Pioneer GM-X552

[mike49504]

I have this amp in for repair and its not producing rail voltage.

Theese are the voltages i have

FMG22s
1:8.79
2:8.30
3:8.79

FMG22r
1:8.79
2:1.54
3:8.79

Outputs
D2438
1:1.58
2:8.30
3:1.15

B1587
1:1.58
2:1.54
3:1.15

Where do i begin to check?? Any help would greatly be appericated

[Perry Babin]

Do you have a good square wave on the gates of the PS FETs?

[mike49504]

what would i set my scope to?? I dont see a square wave

[Perry Babin]

10uS and 5v/div.

Do you have a square wave on pins 9 and 10?

If not, post the DC voltage on the 494.

[mike49504]

I have nice square waves on pins 9 and 10 also have nice square waves on the gate legs of the fets

[Perry Babin]

With the scope set to 10v/div, do you have a square wave that swings ~2.5 divisions on the center leg of each of the power supply FETs.

[mike49504]

I checked it and bo it doesnt

[Perry Babin]

Do you have 12v there and 0v on the source leg?

Black probe on the amplifier's ground terminal.

[mike49504]

Leg1:5.54
leg2:13.90
leg3:8.74

[Perry Babin]

If this is on the power supply FETs, you have an open ground trace.