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Potentiometers: Difference between revisions
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Trying to fix the problem using epoxy (alone) is usually not effective. | Trying to fix the problem using epoxy (alone) is usually not effective. | ||
Solutions require to compress the broken plastic part in a circular fashion, either by wrapping wire or slipping a machined ring or suitable steel clamp over it. | Solutions require to compress the broken plastic part in a circular fashion, either by wrapping wire or slipping a machined ring or suitable steel clamp over it. | ||
[[User:jadney|Jim A says]]: | |||
<blockquote> | |||
The most common problem with the Tek-made VAR pots seems to be noise or intermittent connections. These can usually be overcome by simply running the pot back and forth across the bad section and thru its full range. | |||
OTOH, several of them that I've come across have suffered from broken plastic that keeps the set screw from holding tightly onto the shaft. The plastic at the center of the cruciform section is a bit too thin at the center, so it cracks there, allowing the plastic and set screw to back away from the shaft. | |||
I solved this problem by making some small aluminum rings with #4-40 tapped holes. The rings fit snugly around the cruciform section and and hold those parts together. A longer stainless set screw replaces the OE set screw and passes thru the OE threaded part of the plastic and can then be tightened against the shaft. The OD of the rings I made is about 3/4". The ID and width are made to fit the pot. For my use, I drilled and tapped two different #4-40 holes, at different offsets, so I could pick the one that was the best fit to the pot. | |||
The set screw shown in my repaired 3A8 may look like it could be shorter, but it causes no problem in this application and ensures full thread engagement in the aluminum ring. I will use a shorter set screw in the future. I think the photos show the idea pretty clearly. | |||
</blockquote> | |||
Some types that may be affected are: | Some types that may be affected are: | ||
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'''311-259''' | '''311-259''' | ||
<gallery> | <gallery> | ||
311-259 1.jpg | 311-259 in pristine condition | 311-259 1.jpg | 311-259 in [[O|Type O]], pristine condition | ||
311-259 2.jpg | | 311-259 2.jpg | | ||
311-259 3.jpg | | 311-259 3.jpg | | ||
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<gallery> | <gallery> | ||
311-116.jpg | 311-116 in [[CA|Type CA]] | 311-116.jpg | 311-116 in [[CA|Type CA]] | ||
311-116 cracked 1.jpg | close-up of cracked plastic part, | 311-116 cracked 1.jpg | close-up of cracked plastic part, crude fix using tightened wire | ||
311-116 cracked 2.jpg | 311-116 cracked 2.jpg | ||
311-116 cracked 3.jpg | 311-116 cracked 3.jpg | ||
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<gallery> | <gallery> | ||
Tek 311-0304-00 pot.jpg | 311-0304-00 pot, VAR GAIN in a 3A74 | Tek 311-0304-00 pot.jpg | 311-0304-00 pot, VAR GAIN in a 3A74 | ||
</gallery> | |||
'''Repairs''' | |||
<gallery> | |||
P3260003.JPG | Pot with Jim's repair rings | |||
P3260001.JPG | Repaired Pot in [[3A8]] | |||
</gallery> | </gallery> | ||