Yamaha RX-V467 power problem

[zoldi211]

Hi, I need Your help with Yamaha RX-V467. This receiver don´t turn on, voltage on the power switch (SW472) is 0V, PSW_DET pin of IC20 (CPU) is 0V too. Every VCC pin of the CPU have 3,3V. I replaced capacitors on Video (2) and Video (3) board: C3701, C3717, C3802, C3803. Transformer is ok. Here are the measured voltages:

+3,3M 3,3V
ACPWR_DET 2,54V (CB382)
ACPWR_DET 2,54V (CB381)
RESET 3,3V
PRY 0V
DEST 0,02V

Thanks.

Service manual:
https://elektrotanya.com/yamaha_rx-v.../download.html

[R_J]

Re: Yamaha RX-V467 power problem

You can try a manual /reset by momentarily shorting Q3803 (page 111) with power on. See if that makes a difference.

[zoldi211]

Re: Yamaha RX-V467 power problem

After shorting Q3803 I get 3,29V on power switch, but the receiver still don´t turn on. The relay don´t click.

+3,3M 3,3V
ACPWR_DET 2,54V
RESET 0V
PRY 0,13V
DEST 2,6V

[R_J]

Re: Yamaha RX-V467 power problem

It looks like you might have a problem in the reset circuit, I see you replaced the caps in that circuit already, were they bad? what was the reason to replace them? and did you use the same values and not go larger.
I your reset pin was 0 volts. Do not leave q3803 shorted, only do a quick short after you apply power to simulate the reset pulse. this pin should return to 3.3 volts.

[zoldi211]

Re: Yamaha RX-V467 power problem

One of this caps are bad, since previously the value of the ACPWR_DET was lower (1,2V).
By the way, what is the function of reset circuit?

[R_J]

Re: Yamaha RX-V467 power problem

The reset circuit tells the microprosessor to start running the program from its start point. without the reset the micro might start to run the program at any point in the program and not work properly or not at all.
the reset happens a split second AFTER power is applied, you need a dual trace scope to see it.

[zoldi211]

Re: Yamaha RX-V467 power problem

Wow ... Thank you

What should I try next?

I have measured all resistors, but all are OK.

[R_J]

Re: Yamaha RX-V467 power problem

In post #1 you have these values :
ACPWR_DET 2,54V (CB382)
ACPWR_DET 2,54V (CB381)
I assume you ment, 2.54v on AC_PWR (CB381)
That should be .5 volts, so check R3702 & R3703, then check the optocoupler, if you can.

another thing to try is to short AC_PWR to DGND on CB381 This should give you 3.3v on ACPWR_DET on CB382
It could be that the micro is missing this signal and thinks it is not pluged in.

[zoldi211]

Re: Yamaha RX-V467 power problem

Sorry, the correct value on CB381 is 0,2V (not 2,54V)...

The R3702 and R3703 resistors are OK. The problem may be in the IC375 ???

After shorting AC-PWR to DGND on CB381, nothing changed - ACPWR-DET still 2,54V and PWSW - 0V.

[R_J]

Re: Yamaha RX-V467 power problem

Check the voltages on the Video(3) board, Q3801 should be 3.3 on collector, if its low that might be causing ACPWR_DET to be low, it should be 3.4 volts
The line goes straight to the micro so it should be 3.4 volts, 2.54 might just be too low for the micro's logic

[zoldi211]

Re: Yamaha RX-V467 power problem

The measured voltages are filled to the attached pdf file, on page 111.

[R_J]

Re: Yamaha RX-V467 power problem

I don't know how you are getting 4.7 volts on Q3801 collector, but I would change D3803, or swap it with one of the other ones to see if it changes the voltage on D3803 anode. Check that R3804 100Ω is ok.
I don't know if ACPWR_DET is the problem, but that voltage should be 3.3 not 2.5

[zoldi211]

Re: Yamaha RX-V467 power problem

Problem is solved. Faulty CPU on Digital PCB. After replacing Digital PCB, receiver working even today without any problems. Thanks for help.

[goodpsusearch]

Re: Yamaha RX-V467 power problem

put a heatsink on it to prevent it from failing again