How to Overhaul 500-C Pot

I just finished overhauling a 500C volume control/on-off switch.
It's a few hours work, but I had some issues with my left channel and traced it down to that device.

Thank you very much for this helpful tutorial, my volume/on/off control is working quite nicely now. :thmbsp:

Your instructions are spot on!
 
I'm guessing that stacked tone control pots would be similar to volume pots. Have any of you rebuilt one. I have a bass stacked pot from a 400c preamp dropping volume on the right channel. Going to look into rebuilding mine tomorrow.
 
My Fisher 400 on/off switch went broken yesterday, the internal spring part does not engage, re-install the NOS is too much after reading this thread, I found the easiest fix is just to connect the black power transformer wire to the 120v input terminal strip, it works now, but do not know if there is risk with this short cut. thanks for any advice!!
 
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This is a very interesting post. I have a 400 receiver and am experiencing a situation where the volume increase from 1 o'clock to 3 o'clock normally but does not increase at all when I turn it from 3 to 6 oclock. at 6 Oclock it increases again. Both channels increase or do not increase equally. I have tried Deoxit and there is no change. I have limited knowledge and expertise in such matters.

Do any of the knowledgable folks here think that I need to rebuild (like the photo's show) or replace the POT or could this be some other issue? Any thoughts would be appreciated
 
When the volume pot is not balanced!!

For those that have issues when detects that the volume level is not quite the same in both channels in the centralab pot used in our fisher amps this TIP will be helpfull.

When you are overhaulling the pot you need to remove the soldering shown in the red oval in both sides of the pot, at this point I detected that when you are holding the pot#1 with one hand and the pot#2 with the other hand you can twist the pot #2 a little bit (2-3 grades aprox)
So see the image:

100_4820.JPG


Hope this tip can helps!!

Regards

Luis
 
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Interesting! That would make sense...if the orientation of the two different sections where changed, meaning if they were rotated with respect to each other, it certainly could change the balance between the two.

Thanks for the tip!
 
interesting indeed. I had my volume pot rebuilt, and the problem is still there. I wasn't real thrilled about spending that bread. may try this trick.
 
After removing the 2 solder blobs and breaking the seal, does the switch portion pop off? Or do I have to remove the entire section of wiring attached to it when I pull the pot?

Also, has anybody considered using a dremel tool cut-off wheel to slice the solder joint in half?
 
Danimal

Use solder wick NOT a dremel, you must take patience, it takes a time to adjust them, and for fo this job remove the pot from the unit as show in the picture.

The most critical area is between 7:00 and 9:00 so try to equalize in this area to start to have a same level in this sector .

Regards

Regards
 
The most critical area is between 7:00 and 9:00 so try to equalize in this area to start to have a same level in this sector .

I'd say YMMV. The critical area is where you typically listen. This could vary between people, speaker efficiencies, desired volume, etc.

My 600-T on the bench with speakers borrowed from a cheap all in one is presently being run at 9:00 but if I used the inefficient, warm, Fisher XP-9 speakers, and turned it up to a slightly higher volume, I'd be at 11:00.
 
Well I spent several hours tonight taking my 400 pot out and rebuilding it. These instructions were spot on, especially the part about desoldering the switch. I soldered it back on when I was done.

The pot rotates nice and smooth now (the front support/bushing was all gummed up. I have a couple more things to check before I fire this one up, but this was something I'm glad I did.

Thank you for this tutorial!!!
 
Excellent work, I have rebuilt numerous pots that had gunk in them, as well as replacing bad power switches on these Fishers. Not sure about all the noise regarding the solder blobs, they are easily removed with a desoldering iron, followed with a little solder wick, if needed. They just pop right off and after the rebuild, which includes cleaning each track with IPA and then treating each track with deoxit on a qtip so as not to get that damn crap all over everything, and then I use a wipe of silicon grease to give the pots a nice smooth action, I use deoxit fader grease but they are all pretty much the same, this is used in Tek pots, and it don't get better than that! I also resolder the switch cover back on, that's called "doing it right". And glad to see that the indiscriminate use of deoxit is being called out, that shit can cause as many problems as it fixes, proper use is required not to screw things up with that evil stuff. Regards the reluctance to buy rebuilt or new pots at $60, if your time has no value, then do this procedure a couple of times and perhaps you will rethink your position, time consuming yes, but I do get paid to do this, although not enough...
 
Hello guys!
I'm in the club of dead Fisher switches.
Have anybody got NOS or used switch for Fisher X100b pot?
 
As much as I love taking things about could I just dunk this part into an ultrasonic cleaner and see if I accomplish the same thing? What you think?
 
So, new guy here, but decades long Fisher owner. I have a 101X that works perfect, a 400 with a trouble-some volume pot.. and an 800 C with a constant 60Hz hum. Hum's no matter where the volume pot is.
Anyway, will this mod to the pot work for my 400? I sprayed it out last week with some Deoxit and it is now worse than ever.. Any suggestions on the 800 C? Some electrolytics have been replaced as have the coupling caps from the Phase Inverter to the output valves. I used Sozo NexGen's! I replaced the main rectifier diodes with FRED diodes.
Thanks!
 
The Volume pot for the 400 is of similar construction, and the cleaning procedure is the same.

Sounds like the 800c is in need of a complete rebuild of the power supply and replacement of ALL Electrolytics at minimum. Start a new thread on each of the 400 and 800c. Take pictures of the UNDERNEATH components. Closeup's of the POWER SUPPLY and OUTPUT/P.I. Sections will help with diagnostics. If you have'nt already, build a DBT (Dim bulb Tester) with a 100W bulb. Don't plug the 800c into the wall until advised to near the end of the work.
 
Buying a soldering iron and such to attempt this this weekend! Hopefully this is the only issue my Fisher has.
 
Hey all, I have a FIsher 390 that has a problem with the right channel jumping up with a bunch of static. Here's some audio. Starts off in static, starts jumping back and forth around 11 seconds. Left channel is fine. Do you think the fix described in this thread could be an answer, or am I looking in the wrong place?
https://youtu.be/VDQCJYMlkAU
 
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