Sound Skulptor forums
Build help and troubleshooting => CP5176 FET compressor => Topic started by: macguy78 on March 28, 2022, 07:25:18 AM
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I’ve gotten to the setup stage and I have a few questions:
I have a single mono module; are steps 7 and 8 necessary?
Also, does the compressor need to be engaged at this step? Without it on, I can get to the 13.5VAC needed. With it on, the highest reading I’ve been able to get is 1.550VAC.
I did the DC test, everything checks out within 10%.
AC sidechain tests gave me these results:
AC level on TP3:
- Ratio 2 : 0.65 VAC Vs. 0.79
- Ratio 4 : 1.3 VAC Vs. 1.56
- Ratio 8 : 2.1 VAC Vs. 14.47
- Ratio 12 : 3.4 VAC Vs. 4.11
- Ratio 20 : 5.9 VAC Vs. 7.06
- Ratio SLAM : 6.6 VAC Vs. 7.06
Help! [/list]
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Yes, the setup steps 7 and 8 are necessary in all cases.
Also, does the compressor need to be engaged at this step?
Yes it does.
With it on, the highest reading I’ve been able to get is 1.550VAC.
You need to check if the issue is in the DOA or in the side chain.
Check you get no DC volts at the output of the DOA on L1 top pin. Any DC above a few millivolts here shows that there is an issue with your DOA.
If you can check the DOA in another device it is a good thing.
With the jumper JMP1 on 2-3, what is the DC voltage on TP6 (against 0V) at the 2 extreme settings of P6: should be between -4.5 and -1.2VDC
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Ok I’ll test the DOA and check back. Thanks
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I used another DOA from my EQ and that fixed the problem. Are there any specific things I should check on the SK25 or would ordering a new one be the way to go?
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I’m also getting D1-D4 LED’s constantly on with the second jumper in place and no changes when adjusting P7. Any ideas what this could be?
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Are there any specific things I should check on the SK25 or would ordering a new one be the way to go?
Check here: https://www.soundskulptor.com/forum/index.php?topic=9.msg9#msg9
I’m also getting D1-D4 LED’s constantly on with the second jumper in place and no changes when adjusting P7
Check the value and solder joints of P7, R54, R55, U1.
In normal use (single jumper on 1-2) is the meter behaving normally?
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As soon as I take the second jumper off, there’s no led response with or without the compressor engaged. Only those 4 LED’s light up when the second jumper is in place
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Check that you have not reversed one or more LED.
It can be checked by comparing the chape of the cathode with other LED's, by transparency.
You can also check with the DMM in diode mode, only red probe (+) on top and black probe on bottom can light up the diode.
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Thank you for your patience with this :)
I’ll do those checks but I may have found the issue: there was a 10K in place of a 120R resistor on the GR board. I’ll do those tests you mentioned as well as place the resistor in the proper spot.
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I soldered the proper resistor in place and the LED’s are lighting up properly. The module is up and running!
Again, thank you for your help and insight!
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Great news!
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Hey, I'm having the same problem. Only the first 4 green LEDs are on, adjusting P7 doesn't change anything. They behave well when compressing a signal in normal operational mode (1 jumper) , only it's just 4 of them... I've checked and tried all of the above, without succes yet. Is there anywhere else I could look?
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Check that you have not reversed one or more LED.
It can be checked by comparing the shape of the cathode with other LED's, by transparency.
You can also check with the DMM in diode mode, red probe (+) on top and black probe on bottom will light up the diode.
Check the resistors value and solder joints.
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Turns out resistors R5 and R20 were both dead.
Would those resistors perhaps be available from you? Or should I order them myself?
Thanks for the tips anyway :)
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Haha, never mind, I found out I switched those two around! Thought they were dead because I both measured them with the wrong scale on the multimeter. I guess you must get this a lot. It's all running swimmingly now, and it sounds great! Thanks again.
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Great!