Got a PPI A204 amp (not the .2 version with ceramic boards) that is now going into protect and I am having trouble tracing back the circuits. At first the amps power supply wouldn't even come on, but found out C37 and C38 (input filter caps) had broken legs and was preventing a complete circuit for the input power to the amp. Installed a couple spares from a parts amp, now the power supply starts up, but the amp goes into protect. All PS fets and output fets check not shorted or open, and I get +13.94v and -14.29 for the op amps (via 2n6487 and 2n6490). Q46 appears to be sending too high of a voltage to pin 1 of the SG3525. A schematic would be sweet, but anything helps, thanks!
SG3525
1. 2.58v
2. 2.57v
3. .03v
4. .34v (cannot dial this in on scope)
5. 2.06v (nice saw tooth on scope)
6. 3.65v
7. 2.05v (nice saw tooth on scope)
8. 4.90v
9. 1.46v
10. 0.0v
11. 1.24v (tiny ugly pulse trying to start)
12. 0.0v
13. 11.84v
14. 1.18v (tiny ugly pulse trying to start)
15. 11.84v
16. 5.19v
SG3525
1. 2.58v
2. 2.57v
3. .03v
4. .34v (cannot dial this in on scope)
5. 2.06v (nice saw tooth on scope)
6. 3.65v
7. 2.05v (nice saw tooth on scope)
8. 4.90v
9. 1.46v
10. 0.0v
11. 1.24v (tiny ugly pulse trying to start)
12. 0.0v
13. 11.84v
14. 1.18v (tiny ugly pulse trying to start)
15. 11.84v
16. 5.19v
Attachments
Well I am a big old idiot! Had a bunch of personal stress in my life in the last two weeks and repairing amps is supposed to be my fun, but I may have been a bit distracted, or just an idiot. The problem was the broken off legs on the power supply caps, the amp was not going into protect after that, IT WAS POWERING ON. The red LED is power, not protect. Thanks Perry and jkrokenberger, sorry to have wasted your time. Deep breaths!
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