How fragile are trimmer resistor??

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Deepdark

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Hi. As the title said, how fragile are they? Let me explain. I was playing in my LA2A with R37 and R3, to test their effects on compression and signal. I know I made a lot of turn, in every way possible to test them in real time, and I think I probably turn up to much, I didn't get any more compression. I replace T4B with another one I had, change V4, in case it would have been a meter trouble, take all voltages, everything was allright. Then,  I put a ohm-meter to check out the 2 trimmer and no matter how much I turn, in which way I turn, the actual resistance increase or decrease no more. So I probably have broken something inside them. So, I guess my trouble lies there.
 
Deepdark said:
Hi. As the title said, how fragile are they? Let me explain. I was playing in my LA2A with R37 and R3, to test their effects on compression and signal. I know I made a lot of turn, in every way possible to test them in real time, and I think I probably turn up to much, I didn't get any more compression. I replace T4B with another one I had, change V4, in case it would have been a meter trouble, take all voltages, everything was allright. Then,  I put a ohm-meter to check out the 2 trimmer and no matter how much I turn, in which way I turn, the actual resistance increase or decrease no more. So I probably have broken something inside them. So, I guess my trouble lies there.

i always overturn them ( hearing that clicking noise ) 
past zillion years, none got broken doing that...
my guess is, it must be the current going through them!


 
current is pretty small inside an LA2A. I completly removed them, and test them and they just don't work. I turn a lot of time and don't hear the little clic, too
 
they must be dead :(

get a new pair!

i am surprised that u killed them tho... i never had the privilege of  killing them, by over turning them  :(

 
yeah that's what i'll do. I'm surprise, too. Since we're not talking about big current, nor voltage. Maybe by over turning them from one extreme to another, a lot of time they had broken, I don't know
 
and since it was compressing well until the moment I decided to re-check the calibration and turn both trimmer, it lead me to thinks that it's the only possible culprit. There is no change in the make up gain section. The unit is still as silent as it was in term of noise, it passes audio as fine as it did, it's really the only trouble that appeared when turning again these trimmer. I can still adjust the 0 on the meter, so this trimmer work and I checked with a ohm-meter and it works perfectly, change resistor value like a charm.
 
haha I guess so. I made a little research and it looks to not be uncommon to see broken trimmer. Maybe a bad or more fragile batch, who know
 
There are lots of different kinds of trim pots, but in general they are not very robust, and not intended to be tweaked many times. Also be careful about using heavy, too large screw drivers

Multi-turn trim pots are more robust, more expensive, but have different foot prints.

JR
 
JohnRoberts said:
There are lots of different kinds of trim pots, but in general they are not very robust, and not intended to be tweaked many times. Also be careful about using heavy, too large screw drivers

Multi-turn trim pots are more robust, more expensive, but have different foot prints.

JR

Thanks John. That's what I noticed. I used little cheap 2$ multiturn trimpot, and play a lot with them to measure the effects of them, and basically, they cease to work (cease to increase or decrease resistance) and the unit stopped to compress, so probably R3 is set for maximum resistance between pin 3 and 2 so signal is shorted to ground, thus no compression occur. Same with R37, the pot is max resistance between pin 1 and 2, so I'm probably passing all my signal through C12 and get a HPF
 
Also make sure you know which pins which.  You might be connecting across the main element of the pot and not the center trim pin in which case you make adjustments but the center tap is not connected to the correct pin on the PCB.    I've been fooled before with assuming I understand the hookup and found out the center tap was on another pin.  Just a thought.
 
Thanks. I just changed them and it works now. Since they are linear, i would have to turn from one side or another to adjust it. But i ynderstand what you Say. They are in th side chaun circuit of the la2a. One adjust the response and the other, when fully ccw (assuming it is installed correctly) will short the grid of v4 to gnd, so will no compress. If installed backward, then we have to turn the other way. Anyway, now it works and i learned that they are not intended to be abused hahaha
 
Deepdark said:
I used little cheap 2$ multiturn trimpot,

I had some multiturn trimpots fail from use but it was not because of the resistive track inside it was always because of the legs being fragile and the legs wires break easily were they meet the plastic body of the trimpot
 

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