Alpine MRV-1000 repair

[Kei]

Got given it with one channel out with blown FETs and the chassis ground track which i have now replaced. I connected it up to my bench supply to see how it behaved with some power. Set the supply to limit the current and got as far a 4A 4.3V whilst checking voltages. Wasn't sure whether it was a good idea to push the current any higher as i'd rather not blow the FETs, though my bench supply can only go as far as 10A anyway. (wouldn't have expected the amp to require that much for quiescent) Even at this level the repaired side gets warm, whilst the working side remains cold.

Here are the measurements i got if they are of any use:

Repaired channel in red italic (No service manual, so I've numbered them 1 to 4, 1 being closest to the power terminals and 4 being up by the rectifying diodes)

FET 1
Gate - drain 0.01V
Gate - source -4.29V
Source - drain -4.30V

FET 1
Gate - drain 4.24V
Gate - source 0.00V
Source - drain -4.24V

Measuring with ground probe on power ground
FET1/2/3/4 (all measured the same)
Gate 4.30V
Drain 4.31V
Source 0.01V

FET1
Gate 4.24V
Drain 0.03V
Source 4.23V

FET2
Gate 2.20V
Drain 4.25V
Source 0.02V

FET3
Gate 0.02V
Drain 4.25V
Source 0.02V

FET4
Gate 0.02V
Drain 4.25V
Source 0.02V

Switch mode control IC 1 (closest to chassis, reckon this might be the repaired channel, but not certain)
1. 0.02V
2. 0.02V
3. 0.02V
4. 0.02V
5. 0.02V
6. 0.02V
7. 0.02V
8. 2.23V
9. 0.02V
10. 2.20V
11. 2.23V
12. 0.02V
13. 0.02V
14. 0.02V
15. 0.02V
16. 0.02V

Switch mode control IC 2 (further in)
1. 0.02V
2. 0.02V
3. 0.02V
4. 0.02V
5. 0.02V
6. 0.02V
7. 0.02V
8. 2.23V
9. 2.90V
10. 2.91V
11. 2.23V
12. 2.23V
13. 0.02V
14. 0.02V
15. 0.02V
16. 0.02V

[Perry Babin]

In the future, use the circuit board designations that are printed on the board (Q809, Q810...).

Confirm that R841-844 are within tolerance.

[Kei]

I would use the circuit designations if there were any. My unit has no labels printed on the PCB. If you've got the service manual, I can email you again.

Are these resistors the small (1/8W ?) from each FET as below?

[Perry Babin]

The circuit board designations may be on the bottom of the board.

[Kei]

I've had a look and only the IC's have designations on the underside along with R ch and L ch labels.

[Perry Babin]

The resistors that you need to check are the larger ones standing near the power supply FETs. They are 110 ohm resistors.

I'm assuming that you've confirmed that the gate resistors are within tolerance and that none of the FETs are shorted.

[Kei]

Not yet checked the gate resistors, assume they should be 100ohms. The FETs i put in tested good. (They were new) The old ones i removed (all 4) were shorted.