Yamaha RX-V583 DC Protection

[pbarker73]

Hi Folks

Long term lurker, first post.

I've got a Yamaha Rx-V583 which goes into protection mode when turned on. Bypassing protection the error is DC PRT: 000. Page 37 of the attached service manual suggests this is an abnormal DC output at the speaker terminal. Following advice from other threads here I've measured the voltage at the emitter resistors. All the channels measure 0V except SBL which measures 0.17V, so I'm guessing that this is the culprit. My question is, is it likely to be the output transistors - is it worth pulling the main board and removing them to check them? If not what would be a good next step?

Edit - can't attach the service manual it's too big. https://drive.google.com/file/d/1r3LtY7z8kruw282SWtCtpTQzt4xsjmVl/view?usp=sharing.

Thanks

[Swake]

Might be, or another one, or even a passive component. Start with checking all the Q's and D's in in that area. Page 130 Zone 4-5 / C-D-E
And also Q2005 on page 132.


DC PRT: 000 -> the '000' part indicates that the voltage was 0 Volt. That is somewhat strange. You could also have an issue with the power supply of that SBL amplifier.

[pbarker73]

Thanks Swake. Sorry it's taken me a while to get back to this. It's proving to be somewhat elusive!

I've checked all the Qs and Ds in the circuit and all appear to be reading good.

Guess I need to start looking at the passives.

[Swake]

Can you measure the power supplies?

If these read ok, do you have a scope to check the ripple on them?

[pbarker73]

I've measured the supplies leaving the power board (operation 4 on page 98). They all seem to be present and correct. I have a scope, but I'm definitely still learning and haven't tried to measure ripple before.