Receiver Yamaha RX-V577 DC PRT 000L protection problem - Page 1
Forum section: electronics / repair

author: briangg191
author_rank: Newbie
timestamp: August 20, 2017, 01:15:46 am
content: 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

author: denverpilot
author_rank: Regular Contributor
timestamp: August 20, 2017, 03:59:52 am
content: Just FYI... you'll need to put the image somewhere other than Photobucket for anyone to see it.

author: briangg191
author_rank: Newbie
timestamp: August 22, 2017, 02:59:33 am
content: Thanks for reply. I changed the image server.

author: mzacharias
author_rank: Frequent Contributor
timestamp: August 23, 2017, 10:48:44 am
content: 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.

author: briangg191
author_rank: Newbie
timestamp: August 24, 2017, 12:03:08 am
content: 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.

author: WaveyDipole
author_rank: Frequent Contributor
timestamp: August 24, 2017, 02:43:53 pm
content: 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?

author: mzacharias
author_rank: Frequent Contributor
timestamp: August 25, 2017, 02:25:12 pm
content: 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 WK452300These are surface mount transistors.

author: briangg191
author_rank: Newbie
timestamp: September 12, 2017, 06:16:26 pm
content: 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.

author: briangg191
author_rank: Newbie
timestamp: September 12, 2017, 06:25:00 pm
content: mzacharias,I ordered the 2SC2713 transistor parts.Sorry for my delay answers.Thanks guys.

author: briangg191
author_rank: Newbie
timestamp: October 20, 2017, 01:00:56 am
content: Hey guys,So i replaced the fourteen 2SC2713 transistors, but the the problem to be continued. Any more suggestions?

author: xavier60
author_rank: Super Contributor
timestamp: October 20, 2017, 01:38:29 am
content: 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.

author: mzacharias
author_rank: Frequent Contributor
timestamp: October 21, 2017, 01:30:07 pm
content: I see you have a service manual? Have you used the Protection Cancel Mode to facilitate troubleshooting?"If the protection function works and causes hindranceto troubleshooting, cancel the protection function bythe procedure below, and it will be possible to enter theselfdiagnostic function mode. (The protection functionsother than the excess current detect function will bedisabled.)While pressing the “TONE CONTROL” and “INFO” keys,press the (Power) key to turn on the power and keeppressing those 2 keys and (Power) key for 3 secondsor longer.The self-diagnostic function mode is activated with theprotection functions disabled.In this mode, the “SLEEP” segment of the FL displayflashes to indicate that the mode is self-diagnosticfunction 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.

author: Dmaumau
author_rank: Newbie
timestamp: March 07, 2019, 01:09:49 pm
content: 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 codesDSP MARGIN&DC PRT 0000LI´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

author: Dmaumau
author_rank: Newbie
timestamp: March 10, 2019, 12:30:45 am
content: All channels are outputing around -10VDC

author: mzacharias
author_rank: Frequent Contributor
timestamp: March 10, 2019, 08:27:40 pm
content: 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.