Need some advice on "restoring" an amp

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PhatTele
Junior tube assistant
Posts: 12
(3/20/04 5:39 pm)
 Need some advice on "restoring" an amp
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 A friend of mine asked me to work on an old Rickenbacker Model M-11 amp. He wants me to get it working for him. It had been sitting in someone else's shop for about a year...now I've got it. I can see why it sat around. It's a true point-to-point circuit with a simple no-eyelet (just holes) board used to separate the component leads. The board is original, it has yellow Astron caps, and carbon comp resisters. However, at some point in its history, somebody tried to "fix it." The cap can has been replaced, some of the leads are obviously replaced, and there are a lot of strange ground leads that don't look original to the amp. Meanwhile, the amp doesn't work at all. It just buzzes with no real output. I tried to map the existing components and leads to see if the layout matches the schematic I have access to, but nothing matches.

So, here's my issue: I'd like to get this amp working. I know that this particular amp was nearly the same thing as a Fender Deluxe 5D3 (rather than a 5C3 which is what the official schematic shows...at least that's what a visual inspection of the actual wiring suggests). I could easily restore it to that 5D3 circuit by building a turret board, possibly even using the original components (or rebuilding it with new components), attaching new leads, and using the existing sockets and transformers. However, I don't want to that if it's going to destroy any potential value this amp has being "vintage."

I'm not sure how much money my friend has in the amp...maybe a couple hundred bucks. What recommendation would you have me give him? Is rebuilding the amp from the ground up using as much of the orginal material as possible and following a known/related circuit a valid option here? It's going to be a mess to fix otherwise (now I know why it sat in the other shop for over a year).

Thanx...


 
Tiny Daddy
I will work on all amps
Posts: 565
(3/20/04 7:50 pm)
 Re: Need some advice on "restoring" an amp
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 There's a schematic here:
www.cnjradio.net/ricamps/m11.pdf
A couple of parts do not have values. Maybe you could supply the values for us.

Edit: Get rid of that .05uF from power line to chassis and install a 3-wire line cord.

Edited by: Tiny Daddy at: 3/20/04 7:53 pm
 
PhatTele
Junior tube assistant
Posts: 13
(3/20/04 8:49 pm)
 Re: Need some advice on "restoring" an amp
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 Tiny Daddy - Thanks. That the same schematic I've been working from. Except for a few value changes, that circuit is almost identical to the Fender Deluxe 5C3. Unfortunately, this amp never had octal sockets in the preamp. It's always had 9-pin sockets. There are no cathode bypass caps in this amp. My guess is that it is some sort of 5D3 Deluxe. So, when I restore it or rebuild it, I'm going to have to build it along the lines of a 5D3.

I'm curious though, should I rebuild it with a new board (so it can be easily serviced later on)? As it stands now, whichever schematic or layout I use, it will not match what's in this chassis. And, since the amp doesn't work now at all, I'd be guessing at what needs to be restored since it doesn't actually match anything I have on hand.
 
Tiny Daddy
I will work on all amps
Posts: 566
(3/20/04 9:05 pm)
 Re: Need some advice on "restoring" an amp
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 I would restore as-is. The only place it needs a cathode bypass cap is on the output tubes unless it's been modified for fixed bias. There's probably something simple that prevents it from working.
 
 
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