[Chiller]

Hello,
today the Threshold Poti of my CP4500 stopped working. I can turn it as usual, but it has no effect on the signal. Yesterday everything was fine, so I have no idea, why it stopped working. Any solutions?
Thank you!:D

[JPK]

It could be a pot failure or a connection failure between pot and circuit.
The pot voltage can be checked on TP13 (against 0V)
Check step 1.4 here.

[Chiller]

Thanks, I've checked it, and it's just 0.45 to 0.55 VDC, when I turn the threshold. The solder points are good... is there another way to check out if it is the pot?
Thank you

[JPK]

R95-left pin should go from +12V to -12V when turning the threshold pot.

[Chiller]

Yes, that works fine. So the pot is working.

[JPK]

So the issue is around U21.
Check solder joints and values of R95...R99, U21.
Try swapping U21 with another OPA2134.

[Chiller]

Hi JPK,

I fixed it! Thank you so much for your help. I renewed all solder joints around that area but I think it was a slightly deformed pin of the U21.
Thanks again and have a good day 

[JPK]