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800C Volume Pot problem.

larryderouin

larryderouin

I'm VERTICAL and Breathing...most of the time.
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My 800C developed late this afternoon. The volume was lower on the Left side, with the Balance pot centered. Problem was traced down to a Volume pot problem. The Left side has developed a 30-40KoHm difference across the board when testing the pots with a meter. The difference is enough to cause me to have to balance the sound by turning the Balance pot to 9:00 position.

I noticed the switch was acting up the other day, so I hit it and the pot with DeOxit D-5, then Gold for the pot. Since then the pot has been asymptomatic. But a new one is in the future.

Other than EBAY, is there a distributor that would have this pot new or a functional equivalent. 500K DUAL Volume with a loudness tap, 1-1/2" shaft from base of the threads to the end, and a 1/2 cut the last 1/2". The 400 has the same pot as would the 500C.

I thought the pot from the 65 Ambassador would physically fit, but the shaft is too short. Different pot construction also. Electrically it would work. None of my SS Receivers has a compatible either.

Any help appreciated.

Larry
 
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Hi Larry,
There tough to find, I found two on ebay awhile back there a dual 500K pot with
a loudness tap, but no switch had to add a switch to the back of the amps, there ok
but better is needed, there is also a guy on ebay who sells a Alps with a loudness
tap that what I'm using in my X100, but then again no switch, and I've seen some
NOS CTS that's for the Fisher for $50.00, but Have to add a extension to the shaft,
which would work you can try that out but again it's on ebay.

Tube
 
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larryderouin said:
My 800C developed late this afternoon. The volume was lower on the Left side, with the Balance pot centered. Problem was traced down to a Volume pot problem. The Left side has developed a 30-40KoHm difference across the board when testing the pots with a meter. The difference is enough to cause me to have to balance the sound by turning the Balance pot to 9:00 position.

I noticed the switch was acting up the other day, so I hit it and the pot with DeOxit D-5, then Gold for the pot. Since then the pot has been asymptomatic. But a new one is in the future.

Other than EBAY, is there a distributor that would have this pot new or a functional equivalent. 500K DUAL Volume with a loudness tap, 1-1/2" shaft from base of the threads to the end, and a 1/2 cut the last 1/2". The 400 has the same pot as would the 500C.

I thought the pot from the 65 Ambassador would physically fit, but the shaft is too short. Different pot construction also. Electrically it would work. None of my SS Receivers has a compatible either.

Any help appreciated.

Larry
Click to expand...

Where do you want the tap?
I had the same search problem but mine was even better, a 1 Meg with a contour tap.
AES can supply that one. OK balance wise but nothing to write home about.
I'll see what I can find.
Contact these guys and see if they'll sample you one:
http://www.potentiometers.com/pdf/BITC_P270.pdf
 
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Clean&Tight said:
Where do you want the tap?
I had the same search problem but mine was even better, a 1 Meg with a contour tap.
AES can supply that one. OK balance wise but nothing to write home about.
I'll see what I can find.
Contact these guys and see if they'll sample you one:
http://www.potentiometers.com/pdf/BITC_P270.pdf
Click to expand...

Hi,
That may be good, still lose the switch and loudness tap, but you can try
them, I called them once and they like a large order, singles are high.
Maybe a bunch of us can get together and design a new type of pot from them and put a large order in.

Tube
 
I think at this point I'd rather a parts donor pot. There isn't a lot of anything that I could find out there that's new that looks like the pot. I've got 1 or 2 sources looking for donor pots.

thanks guys.

Larry
 
Larry,
I pulled out the pots, but it was too late to go get a 500-C to see if it should be the short shaft or long shaft part. Will try again tonight.
 
I've opened it up, and examined it under a magnifier. Can't find anything visually wrong with the pots. But there is a definate 30-40K differential betweeen sides. I readjusted the wipers to get slightly more tension, it didn't help. It felt sloppy in the first place, so it could be that it's just worn out.

Thanks Don. Tubes are packed in case you find one.
Larry
 
Hi Larry,
There old and I have done the same thing, took them apart and clean relube
them and there still bad, I'm experimenting with a new pot I had, it's a Alps Blue
velvet, but it's a 250K trying it out let you know how it make out later.

Tube
 
larryderouin said:
I've opened it up, and examined it under a magnifier. Can't find anything visually wrong with the pots. But there is a definate 30-40K differential betweeen sides. I readjusted the wipers to get slightly more tension, it didn't help. It felt sloppy in the first place, so it could be that it's just worn out.

Thanks Don. Tubes are packed in case you find one.
Larry
Click to expand...

Oh man, I hope you get to the bottom of this. I have the same problem with the same channel. (diff fisher unit)
It will only balance out when the volume control is at 75% or higher.I have a parts donor, but I don't want to do unnecessary surgery.



Please update your progress and good luck.


Steve
 
not sure but i think resistance paint is available to repair the tracks in pots. i was looking in to it a few years ago but found the correct pot. unless they are wire wound of course
 
Hi,
I'm feeling better now, I thought it was me and not my stereo, now I know others
having problem too, we have to get this problem fixed, so we can all go back and listen to music.

Tube
 
tube-a-lou said:
Hi,
That may be good, still lose the switch and loudness tap, but you can try
them, I called them once and they like a large order, singles are high.
Maybe a bunch of us can get together and design a new type of pot from them and put a large order in.

Tube
Click to expand...

I'd be up for a group buy on that...

-D
 
Hi all,

Volume pot update;

I took out the NOS Centralab dual 500K pot today and tested it
with a ohm meter, and the readings were 516 on the right and 528
on the left. Now your most likely going to hear that difference, so I
put in a Alps Blue Velvet pot that I had, but first tested it, it's way closer
503 and 504, that's what 1% off. So I put it in and disconnected the loudness
control (don't use it any way), hooked it all up and wait for it. Wow that's
better, sound dead center, wide stereo separation, highs that I always
had a problem with in both speakers back in all it's glory, it's really better,
So in the end the original stuff is getting old, and I want to enjoy listening
to the music, so guy's listen just modify them a little, I left all the wiring
in so if I come across a 4 tap volume pot which I will continue to search
for, I can have the loudness control back in, there must be one someplace.
I know I know you want to keep it original but if that is going to get
in the way of the music, what's the point just get to it and enjoy.:banana::thmbsp:

Tube
 
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I metered mine when it was out and the Right was 486K and the left was 440K across the outer pins. At the loudness tap from 0 it was 110 on left and 75 on right.

I also checked my 400. 490 and 506.

Larry
 
larryderouin said:
I metered mine when it was out and the Right was 486K and the left was 440K across the outer pins. At the loudness tap from 0 it was 110 on left and 75 on right.

I also checked my 400. 490 and 506.

Larry
Click to expand...

Hi Larry,
Wow that's a big difference there, that's why I'm starting to use
the Alps Blue Velvet's there like 3% off each side and you can
hear the difference. I know people like to keep it vintage but
when the old parts start to fail what are you going to do.

Tube
 
I have a 500-S with the same symptoms, but I'm resigned to even out the output with the balance control. After all, it's simple to compensate for. I'd rather keep the original controls and utilize the loudness contour circuit when appropriate. I went to great efforts to replace the A/C switch on this bugger just a month ago. At this point, I'm happy to be able to switch the old girl on and off!
 
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