Receiver Yamaha RX-V577 DC PRT 000L protection problem

[briangg191]

Hello,

I have a Yamaha RX-V577 receiver with protection mode activated. When i started self-diagnostic function, is show in your display DC PRT 000L. Based on the service manual, is a DC amplifier problem. So i checked the amplifier board and i found a -48.1 V in the collector transistor (Q2129), but the manual says it should have -1.033 V in the collector transistor. The attached image shows the transistor problem. I already did the replacement transistor 2sc2229 without success. Does anyone have any suggestion? Sorry my bad english.



The service manual can be downloaded by link:
https://www.4shared.com/office/Wd2r_eB-ei/service_manual_yamaha_rx-v477_.html

[denverpilot]

Just FYI... you'll need to put the image somewhere other than Photobucket for anyone to see it.

[briangg191]

Thanks for reply. I changed the image server.

[mzacharias]

What is the DC voltage at the EMITTERS of the output transistors? On the affected channel - or is there a DC problem on all channels?

This is critical information.

[briangg191]

Hello,

The problem is just at the center channel. I have the same DC voltage (-44.0V) at the emitters of the output transistors (Q2155, Q2154). But if i take off (Q2129) transistor, i have 0V DC voltage at the emitters of the output transistors.

[WaveyDipole]

What are your voltages like around Q2116 and Q2124? I am guessing that there may be a lack of bias current at Q2124 via Q2116. This would leave the collector at Q2129 floating close to the negative rail voltage as soon as it is turned on.

Perhaps resistor R2145 is o/c?

[mzacharias]

I'm suspecting the differential pair Q2102 and Q2109. Pretty common problem. Yamaha recommends replacing those transistors on all seven channels. Fourteen transistors in all.

Part number WK452300

These are surface mount transistors.

[briangg191]

WaveyDipole,

The voltages like arround Q2116 and Q2124 are -44.0 V DC. The same voltage at the Q2129 transistor collector. The R2145 resistor measures 100 ohms, that´s ok.

[briangg191]

mzacharias,

I ordered the 2SC2713 transistor parts.
Sorry for my delay answers.

Thanks guys.

[briangg191]

Hey guys,

So i replaced the fourteen 2SC2713 transistors, but the the problem to be continued. Any more suggestions?

[xavier60]

The differential pair's emitter current might be too low, check the 10K resistor and that it has the correct voltage across it.
The voltage across R2145 will indicate the Voltage Amplifier's operating current. About 5ma.

[mzacharias]

I see you have a service manual? Have you used the Protection Cancel Mode to facilitate troubleshooting?

"If the protection function works and causes hindrance
to troubleshooting, cancel the protection function by
the procedure below, and it will be possible to enter the
selfdiagnostic function mode. (The protection functions
other than the excess current detect function will be
disabled.)
While pressing the “TONE CONTROL” and “INFO” keys,
press the (Power) key to turn on the power and keep
pressing those 2 keys and (Power) key for 3 seconds
or longer.
The self-diagnostic function mode is activated with the
protection functions disabled.
In this mode, the “SLEEP” segment of the FL display
flashes to indicate that the mode is self-diagnostic
function mode with the protection functions disabled."


This will allow you to troubleshoot at your leisure without interference from the protection circuit. You can look at any of the protection triggers, and see what monitored voltages are wrong or missing.

[Dmaumau]

Helo guys.

The topic creator has moved on I imagine, but I am having the same problems with a Yamaha RX-A3040.

It started with a noise like a tv with no signal on the front channels and after a while progressed to all channels.

I still used it as a processor for a while, with an external amp, but the decided to run a firmware update to clean the software.

After that, it worked for a few seconds, turned off and now it only powers up with the protection bypass procedure.

It the shows these codes

DSP MARGIN
&
DC PRT 0000L

I´ll check tonite if there is really DC on the outputs, but reading the topic it seems that it might be a little bit difficult to debug than that, right ?

Until then, any educated guesses ?

Thank you very much for any and all help.

Mauricio

[Dmaumau]

All channels are outputing  around -10VDC

[mzacharias]

In the service manual there is a "Protection Cancel" mode that allows you to troubleshoot a problem such as this. Press and hold Tone/Balance and Info and continue to hold them down while pressing Main Zone (Power), and continue to hold them for 2-3 seconds.

The problem is likely some power supply voltage missing or wrong, or an amplifier offsetting bias voltage missing.

You seem to have the service manual; the procedure is described on page 30 of the PDF.

I tried to upload the manual to HiFi Engine but the upload "hung" at 99% twice in a row - don't know if it made it.

There's some latency there anyhow, could be a few days before it would show up.