Same outputs shorting each time

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Hi, working on a Sound Stream PIC 1.1700D amp. Can someone shed some light on why a class D amp will short the same outputs each time? Gate resistors and Diodes check fine. Driver board checks fine. It shorts the same two outputs. One on the positive side and one on the negative. Thanks.
 
Here's the pics.
 

Attachments

  • 20160505_135152[1].jpg
    20160505_135152[1].jpg
    462.5 KB · Views: 151
  • 20160505_135208[1].jpg
    20160505_135208[1].jpg
    499.6 KB · Views: 152
The inductor looks like it may be shorted. If not, it soon will be (right arrow).

What's the light-colored spot indicated by the left arrow?

Have you desoldered the diodes that are in parallel with the gate resistors to confirm that they read similar forward voltage?
 

Attachments

  • inductor01.png
    inductor01.png
    447.7 KB · Views: 147
Last edited:
Yes I looked at that. They are not touching. I can shine a light between them. I'll insulate it anyway to make sure it doesn't short in the future.

The bright spot looked like white paint. Cleaned off easily with solvent and brush. No burned area around it. Doesn't appear to be rubbing away the insulation on the wire.

Checked the diodes out of the circuit. They read equally with all the other diodes.

Curious why the same two outputs short.
 
"Has the output filter capacitor failed shorted ?" No, output filter caps check fine.

I was trying to get an idea before rebuilding the power supply again. Decided to go ahead and put the power supply FETs in anyway. Now what I am getting is low voltage DC on the speaker positive and a loud high pitch squeal in the output. I haven't put the two shorted outputs back in yet.
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.