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CP5176 FET compressor / My CP 5176 is very quiet on the input stage
« Last post by Denis on March 03, 2026, 06:25:40 PM »Hi guys
one of my 2 5176 is very quiet. it is right behind my 573 and if i crank the gain up around +20db in comparison to my working 5176 it sounds as the other.
I think either Q1 or Q2 is having an issue but Id like to hear from someone who knows what is going on
When I use line level 100mVAC to calibrate even at max input and max output it almost does not compress where the working one compresses.
Here my measurements:
DC: everything is fine. the "broken" unit and the working one are the same. Resister values are fine. Specifically all around Q1 are fine. C3 C4 and C7 seemed to be fine. I measured C7 and both fine. I could not measure C3 and C4 but resistance is the same on both units.
AC:here are some differences.
When I the same signal on both units, lets say the calibration 100mVAC I have at tp1 around 60mVAC on both. I have good signal on tp2, I think it was .5mVAC or something but on the broken one it was way less. something around 10mVAC+-.
I checked around Q1 and I have looking at the round side from left to right measured to 0V 60mVAC, 30mVAC and 45mVAC. on the broken one it is 0.0mVAC 0.0mVAC and 25mVAC.
It was working at some point. I dont know what happend. No damage is noticeable. Anything else I can measure to find the broken part?
I would just replace Q1 but I found that the BF245 has different pin outs? I found 2 different variants called the same. Or is it maybe some different part?
EDIT:
On the working unit I have with 60mVAC on tp1 and output at 100% I have 1.1VAC on tp2, on the broken unit I have 14mVAC on tp2
Thanks a lot!
Denis
one of my 2 5176 is very quiet. it is right behind my 573 and if i crank the gain up around +20db in comparison to my working 5176 it sounds as the other.
I think either Q1 or Q2 is having an issue but Id like to hear from someone who knows what is going on
When I use line level 100mVAC to calibrate even at max input and max output it almost does not compress where the working one compresses.Here my measurements:
DC: everything is fine. the "broken" unit and the working one are the same. Resister values are fine. Specifically all around Q1 are fine. C3 C4 and C7 seemed to be fine. I measured C7 and both fine. I could not measure C3 and C4 but resistance is the same on both units.
AC:here are some differences.
When I the same signal on both units, lets say the calibration 100mVAC I have at tp1 around 60mVAC on both. I have good signal on tp2, I think it was .5mVAC or something but on the broken one it was way less. something around 10mVAC+-.
I checked around Q1 and I have looking at the round side from left to right measured to 0V 60mVAC, 30mVAC and 45mVAC. on the broken one it is 0.0mVAC 0.0mVAC and 25mVAC.
It was working at some point. I dont know what happend. No damage is noticeable. Anything else I can measure to find the broken part?
I would just replace Q1 but I found that the BF245 has different pin outs? I found 2 different variants called the same. Or is it maybe some different part?
EDIT:
On the working unit I have with 60mVAC on tp1 and output at 100% I have 1.1VAC on tp2, on the broken unit I have 14mVAC on tp2
Thanks a lot!
Denis