Sound Skulptor forums
Build help and troubleshooting => CP5176 FET compressor => Topic started by: JPK on December 17, 2020, 11:33:04 AM
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1. Check the usual suspects:
- Forgotten solder joint,
- Bad solder joint (reflow suspicious joints),
- Reversed components (electrolytics, diodes, transistors, IC's). In case of IC's, probably destroyed, better replace,
- Flipped IC's or transistors,
- Trim all the component leads and test pins as short as possible. Nothing must touch the chassis plate.
2. Check the DC voltages:
First check the supply voltages as described in the setup guide.
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.
Next, without any input signal, connect the voltmeter black probe to the 0V pin and note the DC voltages you get at the points shown on the attached picture. Compare with the expected results (more or less 10%).
3. Try to follow the signal
Send a good constant sine signal on input, like 1VAC measured between pins 2&3 of the input XLR.
Connect the voltmeter black probe to 0V and trace the signal on:
TP1, TP2, L1 top pin.
The reading should follow the input signal level.
The place where the signal drops will give you hints on where to look for.
4. Check the side chain
Input on 10
Out on 10
Attack on 0
Release on 10
Input signal sine 100Hz, 100mVAC
Jumper JMP1 on 2-3 [o o-o o o]
AC level on TP3:
- Ratio 2 : 0.65 VAC
- Ratio 4 : 1.3 VAC
- Ratio 8 : 2.1 VAC
- Ratio 12 : 3.4 VAC
- Ratio 20 : 5.9 VAC
- Ratio SLAM : 6.6 VAC
DC level on TP4:
- Ratio 2 : 0 VDC
- Ratio 4 : -0.5 VDC
- Ratio 8 : -1.3 VDC
- Ratio 12 : -2.5 VDC
- Ratio 20 : -5.5 VDC
- Ratio SLAM : -0.6 VDC
DC level on JMP1 pin 1:
- Ratio 2 : 0.6 VDC
- Ratio 4 : 0.9 VDC
- Ratio 8 : 1.2 VDC
- Ratio 12 : 1.9 VDC
- Ratio 20 : 2.3 VDC
- Ratio SLAM : 7.9 VDC
DC level on TP6:
-4.5 to -1.2 VDC depending on P6
DC level on TP5 with jumpers JMP1 on 2-3 and 4-5 [o o-o o-o]:
0.32 VDC