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Author Topic: Hold a trimpot in place  (Read 6168 times)

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Offline nemo000111

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Hold a trimpot in place
« on: October 19, 2013, 05:13:08 AM »
I need to be able to fix a trimpot in place.  After applying a reasonable amount of force, the compound should shear allowing the dial to turn.  I was thinking of something along the lines of nail polish, but wasn't sure if it'd be too weak.  The goal of this is to have it not move during normal use and not as a tamper indicator.  Any suggestions would me much appreciated.  Thanks.
« Last Edit: October 19, 2013, 05:27:46 AM by nemo000111 »
 

Online ThomasDK

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Re: Hold a trimpot in place
« Reply #1 on: October 19, 2013, 07:47:07 AM »
Tamper laquer.

Great stuff, looks like nail polish, but will let you retrim for several hours before it hardens.
 

Offline David_AVD

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Re: Hold a trimpot in place
« Reply #2 on: October 19, 2013, 08:53:32 AM »
Cheap: nail polish

More expensive: Loctite (maybe one of the lower strength threadlocker types)
 

Offline philpem

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Re: Hold a trimpot in place
« Reply #3 on: October 19, 2013, 11:23:42 AM »
Cheap: nail polish

More expensive: Loctite (maybe one of the lower strength threadlocker types)

Somewhere in the middle: "Bloc'lube" (BLR) by Electrolube: http://www.electrolube.com/docs/maintenancemain.asp?id=148
I don't use it often, but that's the stuff I use. I've also (ab)used it as a varnish for ferrite rod antenna coils, but I try not to make a habit of that...
Phil / M0OFX -- Electronics/Software Engineer
"Why do I have a room full of test gear? Why, it saves on the heating bill!"
 

Offline mjrandle

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Re: Hold a trimpot in place
« Reply #4 on: October 19, 2013, 11:33:29 AM »
SentrySeal, blue stuff is also better known as Smurf Poo ;)
 

Offline Stonent

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Re: Hold a trimpot in place
« Reply #5 on: October 19, 2013, 01:49:46 PM »
I seem to remember as a kid, a lot of transistor radios had the RF section with trimmers, chokes and variable-caps dunked in wax or what felt like wax. Yuck.

I tend to see blue Loctite style stuff used a lot.
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Offline Rerouter

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Re: Hold a trimpot in place
« Reply #6 on: October 19, 2013, 04:26:52 PM »
cheap red nail polish at my work, one of the more pricy ones we tried had a very fine glitter that made it have a resistance close to 10K per cm which became a very big problem later on
 

Offline David_AVD

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Re: Hold a trimpot in place
« Reply #7 on: October 19, 2013, 04:56:29 PM »
cheap red nail polish at my work, one of the more pricy ones we tried had a very fine glitter that made it have a resistance close to 10K per cm which became a very big problem later on

Did it look fabulous on your nails though?   :-DD
 

Offline Rerouter

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Re: Hold a trimpot in place
« Reply #8 on: October 19, 2013, 08:16:36 PM »
Well how else do you test it?  ::)
 

Offline David_AVD

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Re: Hold a trimpot in place
« Reply #9 on: October 19, 2013, 10:11:01 PM »
touché
 

Offline GK

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Re: Hold a trimpot in place
« Reply #10 on: October 19, 2013, 10:41:01 PM »
Nail polish is ideal as it has a thick consistency and won't run where you don't want it to go, unlike something like Loctite threadlocker or similar that has almost water-like viscosity.

If you don't like the idea of having something girly like nail polish on the bench, you can buy the stuff with a more respectable label. This is what I use:

http://australia.rs-online.com/web/p/epoxy-coatings/1965245/

It's bottled like nail polish and smells exactly the same.
« Last Edit: October 19, 2013, 10:43:06 PM by GK »
 

Offline SeanB

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Re: Hold a trimpot in place
« Reply #11 on: October 19, 2013, 10:55:14 PM »
Nice thing with nail polish is you can get different colours to use for different pots, so you can adjust, lock and next time use a different colour so you know which ones have been adjusted. As well it is available in a clear version so you can use it to lock panel screws so they will not come loose while being close to invisible.
 

Offline Capital

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Re: Hold a trimpot in place
« Reply #12 on: October 21, 2013, 12:42:40 AM »
HOT MELT GLUE- it will hold the pot and can be easily removed by peeling. Its just low temp polyethylene so it does not bond very well.
 

Offline Mechatrommer

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Re: Hold a trimpot in place
« Reply #13 on: October 21, 2013, 06:30:15 AM »
dont take your wife's nail polish if she is an active forumer.
if something can select, how cant it be intelligent? if something is intelligent, how cant it exist?
 

Offline peteroakes

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Re: Hold a trimpot in place
« Reply #14 on: October 21, 2013, 09:33:11 AM »
whatever you choose, it needs to dry brittle and should not be runny when first applied, I find superglue and the likes way to runny and it can easily work into the mechanics of not careful and permanently cease it so I avoid it. Similarly liquid tape used to waterproof crimp connectors etc. would work but may be too flexible for your purposes causing rebound while trying to fine adjust rather than cracking

I would agree with the many forum reply's, Nail polish is a good and cheap choice, and you can even pick a favorite color lol. it dries brittle so when you need to re-adjust it will crack and not cause any springiness to the adjusting.

Lock tight is a good choice too but more expensive than cheap nail polish and available in less colors
 

Offline karchiba

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Re: Hold a trimpot in place
« Reply #15 on: October 25, 2013, 06:25:01 AM »
There's an enamel-like product called "Glyptal" (GE made it) that was used to coat transformer windings, that works well for locking trimmers.
 


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