Audiopipe AP1500D issue

[Basshead1989]

Perry when I scope the output for the low side if I put the probe ground to the source leg the amp goes in protect as soon as I touch the ground to the source leg.

That's why the low side was grounded the amps Ground Terminal that's the only way I could read the low-side waveforms.

I'll get back to you with the answers for the other questions ASAP

 

[Basshead1989]

All waveforms are taking in .5v 5us.
Pics below.

 

[Perry Babin]

What's the resistance from the B+ terminal to the positive and negative speaker terminals (disconnect B+ to measure)?

 

[Basshead1989]

From B+ to speaker + it started at 5.98 megaohms and just kept climbing ever so slowly.

From B+ to speaker - it started at 7.05 megaohms and just kept climbing ever so slowly as well.

 

[Perry Babin]

I'd like to determine why you have DC on the low-side drive.

Are all of the rail caps completely discharged?

 

[Basshead1989]

The rail caps are not on the amp.

if I put the rail caps, output fets or rectifiers in the amp. The amp goes in protect so they are all out of circuit.

 

[Perry Babin]

What's the DC Voltage (black probe on the main ground) on the low-side source leg of the outputs.

 

[Basshead1989]

Okay black probe on Main ground Red probe on the low side Source pads I get a measurement of 10v then it drops to 9.79v then back to 10v.

It repeats that bouncing voltage.

 

[Perry Babin]

Black probe, same place, what is the DC voltage on the secondary center-tap?

Solder a rail cap on the negative rail (connection can be made with small jumper wires), what pin of the 494 is driving the amp into protect?

 

[Basshead1989]

Okay black Probe on Main ground Red probe on center tap I get. 0.001

On the tl494 it looks like pin 16 is causing protect it's reads. 12.11

 

[Perry Babin]

Lift Q87.

Does it still go into protect?

 

[Basshead1989]

Should I put q21 back in before I lift q87?

 

[Perry Babin]

No.

 

[Basshead1989]

Hey perry we're is q87 I can't find it on the board or SLA1500 schematic?

 

[Perry Babin]

Lift Q50 and 23. Does that allow the PS to power up?

 

[Basshead1989]

Yes it does

 

[Perry Babin]

Back to checking waveforms. You may now be able to ground your scope to the low-side source.

 

[Basshead1989]

Ok both waveforms are in .5v 5us probe x10 pics below.

Ground reference source pad for high and low side.

 

[Perry Babin]

Install all of the outputs and check those again.

 

[Basshead1989]

All outputs fets are installed scope set at .5v 5us probe x10 ground reference source pads of high and low side.

Pics below