Soundstream PCA2000D

[m4ick]

This is a clone amp.

I am so frustrated with this amp, self oscillating is a pain, I just wish I could see what the drivers are doing with no outputs installed.

I replaced both banks of outputs (31N20D) and Q124 and Q125 (MPSA42).

As soon as it tries to come out of protect it instantly shorts the low side outputs.

What else besides Q124 and Q125 would make this happen?

 

[Perry Babin]

You can test the drivers without the outputs in the amp. Check item #31 on the Generic Class D - Type 2 page.

 

[m4ick]

Mine only has 27 items.

 

[m4ick]

Do I tie the inductor input to negative speaker? That's how I've always seen it done to get the high side signal to appear.

 

[Perry Babin]

I don't think that was necessary for this amp. If you find it necessary, make a note of it here.

 

[m4ick]

My tutorial only has 27 items on that page. Do I have an older version of the tutorial?

 

[Perry Babin]

It appears so. I think that was added in mid 2011. Email me if you have any other questions regarding the tutorial.
babin_perry@yahoo.com

 

[m4ick]

With all the outputs removed I powered it up and R192 went up in flames. Replaced Q124 and 125 again along with R192 and R192 burns up again as soon as it is powered on. Any idea why?

 

[Perry Babin]

Short between solder pads for outputs or drivers?

Is the board leaking internally? Item #22.

 

[m4ick]

Found a solder bridge, I looked really hard at first but it was just a hairline.

Thanks.

 

[m4ick]

OK, I'm back to where I originally was. I have +-70V and +-15V. I do not have ANY drive signal to ANY outputs.

I confirmed that SW is being driven to ground.

I'm clueless at this point.

 

[Perry Babin]

Driving the audio signal into the amp with no outputs, do you have drive signal?

 

[m4ick]

No.

 

[Perry Babin]

What's the DC voltage across R175?

 

[m4ick]

5.08V

 

[Perry Babin]

That's OK.

Do you see the audio input signal on pin 1 of the driver board?

 

[m4ick]

No I do not.

That wouldn't cause the low side outputs to fry would it?

 

[Perry Babin]

No. Is that still a problem? I thought that you found a solder bridge causing that.

Is it still burning the resistor?

Do you have the master/slave switch set to master?

 

[m4ick]

Removing the shorted output caused the solder bridge that fried the resistor. Then I replaced q124 and 125 and the resistor. Now no drive signal.

It is set for master.

I assume I need to find out why there is no drive signal first then see what happens when I put the outputs back in.

 

[Perry Babin]

You must have signal on pin 1 before you will have drive signal (outputs out of the circuit). Determine why you have no signal on pin 1 (nearest the op-amp end) of the driver board. There is a generic schematic (just above section 15) to help you follow the signal.