ampage Tube Amps / Music Electronics	For current discussions, please visit Music Electronics Forum.

ampage archive

Vintage threads from the first ten years

SVT parts

:

3/6/2004 11:13 PM

I have a selmer time ampeg SVT for repair. The standby switch was bad and one of the 6550 shorted and took out the 5ohm 5 watt resistor in the plate line. The unit looks like it might never have been worked on before. I pulled the bad tube and one on the other side. I then powered up the amp into a 4ohm speaker. The amp works like this but it hums alot. It seems the PS caps might be bad.

Here are the parts question. Are there any good caps that fit the SVT advaible plate and screen supply, low ESR and true voltage rated. Also what brand 6550 tubes will hold up in a SVT. I am working on this for a friend and they want to try to keep the price down: However if that can not be done let me know.

FWIW they found it at a garage sale for $25.00!

Psycho Bass guy or KG you around?

Gus

3/9/2004 10:16 PM

Holy Cow! $25!!! What a great price! I'm not sure about the caps, but I would be interested in finding out what people are doing so I can update my SVT at some point. As far as the tubes go, I've been using some real Svetlana or Winged C as they are now known 6550C's in mine for several years, and TimV on here also has one with those tubes and both work fine and sound great. If you have the $ I'd spring for NOS GE 6550's as they sound better, but for well priced, new manufacture, you can't go wrong with the Svetlana Winged C 6550's. I think you can get them from Antique Electronics Supply.
Hope that helps!
Greg

3/11/2004 5:51 PM
gus	Thanks for the tube information. I will also check the hum bal pot to make sure it is working. Gus

3/10/2004 7:27 PM

I'm not sure what other people would recommend for the caps but I used sprague for the 30uF 600V but they have a 20uF which works fine. I also used some of the lcr or now JJ can caps and other sprague internally for the values. The older ones get pretty cramped internally with all the caps needed and I haven't taken the time to figure out a space saving way to recap them. One nice thing about the MTI and later ones is there are more chassis mounted can caps so they don't take up all the room inside the chassis. The svetlanas are a good call and if you get them from Lord Valve they are less than 150 for the six. Did you adjust the hum balance to minimize the hum? Also check the bias and make sure it is equal on both sides. It is a good bet to replace the caps anyway though. I would guess around $200 or so for the caps and tubes to get it up to par. Clean out the sockets and pots and switches while you are in there too. There is one filter cap up in the preamp chassis also. Good luck and great find for $25.

3/10/2004 8:15 PM
Greg Simon	Hey Tim, I forgot to ask you if you brought the caps up on a variac when you replaced them, or did you just hit them with the high voltage from the get go? Greg

3/11/2004 8:32 PM
timv	I've never used a variac and have read a few times that new caps shouldn't need them. It isn't a bad idea though just to be sure.

Page 1 of 1