Sound Skulptor forums
Build help and troubleshooting => LA502 Optical Compressor => Topic started by: JPK on January 04, 2021, 07:38:24 PM
-
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 on TP1. Any DC above a few millivolts here shows that there is an issue.
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. PEAK at 0.
Connect the voltmeter black probe to 0V and trace the signal on:
- R2 right pin: Should be at 0.7VACand follow the input voltage.
- REV1.3: R5 low pin should be at 0.5V when GAIN is on 100.
- REV1.4: R5 right pin should be at 0.5V.
- TP1: should go above 10V when GAIN is at 100.
Check the input transformer coils resistance
1 3 5
o . o . o
BOTTOM VIEW
o . . o o
10 7 6
1-5 ? 2 kohms
6-10 ? 2 kohms
Check the output transformer coils resistance
1 3 5 5 6 8
o . o o o o . o PRIMARY
BOTTOM VIEW
o o . o o . o o SECONDARY
16 15 13 12 10 9
1-3 ? 10 ohms (5 ohms if in circuit)
6-8 ? 10 ohms (5 ohms if in circuit)
9-12 ? 12 ohms
13-16 ? 12 ohms