Sound Skulptor forums

Build help and troubleshooting => CP5176 FET compressor => Topic started by: Ewaja on December 02, 2023, 02:48:09 AM

Title: CP 5176 no output
Post by: Ewaja on December 02, 2023, 02:48:09 AM

I was done with assembling the cp5176 I had a good feeling about it, but unfortunately it didn't work as excpected.

I followed the setup guide

0V with V+ was 15.61
0V with V- was -15.61

0V with TP 7 was -5.41

i got no output when measured the 1khz sine through the XLR output, i thought i was doing something wrong.
Eventually i plugged in my MP573 and set all the MP573 settings low. On the XLR ouput i saw that the voltage in MVAC  was coming through like it supposed to be... When turning down DAW-output level the AC voltage turned down aswell.

I checked  Topic: In case your CP5176 doesn't work as expected (https://www.soundskulptor.com/forum/index.php?topic=7.0)

I've got no forgotten solder, i reflowed every joint, no reversed components or flipped ic's and everything is trimmed enough so i doesn't touch the board or ground.

I did measurement DC voltage A till G:
A=   0.0
B= -0.39
C=  0.0
D=  0.0
E=  0.0
F= -0.39
G=  0.0

ofcourse this is not how it should be.

Maybe a defective component?
Is there a short early in the circuit?
What to test?

PS. the DIY package was incomplete..  i miss one of the control knobs (on the outside of the module for:  attack, relase, ratio, input, output) i received 4 from the 5.

Title: Re: CP 5176 no output
Post by: JPK on December 02, 2023, 10:39:14 AM

Remove the DOA and check the voltages again in case the DOA is the issue.

Title: Re: CP 5176 no output
Post by: Ewaja on December 02, 2023, 01:04:11 PM

I forgot to mention. I checked without the DOA aswell

Title: Re: CP 5176 no output
Post by: Ewaja on December 02, 2023, 03:56:11 PM

Forgot to mention aswell, i think i saw some smoke coming out of c31 or c32 when trying to reach 0V to V+ / V- with the DMM. Could this be the problem?

Title: Re: CP 5176 no output
Post by: Ewaja on December 02, 2023, 09:11:32 PM

I took them out, one of the two is defect. no uprising in ohms when measuring with DMM it stays very low.
I will get another one this monday. 

Does this short have effect on other components?

Title: Re: CP 5176 no output
Post by: JPK on December 03, 2023, 08:43:58 AM

Does this short have effect on other components?
Only R56 and R57 could have been damaged.
Check they are not open circuit (no need to de-solder).

Title: Re: CP 5176 no output
Post by: Ewaja on December 05, 2023, 12:12:23 AM

replaced c31 and c32 but still no difference. i still measure the same voltages or i can say better almost nothing.
R56 and R57 are measured around 5,9 ohms inside so that should be good.
I'm no pro, but it looks like I dont have any voltage in the beginning of the scheme.

could not find a short or open circuit and don't know how search for one aswell.

Title: Re: CP 5176 no output
Post by: JPK on December 06, 2023, 03:42:39 PM

The rail voltages supply the pream via R16 (for +) and R17 (for -).
Check the solder joints on these.