUK! You might want to check the 1ohm cathode resistors and make sure they are still really 1ohm. The balance and bias adjust relies on them being pretty close to right on. Don't pull too much current at idle through the tubes. The probes measure mv of DC through those 1 ohm resistors so your DVM should be set to read DCmv. Milivolts measured here will mean miliamps now. About 60ma to 70ma for three (one side) is close to right at this VERY high plate voltage. Use the other pot to balance the two halves as close to the 60ma to 70ma as you can. CAREFULLY! Don't load this amp lopsided with too much current. Pay attention to this amp and respect it's power because the power supply is capable of some serious voltage at high current and can damage or stop your heart if you even get mildly poked by it. If you are new to this kind of DC power, have somebody nearby incase you have an accident. I've NEVER worked on an SVT that didn't pump out at least 280watts (or more) of pure tube horsepower!! KT88s are very cool in these too. Bruce

9/17/1999 5:17 AM

Bruce

Re: Ampeg SVT opinions

Marc, do you have your SVT schematics ready?

Clean the thing out because they seem to attract dirt like no other amp I've ever worked on!! Greasy beasts they are.

EI's are OK if you get lucky but I've had a few bummers from them.

First thing: replace ALL the first filter E caps with what ever will give you at least 50uF at 900v to 1000v!

More uF is OK to a point.

I use two series 100uF/500v caps for that section. No sweat.

LCRs have a common ground (tricky if it's a multicap)...but they make singular 500v caps too.

Go over and make up what you need in uF/Vs to replace the other awfull E-caps they used in there!

Then flip the thing over and remove ALL the 10 ohm and 22 ohm power resistors on the plates and the screens (current limiting resistors).

Replace what ever is there with LKQ (like kind & quality)... some amps were different but they all get majorly stressed when the power tubes blow up (which is regular when not set up right)... replace them all with known good ones and don't cheat.

Check the sockets of the power tubes to see if there has ever been a flash over on any. Put new in if so. Rivets YUK!

You might want to check the 1ohm cathode resistors and make sure they are still really 1ohm.

The balance and bias adjust relies on them being pretty close to right on.

Don't pull too much current at idle through the tubes.

The probes measure mv of DC through those 1 ohm resistors so your DVM should be set to read DCmv.

Milivolts measured here will mean miliamps now.

About 60ma to 70ma for three (one side) is close to right at this VERY high plate voltage.

Use the other pot to balance the two halves as close to the 60ma to 70ma as you can.

CAREFULLY! Don't load this amp lopsided with too much current.

Pay attention to this amp and respect it's power because the power supply is capable of some serious voltage at high current and can damage or stop your heart if you even get mildly poked by it.

If you are new to this kind of DC power, have somebody nearby incase you have an accident.

I've NEVER worked on an SVT that didn't pump out at least 280watts (or more) of pure tube horsepower!!

KT88s are very cool in these too.

Bruce

Replies:

Marc Thanks Psycho and Bruce!I d... -- 9/17/1999 3:04 PM