Tube Amps / Music Electronics
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The sunn still shines online!
|3/13/2000 8:30 PM|
||Re: Very old Fender Deluxe, any advice?|
>>(I *think* 5C3?)
I think that is the version that I'm working on.
I was looking in a old groovetubes book that I've had for years & I think that is it. Based on the tubes it has anyway.
This isn't mine I'm just fixin' it up as a favor.
Plus, I love doing that kind of stuff.
I know she won't be using any fx's.
|3/13/2000 9:17 PM|
Does the amp have 6SC7 or 12AY7 preamp tubes - the 1954 model had 12AY7s with metal inserts to adapt the octal (6SC7) holes for 9-pin sockets. It also listed 6SC7s on the tube charts. Sort of a "5D3." You can date the amp using the codes on various parts like potentiometers - specific info is listed at Duncan's site and others.
|3/14/2000 1:25 PM|
It has 2 6SC7's. I have an old GrooveTubes book & this version isn't listed.
Thanks for heads-up at the Duncan site.
|3/13/2000 9:20 PM|
[I *think* 5C3?)
I think that is the version that I'm working on.]
That's one of my favorites. I would leave the input circuit exactly the way it was designed and just don't plug anything into it that makes the amp sound bad. I had one like that and never had any problems with the input circuit at all. My preference for resistors is carbon-film for stability but carbon comps were stock in that amp so use them if that's important to you. I use 1W or 2W resistors to maintain that "big" resistor look. The original resistors were 1/2W but were much larger than todays 1/2W's. It's hard to find modern 1/2W's with leads long enough to reach across the eyelet board. I also used 630V metal-polyester axial lead coupling caps from Antique Electronic Supply to replace the coupling caps. They sit better than Sprague Orange Drops in a Tweed Fender and sound fine to my ear. Of course anything will sound better than an old leaky one. Most people will steer you toward the Orange-Drops. They are fine caps too - I just don't have an opinion yet if they sound "better" than available axial lead film type coupling caps. I will tell you this - Orange drops are more prone to microphonics than the film caps I've used. This is especially noticable on the input caps of a 5C3.
This is a great amp when it's working properly. The 5C3 used 6SC7 preamp tubes. Get 6SC7GT's (Glass Tubes)to replace the metal ones.
|3/14/2000 1:33 PM|
Last nite I measured all of the resistors & they were all fine, so I won't replace them. Except I wasn't able to check the 2 5Mohm, my DVM won't go that high. I'm gonna leave them in there until I get the caps replaced & see.
It has 1 metal & 1 glass 6SC7. I swapped them around & didn't have any change in performance. Depending on how much the owner wants to spend, they might not get replaced.
One thing that I saw last nite when I had it all opened up, is that the speaker has 4 leads & a transformer mounted on it.
all 4 wires go the the transformer & from there 2 go to the speaker itself.
Does the power section put out ac?
|3/14/2000 4:36 PM|
Sounds like you've got an early one all right. It used to be common to mount the output transformer on the speaker but not in some time. Now you say that four leads go to the transformer? One of these is the B+ transformer center tap, two are plate leads for the 6V6s and the other is probably a ground? Carefully check the insulation on these leads - if it's cracked or chafed a B+ to ground short may occur. If you get a chance please read all of the numbers from a couple of your potentiometers and post them here - we wanna know when the thang was made.
|3/14/2000 4:43 PM|
It sounds like the output transformer is mounted on the speaker instead of on the chassis. My guess is that the four leads going from the chassis to the OT consist of: one each for the 6V6 plates, one for the main B+/secondary center tap, and a ground wire to ground the transformer and speaker (mostly for safety reasons).
All audio power amps put out an AC signal.
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