Punch 45 PC-045C pre mosfet power supply help

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mikep28

Member
2015-02-20 5:28 am
I have a old punch 45 circa 1986-87. It has a power supply problem that I can't seem find the issue with. When I got the amplifier in it has one power supply transistor blown D44VH10 and a D40D8. I replaced both D44V and both D40D8. Also replaced both 4148 switching diodes. The thermal swith was also open. It was replaced. Now get ~14v at the D44's but amp does not show any rail voltage. I get nothing at anything on that side of the diagram. So therefore no LED. I Have another identical amp sitting side by side. All the a56 and a06 read the same. Any idea where to look.
 

mikep28

Member
2015-02-20 5:28 am
If I hold my Fluke 12 meter set to diode check. Black lead on chassis ground, and red lead on the base of either D0D4 (now A06) or Q5 (a06) it will cycle power on for a second or so, shut off and repeat about every 3 or 4 seconds.


Let me add to this : it does it also to the smalls leads on the left side of the transformer and other components in that area..
 
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