Cleaning up a Fisher 500C

Mikeorg

Active Member
I'm recaping a Fisher 500C receiver and need to know if I can use two 1000uf 50v capacitors for the large cap in the power section, I am keeping the selenium rectifier for the moment! someone replaced the large double can with junk...I don't know what was in it originally? Junk in second photo
 

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Hi Mikeorg,

Your question would probably be better served in the Fisher section. You can ask for an admin to move it if you agree.

The 1000uF caps sound way too big for the Fisher. I don't have a schematic handy, but you might be better served by keeping to the original values or a slight bump up, but not that much. Increasing the power supply caps by such a wide margin could cause problems. The guys in the Fisher area would certainly give you a more definitive answer.
 
Most of the Fishers of that vintage didn't come with a Selenium rectifier. I don't have a 400, but my other Fishers didn't originally have them.
 
Oops. That certainly does look like a Selenium rectifier in your pic. I've never had one die, but I heard they really really stink when they do.
 
That’s not the power section, it’s the negative bias supply. 10,000 is too high. Most people use two 1500uf caps there. Selenium doesn’t ‘have to’ go, but it should. It’s easy and cheap. Like my ex wife. And I don’t know what the lower blue cap in your picture is but the upper one is a Sprague atom, they aren’t junk. Try over in the Fisher section, you won’t be sorry.
 
I have a 500C that I rebuilt, The selenium provides bias for the 7591 output tubes
you risk burning them up with low bias.

As I recall bias should be -18 to -21 volts.
 
Thanks for the information RUmad I am a novice, I've gotten some Tube gear running very well but sometimes only by asking the stupid questions, I buy something find out what it was in it's original form and try to bring it back to life as it was, I will be changing out the selenium but need to learn to make a Diode rectifier first! thanks everyone!
 
Check the stickies for a reference from Mouser. When Radio Shack was alive, the go-to part was a 8A 400 component which was WAAAAyyy more than what was needed. Anything from 6A to 8A and 400+ volts would suffice. Components intended to fail in over-current situations would be placed elsewhere during a thoughtful restoration.

As to your original question, originally C-97 was a dual 1000uf 35v can. A pair of 1000uf 50v electrolytics would be perfect.
 
Thanks notdigital, I've ordered the 1000uf 50v capacitors I finally found it C-97 on my schematics, but please fill me in on as to what a package component is?
 
A bridge rectifier, a package component, is one component that is essentially four diodes in one package. Like so

CB06774A-A7F0-481F-8429-1A51F59A0617.jpeg
 
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