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chipper 26th May 2012 01:58 AM

rockford fosgate punch 800a2 non working
Hello everyone! I got my self a nice project! A Rockford Fosgate punch 800a2 a amp I've dreamed of having of my own :D but it's not working.... When i apply power to B+ & GND just power no REM it puts my 10 amp power supply into protect so that indicates the power supply is shorted. I checked all 8 MTP75N05HD's and they measure a dead short on the sources. And on the sources i get a resistance of .715 on all 8 of the fets on the gates but the from drain to source they measure .000 and beeeeeeeep on my meter. I also checked the outputs IRF640s measure out fine in both channels and IRF9640s.

What could have cause the power supply to short?

Perry Babin 26th May 2012 05:31 AM

What is the resistance between legs 1 and 2 for all of the power supply FETs?

chipper 26th May 2012 06:27 AM

Actually it's something with the transformer there's a smd resistor near by some of the legs of transformer where if I touch it will arch or move it around arch. I believe that's made the fets seem as if they were shorted but the amp still powers on. I removed it from the heat sink and it powered right on! Put it back in the sink it still powers on but of I touch or move the transformer it arch. I'll get a picture of where it sparks at.

Is problem common on these amps?

chipper 27th May 2012 07:16 AM

2 Attachment(s)
There seems to be some arching under the transformer amp actually works fine both channels but when you pull, twist the transformer it makes like a small spark by two of the legs of the transformer near that smd resistor.
and the amp had a broken gain pot on i believe was the left channel when i tried adjust it it made the speaker act weird and almost blew my kenwood book shelf speaker and then a smd cap blew right by the speaker terminal. I thought i fried the amp by the smell of what burned but was a smd component that burned up. I replaced the gain pot now that channel plays good i can adjust it and everything but im wondering if that part is important or what? please get back to me as what i can do for the transformer thing.. Thanks

chipper 27th May 2012 07:19 AM

and i thought maybe something was so i reflowed some solder on the joints of the transformer where it made a spark but that still did nothing its somewhere on the windings.

chipper 27th May 2012 07:36 AM

1 Attachment(s)
see that resistor between the caps and transformer theres two of the legs of the transformer where it arches when you move it or twist it.

seankane 27th May 2012 08:18 PM

Maybe you should remove the transformer. Then unwind it a little and put some heat shrink or something around the problem area then rewind and install it.

Perry Babin 27th May 2012 08:33 PM

If it's arcing where the terminal windings meet the rest of the windings, coat a piece of cardboard with adhesive and wedge it between the windings. The cardboard will insulate it and the adhesive will keep it in place.

chipper 27th May 2012 09:13 PM

Would it be worth it to remove it and repair as necessary? I mean it doesn't look like a lot to remove but I'm just wondering that's pretty much it needs for it to be completely working.

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