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 Post subject: dead spots in pots
PostPosted: Nov Fri 25, 2016 3:49 pm 
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Joined: Jan Mon 28, 2013 9:35 pm
Posts: 820
Location: Santa Rosa, CA
Here's a way to get around dead spots in pots that are often encountered in old
equipment. Especially in VOMs and VTVMs where the 'zero' pot has been
moved back and forth over a limited range so much that the carbon in the element has actually
worn away. Cleaning won't help but swapping the outer two leads (but of course
leaving the wiper contact connection alone) will move the needed adjustment point
somewhere else on the element. The down side is the adjustment will be backwards!
Steve


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 Post subject: Re: dead spots in pots
PostPosted: Nov Fri 25, 2016 6:36 pm 
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Location: Hudson, MA
You could add a resistor of one tenth the pot value to one end of the Pot. This would move the position of the pot 10% away from the dead spot and retain the adjustment direction.

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 Post subject: Re: dead spots in pots
PostPosted: Nov Fri 25, 2016 7:57 pm 
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Location: Yukon, OK USA
The throttle position sensor on my pickup just went bad this way right at cruising speed. Don't think I want to make it where I push to the floor to slow and let off to go fast!! :lol:

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 Post subject: Re: dead spots in pots
PostPosted: Nov Sat 26, 2016 2:37 am 
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black85vette wrote:
The throttle position sensor on my pickup just went bad this way right at cruising speed. Don't think I want to make it where I push to the floor to slow and let off to go fast!! :lol:


Then it becomes a clutch pedal.

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"Things are more like they are now than they ever were before" -D. Eisenhower


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 Post subject: Re: dead spots in pots
PostPosted: Nov Wed 30, 2016 2:25 am 
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Location: Fort Mohave Arizona 86426
flyboy71 wrote:
black85vette wrote:
The throttle position sensor on my pickup just went bad this way right at cruising speed. Don't think I want to make it where I push to the floor to slow and let off to go fast!! :lol:


Then it becomes a clutch pedal.


More like a suicide pedal :lol:


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 Post subject: Re: dead spots in pots
PostPosted: Mar Wed 15, 2017 11:39 pm 
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Joined: Nov Fri 10, 2006 12:24 am
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Location: Thornhill, Ontario
Try rubbing a very soft lead pencil over the dead spot on the track... worked for me once.
Cheers,
Roger

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


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 Post subject: Re: dead spots in pots
PostPosted: Mar Thu 16, 2017 7:15 pm 
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Location: Shelton, WA
A little silver paste works sometimes.

billn


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 Post subject: Re: dead spots in pots
PostPosted: Mar Sun 26, 2017 10:29 pm 
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zarco wrote:
... but swapping the outer two leads (but of course
leaving the wiper contact connection alone) will move the needed adjustment point
somewhere else on the element. The down side is the adjustment will be backwards! Steve
Screws up log pots! Try the soft lead pencil trick...
Cheers,
Roger

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


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 Post subject: Re: dead spots in pots
PostPosted: Apr Sun 02, 2017 8:47 pm 
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Sometimes you can move the wiper finger enough so that it tracks over a virgin path on the carbon element.

Pete

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 Post subject: Re: dead spots in pots
PostPosted: May Mon 29, 2017 4:49 pm 
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Location: Dallas Tx.
The graphite used to free up auto locks works good and reduces future wear.


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 Post subject: Re: dead spots in pots
PostPosted: Sep Thu 21, 2017 5:18 am 
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Peter Bertini wrote:
Sometimes you can move the wiper finger enough so that it tracks over a virgin path on the carbon element. Pete
That's OK if the bad part is still continuous (mostly it is), not if it is open.
Cheers,
Roger

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Ontario Vintage Radio Assoc. http://www.ovra.ca


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 Post subject: Re: dead spots in pots
PostPosted: Sep Thu 21, 2017 5:14 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 1922
Location: Oswego, NY, USA
Above was mentioned vehicle TPS (throttle position sensor) potentiometers, that it's not a good idea to try this repair on them. Not only that, but on our 1995 Ford Windstar minivan, when its TPS wore out; when I replaced it with a new one from RockAuto, it took the car a few drive cycles to react correctly to the new TPS potentiometer. The car did a few weird things (some potentially dangerous) before it programmed to the new TPS. So, depending on the vehicle, be careful when you change out the TPS.

Fred


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 Post subject: Re: dead spots in pots
PostPosted: Sep Fri 22, 2017 3:12 am 
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Location: Thornhill, Ontario
Fred Scoles wrote:
Above was mentioned vehicle TPS (throttle position sensor) potentiometers, that it's not a good idea to try this repair on them. Fred
Fred, you are absolutely right! Never do a kluge on a car driving or braking control. Or, indeed, any mission-critical device.
Cheers,
Roger

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


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