Rockford Fosgate BD1000

[seankane]

Hello I have a bd1000 I am repairing. The power supply was completely fried. I replaced all the IRF3205 fets and all their gates. The amp powers up fine and does not draw excess current but has no output. When the speakers are hooked up it is just silent with no noise or static. Any ideas??

 

[seankane]

Just to eliminate any other questions I replaced all the output transistors ( IRF 3415 and IRF 6215 ) and still no output. ??????

 

[Perry Babin]

What's the DC voltage on the pins of U21?


Pin 1:
Pin 2:
Pin 3:
Pin 4:
Pin 5:
Pin 6:
Pin 7:
Pin 8:

 

[seankane]

Pin1: -8.25v
Pin2: 0v
Pin3: -8.75v
Pin4: -9.60v
Pin5: 4.98v
Pin6: 8.27v
Pin7: -8.32v
Pin8: 9.77v

These are from U21 TL072C

 

[seankane]

These were obtained by holding the ground from my meter to the amps ground and testing the pins with the positive probe.

 

[Perry Babin]

That appears to be OK.

What's the resistance from the 3rd leg of Q101 to the positive speaker terminal (no power applied to the amp)?

 

[seankane]

Looking down on Q101 last leg to the right resistance between that and the positive terminal no power applied what so ever is .1 ohm

 

[seankane]

If I hold the leads on for a little while it starts at .5 ohms then bleeds down to .1 ohms and eventually 0 ohms. Dont know if this matters???

 

[Perry Babin]

Check it again but this time, move the output filter inductor. Does it change significantly?

What's the DC voltage measured directly across the black and red twisted wired?

 

[seankane]

Output filter inductor? As in the crossover adjustment knob? The voltage from the power supply side to the the output side measure across??

 

[seankane]

The voltage across the twisted wires started at 105v and bled down to 94.5v and stayed. Moving the crossover knob while testing the rsistance between leg 3 and + terminal made no change.

 

[Perry Babin]

The output filter inductor is the coil near the speaker terminals.

 

[seankane]

I put my leads on leg 3 q101 and positive speaker terminal and pushed on the filter inductor in different places moving it and pushing on it and no change still reads 0.1 ohms.

 

[seankane]

Tried it again and no change still 0.1 to 0.0 ohms. No matter how hard i push or wiggle.

 

[Perry Babin]

You'll need your scope for the next tests.

Set the timebase to 10us. Set the vertical amp to 5v/div. Do you see a triangle waveform on pin 7 of U11?

 

[seankane]

No it is not a triangle its like a small wavy line.

 

[seankane]

Looks like a continuous S across the screen.

 

[Perry Babin]

What's is the DC voltage on all of the pins of that IC?


Pin 1:
Pin 2:
Pin 3:
Pin 4:
Pin 5:
Pin 6:
Pin 7:
Pin 8:

 

[seankane]

Pin 1: -.003v
Pin 2: .001v
Pin 3: -.104v
Pin 4: -9.60v
Pin 5: .001v
Pin 6: .001v
Pin 7: -.220v
Pin 8: 9.77v

 

[Perry Babin]

Do you have a square wave that deflects approximately 1.5 divisions above and below the reference line on pin 1?