Skar

[Hexhclass]

When amplifier powers on I get +11v on the RCA shield which after about a second goes to -12v.I replace both op-amp because one had DC on most pins but no charge.

Any suggestions?

 

[Perry Babin]

Black probe on primary ground, what is the DCV on the secondary ground/center-tap (no RCAs plugged in)?

 

[Hexhclass]

-11.86v

 

[Perry Babin]

With nothing connected to the amplifier, what's the resistance between the primary and secondary grounds?

 

[Hexhclass]

While doing this test I found a burn resistor connected between the main ground and center tap. Can that be the problem?

 

[Perry Babin]

That was what I was looking for. They commonly burn when a speaker wire shorts to ground.

 

[Hexhclass]

What value should I put in there?

 

[Perry Babin]

In the only class D skar I've seen, it was a 0 ohm jumper (R99). I used a 1 ohm resistor since I didn't have an SMD jumper and didn't want to jump it with wire.

Whatever you use, confirm that the resistance from the RCA input shields is not directly connected to the secondary center-tap. If it is, use a 1k resistor there.

 

[Hexhclass]

I install a 0 ohm and all seem to be ok now.

thanks.

 

[Perry Babin]

Push/pull/twist the transformer(s) to see if there could be an intermittent short.