1975 AMPEG SVT - Issues (need help Video attached)

[coreyfyfe]

Bob - I've got a 1,200W dummy load (four 300W wirewounds) and even that gets warm in a short time!

OP - I hope your tech has been inside an SVT before (preferably many) and knows what he's doing. I've got three 70's SVT's and have serviced two of them. The first one I got 20 years ago bounced from supposed tech to tech before I finally found a guy who really knew his stuff and fixed it right. It wasn't cheap, though, so I decided to teach myself. Full recaps, plate, screen, bias resistors, etc. Any tube amp can kill you, but an SVT is a heavy, complicated, special kind of SOB that can kill you REAL good.

Was in a similar boat with mine. Went through repairs/rebuilds a few other amps before I attempted anything with my SVT. Mine ended up having a stray cap that was added around the phase inverter, likely to combat some noise issue at some point. The amp passed through a few techs trying to figure out that one but it kept cutting out and dropping signal shortly after I'd get it back. Eventually I sat down and just traced it out and couldn't find that damn cap anywhere, looked around at a bunch of other people's amp pictures, definitely shouldn't have been there. No idea when it was added but it's been problem free since (aside from the occasional noisy 6C4). Lovely amp.

 

[Rickenbackerman]

Yep, aside from those damn noisy 6C4's (and the weight), playing through a properly tuned up 70's SVT and 8x10 is a truly special experience.

 

[bobyoung53]

Bob - I've got a 1,200W dummy load (four 300W wirewounds) and even that gets warm in a short time!

OP - I hope your tech has been inside an SVT before (preferably many) and knows what he's doing. I've got three 70's SVT's and have serviced two of them. The first one I got 20 years ago bounced from supposed tech to tech before I finally found a guy who really knew his stuff and fixed it right. It wasn't cheap, though, so I decided to teach myself. Full recaps, plate, screen, bias resistors, etc. Any tube amp can kill you, but an SVT is a heavy, complicated, special kind of SOB that can kill you REAL good.

The guy I use used to do warrantee work on SVT's back in the 70's in Boston so I know he'll get it right. A lot of techs won't touch them, because they are heavy and are a PITA to trouble shoot. I bought a 70's SVT head when I was living in Lima Peru for 300 bucks about 12 years ago and had to teach myself how to fix them. I went through the same stuff as you did. Lima is or was the mickey mouse capital of the world, by buying the head there I learned that 6L6's will work in an SVT! haha! The head actually sounded like a big Fender when I first got it.

 

[Rickenbackerman]

6L6's might work, but maaan, they sure won't like it very much with 660+ volts on the plates!

I tried to take my first one to one tech that wouldn't touch it with a ten foot pole because he supposedly had one bite him and toss his rearend clean across the room while he was trying to bias it. How you can do something dumb enough to get nailed when biasing one, though, I'll never understand.

That amp always worked fine, but never really sounded "right". Muddy, undefined... man, that was a long time ago. I eventually took it to Pete Cage (of Cage Amplification) and he made it right. Pete does fantastic work, but it sure ain't cheap. I guess you get what you pay for, though.

edit: I almost forgot, before I found Pete I took it to a guy who is our alleged "SVT guru", who shall remain nameless. He charged me a small fee to look it over and said it was fine. I remember saying "you don't think it sounds muddy?" and he insisted that it sounded "just like an SVT should". I knew it still wasn't right, though.

 

[bobyoung53]

6L6's might work, but maaan, they sure won't like it very much with 660+ volts on the plates!
.

I thought it had been modded when I first got it home, there were old GE 6L6's right out of fender amps, I could see the claw marks on the tube bases. And if that wasn't bad one bias was set to zero and the other side was set pretty close to full and the tubes weren't glowing or anything. I was amazed when I realized it hadn't been modded and this one has 700 volts on the plates. It definitely sounded odd though, very clean like a Fender Bandmaster or something like that. I don't know how long it was run like that, not long I suspect but I ripped it apart, left it on the spare bedroom floor for a few months months and bought many new parts from Fliptops, had them sent to me and learned how to re-cap it, tune it up, check resistors etc. I never liked fooling around near the power tube or the power supply circuitry with it on though and still don't. I even got it on a plane and flew it back here (they were very nice to me at the counter in Lima Airport, didn't even charge me for overweight), I still use it along with another one I bought about 20 years ago here in the U.S. It was also wired for 220 so I had to figure out how to rewire it for 110 once I got it back, there's two taps on the primary of the power transformer at least on the old ones.
I also developed a new respect for old American GE tubes

 

[JMacBass65]

Bob - I've got a 1,200W dummy load (four 300W wirewounds) and even that gets warm in a short time!

OP - I hope your tech has been inside an SVT before (preferably many) and knows what he's doing. I've got three 70's SVT's and have serviced two of them. The first one I got 20 years ago bounced from supposed tech to tech before I finally found a guy who really knew his stuff and fixed it right. It wasn't cheap, though, so I decided to teach myself. Full recaps, plate, screen, bias resistors, etc. Any tube amp can kill you, but an SVT is a heavy, complicated, special kind of SOB that can kill you REAL good.

I have a hard time trusting techs of any sort. I do most of my own car work, bike work, home repairs, bass work......

You you get the picture.

That said - I just don't "get" electricity, and would never screw around with my SVT. Well, except when I was young and got mine - I replaced the power cable because it was missing the ground lead when I got it.

Anyway, what I am trying to say is - If my SVT ever needs work, do you do jobs for hire?