Product to secure trim pots against vibration

[ivan747]

Hi guys, Do you happen to know of a product designed or commonly accepted by the industry as a locking compound for trim pots? I have some tiny trimmers I need to fix in place. I have a product that must be baked at around 70 degrees C and is subject to vibration.

[MT]

I was to say your mom's or girlfriend nail polish is splendid. If you dont have a mom or girlfriend you go to those "1 dollar stores" and buy some cans for 2 dollar who will last a life time. The nail polish have the properties of being stiff without cracking. But i dont think it withstand baking at 70 deg, so instead you can use transformer isolation lacquer that is designed for baking process stage in rewinding transformers. This can be had for free from train/power station transformer repair shop.

[jhpadjustable]

Loctite SF 7400 is formulated for this application. You might want to ping Henkel and ask how well it stands up to a bit of heat.

[tggzzz]

Hi guys, Do you happen to know of a product designed or commonly accepted by the industry as a locking compound for trim pots? I have some tiny trimmers I need to fix in place. I have a product that must be baked at around 70 degrees C and is subject to vibration.

Even if you lock the screw of the trimpot to the housing, you still have to consider whether the contact will bounce when vibrated. If it is operating while being vibrated, that would be equivalent to introducing noise.

[JackJones]

Loctite SF 7400 is formulated for this application. You might want to ping Henkel and ask how well it stands up to a bit of heat.

It has a service temperature range of -35 to +145°C and is available in a 20 ml pack size.

The linked page says up to +145°C, should be plenty of headroom for baking at +70°C

[mzzj]

Hi guys, Do you happen to know of a product designed or commonly accepted by the industry as a locking compound for trim pots? I have some tiny trimmers I need to fix in place. I have a product that must be baked at around 70 degrees C and is subject to vibration.

Even if you lock the screw of the trimpot to the housing, you still have to consider whether the contact will bounce when vibrated. If it is operating while being vibrated, that would be equivalent to introducing noise.

Multiturn trimpots are especially suspicious as threre is considerable slop between the actuating screw and the sliding contact. Gluing the screw wont secure the internal parts against vibration.

I usually give multiturn pots couple of light taps with a small screwdriver in hopes to settle the sliding contact to ”neutral” position.

[coppercone2]

if you use threadlocker, do not use the one meant for metal.

it can make plastics brittle and mess with them, if you think you can exploit the fact that the shaft is often brass. normally for this, you can either use superglue, which is brittle, or a special threadlocker meant for plastic, which is a bit gummy that does not offer such a mechanical impedance discontinuity. as usual you need to clean everything with alcohol before use

https://www.vibra-tite.com/threadlockers/low-strength-threadlocker/vibra-tite-325-plastic-threadlocker/

The electronics product might be better because there is not much room for contact area in the potentiometer head vs a plastic bolt, so it might be formulated differently to add strength in the fillet rather in the thin contact region.

[Zero999]

I try to avoid trimpots in designs wherever possible. I prefer to connect a precision resistance box, set the value to the one which gives the best performance/correct circuit parameter and solder a suitable resistor network in place. There are also ways of achieving a similar thing which chains of resistors which can be removed by cutting the track or shorting with a jumper/solder, until the circuit works properly.

[Gyro]

I try to avoid trimpots in designs wherever possible. I prefer to connect a precision resistance box, set the value to the one which gives the best performance/correct circuit parameter and solder a suitable resistor network in place. There are also ways of achieving a similar thing which chains of resistors which can be removed by cutting the track or shorting with a jumper/solder, until the circuit works properly.

An approach illustrated nicely in the old National Semiconductor Linear Brief No 46 by Bob Pease for adjustable voltage regulators... https://www.ti.com/lit/an/snva582/snva582.pdf

[IconicPCB]

Try liquid paper

[tooki]

Try liquid paper

Correction fluid has practically zero mechanical strength. I don’t think it would help against vibration one tiny bit.