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Old 01-23-2022, 01:26 AM   #1
matticas
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Question Yamaha Amp - strange power issue

Hi all;

I found this forum from this thread; https://www.badcaps.net/forum/showth...&highlight=PRY

And I have a unique issue that I hope some experts on here might know about - but with similar 'design' to the thread above.

My Yamaha RX-V861 will not turn on "once it's flat" (I think a cap discharge?). But if I manually power up the relay on the power PCB, the entire amp comes alive and works perfectly. From there, I can turn it off and on again as much as I like, providing I turn it on within about 3-4 seconds of turning it off. Past this time, it's "flat" and I need to manually trigger that relay.

Research and poking with a multi has found the PRY signal works fine when the amp "isn't flat", but the PDET signal is the one going flat per say. While it's running normally, turning it on/off that signal changes from 0V to 5.1V no issues, but if I leave it "go flat" that PDET signal drops to ~2-3V and fluctuates a lot, and the amp never comes back on.

Does anyone know where these PDET and PRY signals come from? (the microprocessor or something else). I have the service manual / circuit diagrams, but I can't work out it's design and behavior off paper.

Lastly the Config menu I can access, change menus and sub menus, but I can't actually select / change anything? I've pushed every button, nothing actually changes.

I've downloaded the service manual and it mentions nothing about "selecting" a menu item, just initial access and navigation.

Thanks, hope to hear from anyone what maybe still familiar with these older amps...
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Old 01-23-2022, 12:00 PM   #2
R_J
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Default Re: Yamaha Amp - strange power issue

You likely have bad capacitors in the power supply, like C2535 (2.2/50); C2534 (2.2/50) and C2538 (1/50)
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Old 01-23-2022, 02:42 PM   #3
matticas
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Default Re: Yamaha Amp - strange power issue

Quote:
Originally Posted by R_J View Post
You likely have bad capacitors in the power supply, like C2535 (2.2/50); C2534 (2.2/50) and C2538 (1/50)
Hi RJ;

To test them, do I need to remove them from the PCB and use (my mate's) LCR meter?

Thanks
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Old 01-23-2022, 07:02 PM   #4
R_J
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Default Re: Yamaha Amp - strange power issue

Quote:
Originally Posted by matticas View Post
Hi RJ;

To test them, do I need to remove them from the PCB and use (my mate's) LCR meter?

Thanks
I guess you could, I would just replace them.
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Old 02-10-2022, 03:34 PM   #5
matticas
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Default Re: Yamaha Amp - strange power issue

Hi all;

I finally brought some replacement caps, and the first one I targeted was the 22nF/630V greencap on the power supply board.

Yep, worked first try zero issues. Old dead Cap was measured to be 5nF once I took it out.

Thanks all for the input. Still got me fd how that cap was messing with the 5V signals to/from that power board to the Video board, but hey, half of me is happy my amp is working (painful few weeks with TV speakers), other half of me was looking forward to a new amp....
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