Bought a Fisher 500C tube. Now what??

riglehart

Was parusing the paper this weekend and found a Fisher 500C for $50. I know nothing about tube amps and did a little research and found these go for a few hundred on ebay and get decent reviews. So, I went and got it.

Everything seems to work fine so far. It drives my polk 11T just fine.

I'd like to tinker on this. I have a EEE degree, but no practical experience in electronics (I'm a computer SW person since 1990). So, I probably know/remember enough to be dangerous. Here's a few quick questions...

1) What works good to clean the grey film off the metal chassis?
2) The volume knob is staticky. Channels cut out in certain spots. Does it just need a good cleaning? What's the stuff I hear people talk about to clean out the pots?
3) Anyone know if/how the bias needs to be adjusted? The prior owner bought it new and said he had changed "a couple" tubes in it.
4) Should I bother getting new tubes? There are at least 17 tubes on this thing.
5) Why are some of the tubes covered with little round metal things?

I have a Jolida 202 in the mail that I bought from dorokusai, but $50 seemed like a pretty cheap adventure.

halo

Caig products work well for cleaning contacts & noisy pots. LINK

fredv

riglehart wrote:

Was parusing the paper this weekend and found a Fisher 500C for $50. I know nothing about tube amps and did a little research and found these go for a few hundred on ebay and get decent reviews. So, I went and got it.

Everything seems to work fine so far. It drives my polk 11T just fine.

Congrat, this is a steal!!!

I'd like to tinker on this. I have a EEE degree, but no practical experience in electronics (I'm a computer SW person since 1990). So, I probably know/remember enough to be dangerous.

Yes, indeed but many are common sense of electricity. I am a SW from college to now and only started learning restoring vintage gears last year.
I am sure you can do it!! There is fisher user groups at yahoo groups.
There is a lot of vintage knowledge there.

Here's a few quick questions...
1) What works good to clean the grey film off the metal chassis?
2) The volume knob is staticky. Channels cut out in certain spots. Does it just need a good cleaning? What's the stuff I hear people talk about to clean out the pots?
3) Anyone know if/how the bias needs to be adjusted? The prior owner bought it new and said he had changed "a couple" tubes in it.
4) Should I bother getting new tubes? There are at least 17 tubes on this thing.
5) Why are some of the tubes covered with little round metal things?

I have a Jolida 202 in the mail that I bought from dorokusai, but $50 seemed like a pretty cheap adventure.

1. It is very difficult to remove the oxidized surface, try Nevr-Dull.
2. CAIG,DeOxit.
3. I am not familiy to this model. My fisher has cathode bias (sometimes also called auto bias) that doesn't need adjustment. Look at the chasis to see there are place to insert probes and pot for adjustment. If you don't find anything like that, then it is very that it is aut bias.
4. The small tubes (tuner and preamp) typically last a lot longer than the output tubes (the 4 big tubes a the back, I think they are 7591's). Check the brands of the tubes, if they are fisher then they are problably original. Unless they are bad, keep them. If they are good, they are worth more than you paid for the whole thing Also, look at the small tubes (12AX7), if they are fisher brands, then there is a good chance that they are telefunken, meaning another fortune
5. The round metal cover are tube shield to avoid interference.

Have fun!!!

ESavinon

Here's a site that specialize in restoring old fisher audio.
http://www.fisherdoctor.com/

riglehart

ESAVINON wrote:

Here's a site that specialize in restoring old fisher audio.

I ran across those guys a couple days ago. I think they also sell a kit that has all the critical parts for a do-it-yourself job, too. I might try that. I have a feeling I'm going to have to learn how to solder better.