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Calling all 500C Owners!

Vinylcafe

Vinylcafe

Linvin' the Dream
I've been looking at replacing a 500C volume pot/switch with another of the same spec.
I've also been working on cleaning it up by taking it apart (thanks to Larry for his last post).
Approx 500K stereo, centre tap on both channels, turn on/off switch,
same shaft size/length, bushing size, etc.
Been doing some research and it turns out it can be done by the good folks at State Electronics who run a site called "potentiometers.com".
I have attached a .pdf document that give you the rough specs of the pot.
It's the Series K RV4; looks to be military spec ... cost $43.85
Now here's the rub, one needs to buy 30 of them !!!!
I only need one; do you think there is enough demand for this product to committ to an order that large?
Would anyone here buy one and replace their existing pot?
I might take this on if there is enough interest.
There are some details to work out (like if the "centre tap" can be moved off centre as I think the original tap is at about 145K ohms and not 250)
4-5 weeks delivery.
Is this a crazy waste of time and money?
 

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Was this pot with the exact spec used in other manufacturer's units?
I always assumed these pots were made to order for the designs in qestion.
I never even heard that they were interchangeable in 400 or 800 series tube units by Fisher.Would be great if they were!:D
 
I recently had mine rebuilt by Mark Oppat over at oldradioparts.net. real nice guy. Cost was about 50, plus about 3 bucks shipping.

I'm sure there would be some interest, but 30 is a lot of people. worth a shot though. I'll be watching the thread.
 
The HH Scott units I own have essentially the same pot except that the shaft is shorter and has a half D shape to use with a set screw. Same Fisher pot + Dremel = Scott pot.
 
Hmmmmmmmmm.......

If someone can confirm that this pot is the same as used in the 800-c, count me in; altho I'm weeks, if not months away from firing up my unit , if it'll give me a back up as well as lower the cost to you then I'm game!

At least 2 down, 28 to go?
 
The same pot was used in the 400-500B&C-800C according to my manuals. Part # 50160-104. It's possible that it was used in the 800B.

Larry
 
dsndblm said:
I'm interested. Lets see how it goes.
Click to expand...

Me too, thanks.

What about the 'Loudness terminals'?

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Vinylcafe said:
I've been looking at replacing a 500C volume pot/switch with another of the same spec.
I've also been working on cleaning it up by taking it apart (thanks to Larry for his last post).
Approx 500K stereo, centre tap on both channels, turn on/off switch,
same shaft size/length, bushing size, etc.
Been doing some research and it turns out it can be done by the good folks at State Electronics who run a site called "potentiometers.com".
I have attached a .pdf document that give you the rough specs of the pot.
It's the Series K RV4; looks to be military spec ... cost $43.85
Now here's the rub, one needs to buy 30 of them !!!!
I only need one; do you think there is enough demand for this product to committ to an order that large?
Would anyone here buy one and replace their existing pot?
I might take this on if there is enough interest.
There are some details to work out (like if the "centre tap" can be moved off centre as I think the original tap is at about 145K ohms and not 250)
4-5 weeks delivery.
Is this a crazy waste of time and money?
Click to expand...

Actually, I think we'd need 2RV7-KK commercial series as the RV4 series is monophonic (single-element only)...probably KKWSA5031F(???) - not sure of the shaft length off the top of my head. I'd be interested if the price is around $43 for the 2RV7-KK-series.

-D
 
It would have to be a KKK as the switch would be the third section. KKKWSA5031F48. The shaft on mine is 1-1/2" from the start of the threads at the base to the end of the shaft. I get this feeling it's gonna be considerably more than $43. and change.
Like maybe double or a bit more.

re: Loudness tap mine meters out between 150 and 160 oHms depending on which side I check. So it's roughly 1/3 of the control. EDIT 5-9-12 D'OH!!! I mean 150K to 160K.

Larry
 
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larryderouin said:
It would have to be a KKK as the switch would be the third section. KKKWSA5031F48. The shaft on mine is 1-1/2" from the start of the threads at the base to the end of the shaft. I get this feeling it's gonna be considerably more than $43. and change.
Like maybe double or a bit more.

re: Loudness tap mine meters out between 150 and 160 oHms depending on which side I check. So it's roughly 1/3 of the control.

Larry
Click to expand...

Good point about the switch counting as a section. I still might be interested if it was around $60 or so. It's a PITA to turn my Fisher on and off at the wall via a switchable outlet adapter.

-D
 
bhamham said:
Me too, thanks.

What about the 'Loudness terminals'?

attachment.php
Click to expand...

The loudness terminals would be accomodated by a "center tap" that is accomodated by the price. I never asked the rep if they can accomodate an "off center tap". For the loudness to work properly I'm assuming this tap would have to be around 140-150K ohms, which his where mine measures out.
As for the type of model required, I never really did go through the other pots in the brochure, I simply described to them the basic functins required and was told that it was the KV4 that could acccomodate.

Are there resons to believe that this model would not do the trick, I did see the right bushings, shaft length, flat tipped shaft, and switch configuration.
 
larryderouin said:
It would have to be a KKK as the switch would be the third section. KKKWSA5031F48. The shaft on mine is 1-1/2" from the start of the threads at the base to the end of the shaft. I get this feeling it's gonna be considerably more than $43. and change.
Like maybe double or a bit more.

re: Loudness tap mine meters out between 150 and 160 oHms depending on which side I check. So it's roughly 1/3 of the control.

Larry
Click to expand...

Larry,

I will put it to him with the model number as you described. I will also ask about a centre tap at 150 ohm position.
I will keep everyone posted.
I'm out of town for work until Friday night, so might not have an answer for you until them.
But I am on it. Let's see where this goes.
 
Vinylcafe said:
The loudness terminals would be accomodated by a "center tap" that is accomodated by the price. I never asked the rep if they can accomodate an "off center tap". For the loudness to work properly I'm assuming this tap would have to be around 140-150K ohms, which his where mine measures out.
As for the type of model required, I never really did go through the other pots in the brochure, I simply described to them the basic functins required and was told that it was the KV4 that could acccomodate.

Are there resons to believe that this model would not do the trick, I did see the right bushings, shaft length, flat tipped shaft, and switch configuration.
Click to expand...

The problem with the KV4 is that it is a single-channel pot - it would not work for stereo.

-D
 
There have been references in this thread to the loudness tap being both approximately 150 ohms, and approximately 140,000-150,000 ohms.

Make sure you state it correctly if you have this custom made.
 
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