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Issues with a Rebuilt Champ
I recently brought a silverface champ back to life. Got him at a garage sale for free. Took the old mishapen board out, salvaged all the old carbon comps off it, bought some new sprague caps, and put them on a new board from turret boards. I also replaced the octal tube sockets that sounded like jingle bells, and the output transformer for a beefier one from Triode Elec. I rewired with some nice cloth wire, but now as I go to boot it up. I get some popping noises which tells me electricity is jumping. My guess is my preamp tube wiring , as some connections seem too close. Does this sound right? I am going to try to clean up the wiring scheme tonight. Just wanted a second opinion to reinforce my assumptions.
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Did you replace the filter cap can?
"as some connections seem too close." Usually the closest points for the preamp wiring are at the tube socket pins, is this where you mean?
Pull the 12AX7 out & power up, still popping?
Any pics of the wiring? -
I will try it without the preamp tube. What I mean is that the pins seem rather close together compared to other 9 pins I've seen. I will readjust the pins. Pull the tube and test and then get back to you.Comment
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Given that you replaced just about everything except for the filter cap can, I would suggest that as the problem. The symptom you suggested is in keeping with FC failure...but it could be a few other things. Try to rule out the obvious, as you seem to be already.
Assuming that you soldered everything carefully and nothing that shouldn't be touching, is touching (and hasen't blown your fuse or something worse by now)...the likely culprit is the 30 year old filter cap can.
Many folks say that FC's have a life span of about 10 years...probably less if the amp is not played regularly. Regardless, I think replacement is a good practice to assure that the amp is running well for the next 10 years or more.
Look at it this way, you have an amp with an apparent "weak link."
The fact that you replaced all the other parts now puts more stress on those "weak" links not addressed...especially when you play that great new amp as hard as you probably do.
Just my 2 cents!
Have fun and did I say how lucky you were to acquire that amp!MandopickerComment
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Mando, thats not even the best deal I got. I pulled a Export Model 1967 Twin Reverb off the Westside of Cleveland for $500. I mean it has the speakers and baffle replaced and some capacitors as well, and is currently having reverb and vibrato issues but still. I rebuilt the rectifier to fix the voltage issues, popped in some tungol 6l6 strs and shes a beauty now. Well at least the regular part of her. Replacing that cap can in the champ is going to be a bitch, as Fender solders the tabs directly to the chassis. Well guess thats why I bought that high powered weller for.Comment
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"Replacing that cap can in the champ is going to be a bitch," You can use individual filter caps, ground main & screen filters to a PT bolt, ground preamp filter to input jack #1. No need to even remove the cap can, unless you really want to.Comment
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Depending on the air pressure, pollution and humidity, it takes about 4,000vdc to 7,000vdc to jump a 1/16" air gap.Originally posted by womantone View Post
Not counting a weired scenario from your output transformer with no speaker load and a huge input signal, your amp might be able to muster 450vdc but only to the power tubes, not the preamp tubes.
Also, with respect to the FP style high voltage capacitor, it is fairly easy to snap those solder joints off with a chisel if you can't unsolder them with a high power heavy tipped iron.
Antique Electronic Supply sells replacement ones.
http://www.tubesandmore.com/scripts/...EE03=01_FPTYPELast edited by Bruce / Mission Amps; 08-14-2008, 05:03 PM.Comment
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I was going to suggest the chisel as well. A couple of well placed whacks and they do pop loose. Just use one you don't plan on using for fine wood work in the future.
Though, be patient when soldering the new one back into the Chassis.MandopickerComment
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