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 Post subject: Sudoku fixes dead potentiometer!
PostPosted: Jan Sat 23, 2016 6:30 am 
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Joined: Nov Fri 10, 2006 12:24 am
Posts: 2359
Location: Thornhill, Ontario, Canada
A bizarre story...
I have an Stark model SAG-2 audio signal generator that had a faulty output level potentiometer - a 5K linear (but no schematic!) Unfortunately, the pot is concentric with a decade switch for output level switching, so it's custom - no easy replacement with a generic pot unless I put a new hole in the cabinet for it. I tried cleaning it with iso-propyl alcohol to no effect.
I took it out and popped the back off. There was a complete track-break near one termination, about 1/8 inch long. Looked like a new hole was going to be needed in the case! But...
My wife likes doing Sudoku puzzles. This involves writing numbers in squares until the puzzle works out... lots of erasing and re-entering them. HB pencils (all we had in the office) are too hard, not easily erased. A while back we were in Staples looking for 2B or softer pencils... hard to find, shelves full of Chinese HB's. Finally she found a couple of 2B's at about 5 times the price of HB's, so bought them.
Now, we've all heard of repairing minor potentiometer track damage with soft lead pencil marks... and now I knew where there was a 2B pencil! Would this idea work to bridge 1/8 inch of completely missing carbon track? I put several layers of 2B pencil marks across the gap, sort of building up the carbon in layers. It worked! Pot now reads 4.6K, close enough... but would it last with the slider going over it? Well, so far, yes, but I keep the pot at mid-track most of the time.
So, Sudoku fixed my pot, for now... sort of. We'll see how long it lasts.
Cheers,
Roger

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Roger Jones,
Thornhill, Ontario
Ontario Vintage Radio Assoc. http://www.ovra.ca


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 Post subject: Re: Sudoku fixes dead potentiometer!
PostPosted: Jan Sat 23, 2016 8:03 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 32348
Location: SoCal, 91387
Congrats on the fix, but you know it won't last forever.

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\\\\\\\\\\\\\\\\\\\\\\\\He Who Dies With The Most Radios Wins//////////////////


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 Post subject: Re: Sudoku fixes dead potentiometer!
PostPosted: Jan Sat 23, 2016 2:37 pm 
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Joined: Mar Sat 14, 2009 5:56 pm
Posts: 4394
Location: VA 22602
Keep a sharpened back-up pencil in your Stark cabinet.

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I'm not a hoarder, I'm a caretaker of scarce commodities


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 Post subject: Re: Sudoku fixes dead potentiometer!
PostPosted: Jan Sat 23, 2016 4:01 pm 
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Joined: Jun Sat 18, 2011 3:36 am
Posts: 2288
Location: Milton, FL 32570
fifties wrote:
Congrats on the fix, but you know it won't last forever.

But neither will he or the radio so it's a win situation.

jason

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Thanks,
Jason
KN4UCQ


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 Post subject: Re: Sudoku fixes dead potentiometer!
PostPosted: Jan Tue 26, 2016 12:04 am 
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Joined: Feb Thu 08, 2007 12:36 am
Posts: 2139
Location: Hillsboro, Oregon
Worth it just for the giggle factor.


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 Post subject: Re: Sudoku fixes dead potentiometer!
PostPosted: Jan Tue 26, 2016 8:13 pm 
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Joined: Mar Tue 03, 2009 11:12 pm
Posts: 1512
Location: Hutchinson KS
I have tried using remote control button repair kits in similar situations, works great. It looks like a tar that is applied to the rubber buttons on remote controls that wear out. Might even be aquadag coating for all I know!


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 Post subject: Re: Sudoku fixes dead potentiometer!
PostPosted: Apr Tue 12, 2016 7:16 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 5722
Location: 253 Blanche St. Plymouth, MI USA
The 'pencil lead" repair will not last. I can repair or duplicate most any control. Concentric shaft types even.
Mark Oppat
Plymouth, MI
*****


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 Post subject: Re: Sudoku fixes dead potentiometer!
PostPosted: Apr Tue 12, 2016 11:23 am 
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Joined: Jul Mon 26, 2010 8:30 pm
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Location: Annapolis, MD
I bought some conductive paint some time ago.....will eventually be trying it.

In principle, one should be able to recreate the process used to make these things, but---as long as you can get the parts from someone like Mark Oppat---it may not be worth the effort.

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"Measure voltage, but THINK current." --anon.


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 Post subject: Re: Sudoku fixes dead potentiometer!
PostPosted: Apr Fri 15, 2016 11:37 pm 
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Joined: Nov Fri 10, 2006 12:24 am
Posts: 2359
Location: Thornhill, Ontario, Canada
pixellany wrote:
... but---as long as you can get the parts from someone like Mark Oppat---it may not be worth the effort.
Agree, but I had it back up and running in 20 minutes! I know it won't last. Use the soft pencil... order a replacement pot!
Cheers.
Roger

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Roger Jones,
Thornhill, Ontario
Ontario Vintage Radio Assoc. http://www.ovra.ca


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