I have a CT Sounds 2000.1 class 4 clone. I Need some help with the mute circuit. This one is staying high on Pin 3 of the driver board.
I have working driverboard I swapped in with the same results.
Driverboard has a njm4560, lm219, and mmhc74m which all have been replaced.
Inductor has been replaced. Original was cooked.
Power section and audio section had failed in this originally.
Drivers and mosfets replaced in both sections.
Optocouplers were replaced.
all 3 of the 5v regulators are within tolerance.
driving an 80hz square to the driveboard i can see on pin 1.
I was able to verify the drive in the output section before I put the rectifiers in.
Driverboard voltages:
1. -.848v
2. .07v
3. 10.22v
4. -11.40v
5. 11.40v
6. .154v
7. .154v
8. .06v
9. 5.04
10. .300v
11. .300v
I have working driverboard I swapped in with the same results.
Driverboard has a njm4560, lm219, and mmhc74m which all have been replaced.
Inductor has been replaced. Original was cooked.
Power section and audio section had failed in this originally.
Drivers and mosfets replaced in both sections.
Optocouplers were replaced.
all 3 of the 5v regulators are within tolerance.
driving an 80hz square to the driveboard i can see on pin 1.
I was able to verify the drive in the output section before I put the rectifiers in.
Driverboard voltages:
1. -.848v
2. .07v
3. 10.22v
4. -11.40v
5. 11.40v
6. .154v
7. .154v
8. .06v
9. 5.04
10. .300v
11. .300v
Attachments
I don't know if the designations match but you should check Q21 and 22. Q21 should switch off and allow the mute voltage to drop to 0v. These are shown in the SLA1500 diagram.
Thanks Perry. Does anyone have a photo of this specific amp, the area around q63 also around the tl494? It looks like it was worked on before and I'm not so sure if I'm missing a zenner diode at zd2. There's a spot for it but it wasn't populated near the tl494.