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SVT help needed!

S

Scarvin1

Mar 29, 2009
7
3
#1
Last night I picked up a '76 SVT from a guy on craigslist. I pulled and checked all the tubes. All are okay. Plugged the amp into my current limiter and something is shorted. No filaments, lights, nothing. As I've never worked on one of these before, Any advice as to where to start would be appreciated!

Thanks in advance...

Mike
 
#3
Thanks for the reply and sage advice!

I do have some experience working on amps, but mostly old Fenders and Gibsons. I know that SVT's can be quirky and am just looking for anything typical that could cause this issue.

Thanks again!

Mike
 
#4
Scarvin1 said:
Last night I picked up a '76 SVT from a guy on craigslist. I pulled and checked all the tubes. All are okay. Plugged the amp into my current limiter and something is shorted. No filaments, lights, nothing. As I've never worked on one of these before, Any advice as to where to start would be appreciated!

Thanks in advance...

Mike
Click to expand...

Did you check the power line fuse?? What is your current limiter? how did you check the tubes for "okayness"?

Paul
 
#5
Fuse is ok, Tubes tested on a hickock 6000a. Problem was solved when I noticed the connecter from the preamp to the power amp worked itself out a little. Pushed it the rest of the way down and success! A little embarassing though :rolleyes:

Mike
 
#7
Scarvin1 said:
Fuse is ok, Tubes tested on a hickock 6000a. Problem was solved when I noticed the connecter from the preamp to the power amp worked itself out a little. Pushed it the rest of the way down and success! A little embarassing though :rolleyes:

Mike
Click to expand...

yeah, they don't work very well with that multi connector disconnected. ;)
glad you got it sorted..... :)
 
#9
Some pics...

DSC00871.gif


DSC00867.gif


DSC00868.gif


DSC00870.gif


Sorry, I forgot to take pics of the sextet of RCA 6550's!

By the way, does anyone have a source for those knobs? Looks like I could usr one.

Mike
 
#15
Thc caps are original. I ordered a new set from Fliptops along with the knob. I also heard that the solid wires to the pc in the pre and power amps should have the solder reflowed. Another oddity in this amp is that there are no 12DW7's. Only 12AX7's. The tubes look original. Is that normal?
 
#17
Yep, the center, tan colored cap is identical to the ones found in my unmodified 70/71 traynor bassmates.
hey jimmy i had a questions about the fixed output in the 69 svt thread - were the fixed output cable with 4-pin din style connector used in the pre 6550 tube models only? what year did they phase that out? were there any early 70's black line which pre-date the normal output jack?
 
#18
yes there are. my first 73 810 that gor burned up had a 4 pin connector on it. can't remember if the head had it, and i don't know if the svt did either. but it was gone by 74 when magnavox took over.
 
#19
It's always possible that it has been modified to not use the 12DW7.... That is the infamous "12AX7 mod".

If you just stick in 12AX7 in original circuit, I don't think good results will be had... never tried it though.

It can be reversed to original if it was done. Somewhere I probably have the document on the mod, which would save checking everything part-for-part to see. But don't hold your breath, and I don't have it in PDF
 

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