Yamaha rx-v757 av reciever keeps turning off

[Sneaky1]

Hello everyone

So i've got this "old" av reciever that's keep turning off.
It has been sitting on my attic for about 3 years, since i got a newer model. And it worked perfectly when i put it there.

So far i've cleaned it for dust inside and checked for any loose wiring and everything looks fine.

I've also gotten the service manual. Found it here: https://www.manualslib.com/manual/1053815/Yamaha-Rx-V757.html
(Dont know if its okay i link it here?)

And when i start the reciever in diagnostics it says: ps prt 034K
It has also saved the error code: psprt 035

As far as i can tell it's a power supply protection code, but where to go next, i've got no idea.

 I got a background as car mechanic so i've got no issues using a multimeter or soldering.

Hope anyone can help.

[Rasz]

when is it turning off? when you want to play something?
supply protection will kick in if for example amp output mosfets are blown and shorted - you can check those by measuring in diode mode across legs (unit turned off), it can also trigger if power supply itself is wounded in some way - check voltages

Dave fixed similar unit by replacing small cap in the 5V power supply section



it seems to be a common fault mode on those units, here 757 with same problem

[Sneaky1]

It's turning off after 1 second on.

I've trying replacing the cap in the videos with this one: https://elektronik-lavpris.dk/p102769/mkp10n022k630-10-mkp-capacitor-22nf-630v-10-p10/

But it still turns off after 1 sec. :/

Dunno if the fault codes point in any direction?

[KevinA]

Page 16 of your service manual states that PSPRT (Power Supply Protection) voltage must lie between 36-49V; outside of these, the protection shuts down.

Your line is low at 34V

[Kerlin]

I have one of these same AV receivers that I got as faulty years ago and repaired it. Didn't need a circuit, used a repair technique know as Milking the front panel.
I am finding it a brilliant bit of gear certainly sounds better than most.
I almost blew it up once by connecting a bad load to it, but the protection worked well and kicked in then shut it down and prevented the smoke getting out.
For me its proved to be like only very few things,a real keeper, like my sports car.

My problem was with the stand by power supply and the symptoms were the same as yours, this is an example of how it could be many things.
Eliminate the guess work and allow for proper diagnosis instead of using it "might be this or that" by providing some measurements.]

Replacing components one at a time by using guess work is a technique I see used by many car mechanics who try to fault find electronics in cars they don't understand electronics. If you ever get the chance its great fun to listen to them talking to a customer after one of these repairs. Using this method they have often replaced half or more of the electronics, very expensive.

Measure before and after voltages. It will be easier to measure the start up before voltages if you lock an auto ranging multimeter onto the correct range as it can then provide measurements more quickly.

[mzacharias]

Page 16 of your service manual states that PSPRT (Power Supply Protection) voltage must lie between 36-49V; outside of these, the protection shuts down.

Your line is low at 34V

The values given do not represent the voltage directly. For some reason Yamaha does not report the voltage errors directly.

It goes something like this:

The sum at the output of a resistor summing network is normally approximately zero volts.

Take the source voltage, usually 5 volts on the older ones, divide by 255.

multiply the error code by this remaining decimal value to see the actual voltage the microprocessor is reporting.

5V/ 255 = .0196078431

.0196078431 x let's say 45 = .88V

So the sum of the resistor network is approximately .9 volts HIGH, suggesting a negative voltage source may be LOW.

[mbz]

The sum at the output of a resistor summing network is normally approximately zero volts.

OK, old thread, might be useful to others, working on a RX-V657/V757 with PS PRT 52

I disagree that the summed voltage is normally about 0Vdc, service manual shows for RS expected range is 36-49 so my 52 is just out of tolerance. The expected range is non zero as it needs to cater for different fault scenarios like +ve/-ve volt regulators failing open/shot.

This fault has been kicking my butt, looking at drift in summing resistors and slightly leaky caps and GND connectios.

[wasedadoc]

The sum at the output of a resistor summing network is normally approximately zero volts.

OK, old thread, might be useful to others, working on a RX-V657/V757 with PS PRT 52

I disagree that the summed voltage is normally about 0Vdc, service manual shows for RS expected range is 36-49 so my 52 is just out of tolerance. The expected range is non zero as it needs to cater for different fault scenarios like +ve/-ve volt regulators failing open/shot.

This fault has been kicking my butt, looking at drift in summing resistors and slightly leaky caps and GND connectios.

Back in 2016 I acquired a RX-V750 with similar shutdown problem.  I don't remember the PS PRT code.  Fault was failed 5 Volt regulator. (TO-220 package)

[mbz]

Thanks for chiming in, voltage regs and rail caps were the first thing checked, all regs outputting spec voltages. The clue is the small departure from spec 52 versus 49, a failed regulator would(?) cause a larger departure from spec, eg, 90. I need to work through the math to work out for different failure scenarios and PST diagnostic. Spent a fair bit of time troubleshooting, isolating boards/pulling out connectors etc...