Yamaha RX-V571 No Power, no screen

[bermo96]

Hi,
I have a Yamaha RX-V571 but unfortunately it doesn't work anymore. The screen isn't powering on and I can't hear the relays when I press the power button.

Here some voltages :

+3.3M (3.3v)
ACPWR_DET (3.3v)
MCPU_N_RST (3.3v)
PRY (0v) should be 3.3v according to the datasheet
DEST (2.7v)

When I do a reset ( info, tone, power ), I hear the relays clicking but nothing else.

Can someone help me troubleshoot this amp ?

[madan1]

Re: Yamaha RX-V571 No Power, no screen

Start with changing the 22pf/400V capacitor on the power board.

[bermo96]

Re: Yamaha RX-V571 No Power, no screen

I'm sorry but I don't have 22pf/400v on the power board.


Here is the link to the service manual (p.104 ) :

[madan1]

Re: Yamaha RX-V571 No Power, no screen

Hmm let me check the SM... meanwhile, can you post some pics of the power supply board ( the one with the relay for the primary side of the transformer )?

Alright, I guess this yama uses different board.. anyway, do you have the 5.5V standby rail?

[bermo96]

Re: Yamaha RX-V571 No Power, no screen

Yes I do have the 5.5v, I guess the fault may be in the regulators on the amplifier board but I don't know how to test it because it doesn't turn on.

Here is some photos of the power board.

[bermo96]

Re: Yamaha RX-V571 No Power, no screen

Update : I just checked the voltage and I have 12v and -12v on the regulators.

[madan1]

Re: Yamaha RX-V571 No Power, no screen

which rails are those +/-12?
On the power board I see only 5v standby... if you are reading somewhere 12v, this means that the cpu is actually activating RY371...

[bermo96]

Re: Yamaha RX-V571 No Power, no screen

There are the rails on the main board, for the amplifiers ic. That is weird because I have good voltages but there is an other protection that keeps it from powering up normally.

[bermo96]

Re: Yamaha RX-V571 No Power, no screen

Up ?

[R_J]

Re: Yamaha RX-V571 No Power, no screen

If you have the ± 12 volts on (page 100 of manual) you should also have the B+ and B- supplies. You need to check the voltage on the two plugs, CB100 & CB101, these pins should all be near zero volts, you may need to monitor a pin then turn the amp on to read the voltage as the protection will cut in. I suspect one of the amp outputs is bad causing the protection.

[bermo96]

Re: Yamaha RX-V571 No Power, no screen

Yes you're right, all the pins from CB100 and CB101 are showing really short voltage bursts , from 3.8 V to 12 V. Are you saying that the two amp ( IC100 & IC101 ) are blown ?

[R_J]

Re: Yamaha RX-V571 No Power, no screen

It could be any one of the thre output ic's causing the shutdown. IC100, IC101 & IC102. If one ic is bad it can effect the B+ or B- voltage on the other ic's so there output can also be effected.
Download the datasheet, then check the resistance between the output transistor pins. for example STK433-330, check the resistance between pins 3 and 18, 3 and 4, 3 and 6. although not exact it might show an internal transistor short. Do this for each output ic. if that does'nt show the bad ic then I would unsolder all the pins on IC100 and remove it, then see if the amp powers up.

[bermo96]

Re: Yamaha RX-V571 No Power, no screen

The resistance is between 25k and 35k ( still rising ) for all output, so I'm assuming this is not bad. I'll try to desolder IC100.

[R_J]

Re: Yamaha RX-V571 No Power, no screen

The are complex ic's so it may not be a reliable test, I picked ic100 because it drives the FL and FR speakers

It may not be an output related problem. Usually if the outputs have an issue you will still get a display with the error code.
You should be seeing the screen, so maybe something else is causing the amp to shut down that is associated with the no display.
Make sure you have display voltage, (page 103), check across F1 and F2 for 5.8vac, then check if you have the -FP voltage, check if you have -FP -38vdc. I see there is a line that goes to PS2_PRT
Also check that you have +5VA and -5VA

[bermo96]

Re: Yamaha RX-V571 No Power, no screen

I've taken out IC100 and no display, I'll desolder the other one the see if it does show up.

[R_J]

Re: Yamaha RX-V571 No Power, no screen

I've taken out IC100 and no display, I'll desolder the other one the see if it does show up.

I would check that you have the voltages on page 103, -VP, +5VA and -5VA, There is a protect line that checks those voltages and that might be triggering the shutdown.
Check the voltage on PS2_PRT and PS1_PRT

[bermo96]

Re: Yamaha RX-V571 No Power, no screen

I've checked -VP (5v ), +5VA ( 5v ), -5VA ( -5v ), and PS2 and PS1 are showing really fast 5v. I'm lost...

[R_J]

Re: Yamaha RX-V571 No Power, no screen

Ok, so +5VA and -5VA are ok, -VP is needed for the display, You will need to check Q3402 collector to see if it has -48 volts, if not check for an open R3401 (2.2Ω). R3401 will have about 40 volts AC on both sides, this feeds diode D3401, You should have about -48 volts across C3401
I think you are getting close to the problem.

[bermo96]

Re: Yamaha RX-V571 No Power, no screen

I have -37v on -VP... I think last time my oscillo was set to trigger at 5v. I was hoping that -VP was bad, but it's my fault. I don't know if this will help, but the output relays are constantly turning on and off.

[R_J]

Re: Yamaha RX-V571 No Power, no screen

You also said PS2 and PS1 were changing, was that checking with a meter? or scope? I would check the voltage with a meter. If those protect lines are changing, that would trigger a shutdown.
Looks like the voltages on PS2 and PS1 should be 1.1 volts

You might want to check the reset circuit on page 104, Check that Q3703 collector is 3.3 volts and not changing.