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#1 2012-04-03 21:56:57

churchman
New member
From: Colorado
Registered: 2012-04-03
Posts: 5

V4 what to look out 4

I just did a cap job and retube on a guys super reverb and he gave me a 74 V4 and blackface bassman cabinet for payment. It is all original except maybe one part. The death cap was blown. I know better than to turn it on. I just ordered the filter caps from antique. Tested the GE 7025's and they have life left. I'm sure I will put chinese pulls in when it's ready to power up.

So I've been through several amps and own a SVT as well. I have read much of the bias supply on these and issues people have faced. I guess you hear the bad. I probably will replace the .33 coupling caps and redo all the bias supply. 

Are parts going to start crapping when it gets going again. Should I worry about stuff going wrong. Are those flyback diodes junk? Other than the filter caps how much of a sacrilege is it doing part replacement. I mean this is original. I had it listed for $500 as is and being vintage at heart I couldn't sell with out getting it working. Although I possible will after the cap job.

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#2 2012-04-06 17:17:07

Liquids
Member
From: CT
Registered: 2010-08-01
Posts: 491

Re: V4 what to look out 4

Are parts going to start crapping?  Maybe.  Take a picture.  Steve/hangman may know just by the year what to expect in terms of quality of the coupling caps - but a photo will definitely help him know if they are the 'crap' or 'somewhat reliable' coupling caps you have.

Steve says get rid of the flyback diodes...I would personally replace them with equals or equivalents.  More and more amps are using them more and more (including the trainwreck amps built by ken fisher, who worked at ampeg for a time), and the best tech I know says he puts them in everything he builds, says they're sometimes lifesafers.

Don't worry about vintage sacrilege - it's not that kind of amp like fenders and marshalls where the old components are thought to have the mojo and their presence or having been replaced is a major $value$ factor for the market.  Get the amp as stable, playable, up to speed as you can.

If you are selling it, and you are a tech either full time or on the side, your reputation goes with you on that amp, and will potentially 'encounter' everyone the future owner talks about the amp with - especially if he needs to take it back to a tech anytime soon.  All the more reason to leave no guesses about the reliability of the components that the amp sells with. 

I'd do all the coupling caps.  The xicon/panasonic brown ones you can get through weber and tubesandmore.com are cheap, and plenty good IMO. No reason to doubt them, they just don't fetch the mojo of the yellow mallorys or orange drops.


Matthew

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#3 2012-04-14 20:59:28

churchman
New member
From: Colorado
Registered: 2012-04-03
Posts: 5

Re: V4 what to look out 4

Well I replaced all the electrolytics, went through the bias supply and replaced c16 and electrolytics and diode, I was about to replace the flybacks so guess I'll return to that, read about the coupling caps to the power tubes and replaced them. Brought it up with a variac, fired it up and played it at low volumes for a half an hour, guitar and bass. It works good. I really have to many amps and I don't gig. But the condition of the amp is superb, no rust at all, all original tubes, or american replacments.
OP tranny dates to late 73 and the power early 74, reverb, metal toggles, aluminum knobs.

I have been repairing amps as a hobby for 15 years, I have done repairs for other people for free, mainly freinds, but now I have a Blackface Vibrolux coming in so I am going to start charging.

The amp is west of Denver, I do have a buyer but I don't know if he still wants it or if I can sell it now.
Thanks for the reply Liquids,  I will update as I use it more.

Now it's a dilema.

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