PANASONIC SC-UA7 no 40V

[matszal]

Hi Everyone,

I am trying to fix a speaker for a friend. I have some knowledge but not enough to fully diagnose the potential issue with it . I only get around 320V on C1224, no 40V.
Tried to diagnose it as best as I could and there's no power on IC1201, positive gate voltage is needed to turn on the FET. VCC on pin 7 is missing and I don't follow schematic on how this is generated.
Any ideas please.

Full service manual can be downloaded from link below:
https://elektrotanya.com/panasonic_s.../download.html

Thank you!

[CapLeaker]

Your PFC isn't working cuz you only got 320V. I am just looking at this quickly. Figure out why the PFC isn't working. Is it because the PFC is bad or is it because it doesn't get turned on.

[matszal]

No voltage on PFC chip at pin 7. No short between pin 7 and pin 2. Not sure how to verify the chip.

[CapLeaker]

Not sure what that brown goo on that PSU is… maybe nicotine? Wash it off. I think I see bad solder joints too. Look up the next page from your pic #2. Check things out on the top part of the schematic page 66. There is a fuse, ic1402, etc.
for the PFC to work something needs STBY power first which is on all the time.

[R_J]

For the pfc ic to work (and IC1501) it needs vcc which is supplied by D1405 and switched by Q1402, Q1402 is turned on by Q1405 optocoupler. the optocoupler is controlled by QR1601 from the PCONT1 line on CN1851
As mentioned above, check F1401 fuse, if it is bad IC1402 is likely bad, if the fuse is good, check if you have any standby voltage on CN1851 pin9 or across C1601

[matszal]

Thanks R_J and CapLeaker, I am going to test it today and yes, that dirt is a nicotine and the smell is brutal. I will try one more time and if no joy I am going to trash it.

[matszal]

For the pfc ic to work (and IC1501) it needs vcc which is supplied by D1405 and switched by Q1402, Q1402 is turned on by Q1405 optocoupler. the optocoupler is controlled by QR1601 from the PCONT1 line on CN1851
As mentioned above, check F1401 fuse, if it is bad IC1402 is likely bad, if the fuse is good, check if you have any standby voltage on CN1851 pin9 or across C1601

Fuse is good and 5V standby is present. On Q1402 I have 25V on Emitter and Base and Collector is 0V

IC1402 voltages:
1. 5.9V
2. 1.05V
3. 2.36V
4. 11.1V
5. 317V

[matszal]

Another update: (I was unable to edit previous post)
No PCONT1 signal as I have power supply on my bench connected to mains and there's nothing else. Should I feed some voltage to QR1601 base?

Guys, I am a total noob. I need to connect all the PCBs together in order to make all the tests valid.

[R_J]

I would just short QR1601 Emitter to Collector, that should turn on the optocoupler and Q1402 to supply vcc to the rest of the circuit. I suspect the power supply is ok and there is a fault with the audio output circuit, if the processor senses a fault, it likely will not turn on the 35v for protection

[matszal]

Thank you very much for your help, patience and advice. I spotted a bulged capacitors C2147 and C2148 on DAMP circuit. After replacing both the unit is working again.