Yamaha rx-v3900 - Page 1
Forum section: electronics / repair

author: pwkwong
author_rank: Newbie
timestamp: August 22, 2015, 10:04:48 am
content: Hi All,The receiver is shutting down on abnormal voltage protection, with the message "PS1 PRT 84 H" (norm 43-66). When I tested the outputs that the protection monitors, I get the following values Q20 (5.0): (4.94 measured), Q21 (12.3): (11.70 measured), Q22: (-12.1): (-11.83 measured), IC16 (-11.8 ): (-11.74 measured) and IC 15 (12.0): (11.96 measured).It seems that the outputs on Q21 and Q22 is a bit low, but I am not sure what the tolerance is. Is it likely that the transistors are faulty? Is there other areas that I should look at?Regards

author: singapol
author_rank: Frequent Contributor
timestamp: August 22, 2015, 04:13:42 pm
content: Please provide a link to the schematic you are refering to...we are not psychics.The voltages you measured seem within tolerance. Until we look at the schematic...

author: pwkwong
author_rank: Newbie
timestamp: August 23, 2015, 03:28:25 am
content: Thanks for the reply. I have attached the schematic and block diagrams for the outputs. Would C69 & C70 affect the output the transistors? I also measured the output of D20 and they were 20.7 and -20.9 and seems to be ok as well.

author: singapol
author_rank: Frequent Contributor
timestamp: August 23, 2015, 05:48:06 am
content: Quote from: pwkwong on August 23, 2015, 03:28:25 amThank you very much for your cooperation.Now I apologise if I'm unable to continue to helpas my internet connection is about to end.That said I think others will help as the schematics are available for anyone interested to see.The first place to look is the block diagram as it gives an overall organisation of the AV amp system.Refering to your 1st. post the error message is " PS1 PRT 84H"( norm 43 - 66).I don't know what it means unless I have the service manual at hand which I don't.But you zoomed in to Q20 which is in "Power3 or PS3" ( My interpretation).Which your measurements indicate all is normal as in schematic.BTW it supplies power to DSP pcb.Anyway still theblock diagram is where the clues are.Looking at block diagram of PS1( power supply1) it supply 3 signal inputs to main processor namely:Look at input arrow to main processor IC402.Also the output signals.DEST-???PDET - Power detect/RSET - Reset?I traced these 3 signals to "Power4" in 1st.schematic( schm.pdf). It's an auxilary transformer that supplies startup power and power to relay "RLY1"where it goes to S10 on connector W1 to PCB-FUNCTION(1).DEST,PDET and /RES are also there.I think the problem is likely to be here.Since this is power supply. I would check and measure voltages:1. Q6 power fet.2. optoisolators IC1,IC2 and associated circuit.3. Relay RLY1 and Q24. IC3 TC4013 logic ( but not likely).5. Check voltages at W! connecor.Troubleshooting should be systemstic,Power4 supplies signals that main processor will detect first before continuing with other functions/processes.All the best.Edit: Just realised that "Power4" is not indicated at the block diagram of S1 which I think is an oversight so newbies might have a hard time if they don't trace the 3 signals that S1 inputs to main processor.

author: mzacharias
author_rank: Frequent Contributor
timestamp: August 25, 2015, 03:46:00 pm
content: PS1 monitors +/- B1, B2, +/-12V, +/-RY, +5D2, +5I, +3.3HD. This from page 74 of service manual.I'm betting on a bad -12V regulator IC.

author: pwkwong
author_rank: Newbie
timestamp: August 26, 2015, 03:04:11 am
content: Thanks for the reply. -12V is generated from Q22 (-12.1) and I measured -11.83 and -RY (-11.8 ) is from IC16 and -11.74 is measured. So it seems that Q22 is bad, or could there be something in the circuit that is pulling the voltage down? Is there are a way to check the ICs or just replaced and recheck voltages?

author: mzacharias
author_rank: Frequent Contributor
timestamp: August 26, 2015, 05:11:00 pm
content: The voltages don't seem so far off. If you continue to hold down the buttons for several seconds at power up it will go into protection cancel mode, one of the front panel indicators will flash (don't remember which) and you can take voltage readings at your leisure. If all the power supply voltages are good, there could possibly be a bad summing resistor. Pretty rare, but I have seen it.

author: pwkwong
author_rank: Newbie
timestamp: August 29, 2015, 06:22:45 am
content: Just an update, I got into the diagnostic mode and measure all the voltages that PS1 monitors:+12(12.3): 11.84V-12(-12.1): -11.72V+5D2 (5.0): 5.07V+RY(12.0): 12.1V-RY(-11.8 ): -11.74V+5I(5.5V): 5.66VApart from +12 & -12 are a little bit low, it seems to be within spec. It appears that the voltages are monitored via a voltage summation circuit through the resistors you mentioned. I also measured the ps1 voltage and it was 1.69V, which matches the PS1 84 value that the display is providing. The other monitoring voltages are OK (PS2) and (PS3). I notice PS1 also monitors the AC voltages for the regulators and B1 supplies, but I assumed they should be ok.Look like the next step is to remove the board and measure the summing resistors, as the resistors are SMDs on the bottom side of the board. So do I need to desolder the resistors or can they be measured in circuit?

author: mzacharias
author_rank: Frequent Contributor
timestamp: September 03, 2015, 12:02:16 pm
content: There is another possibility. It may be possible to use an external power supply and a resistor to force the DC PRT line up or down as required to keep the DC value in range. If the receiver still shuts down - it could be a bad gate (input) on the microprocessor. Once again - rare, but I have seen it happen (on other models that is - I work on lots of receivers.)

author: pwkwong
author_rank: Newbie
timestamp: September 05, 2015, 05:37:22 am
content: Thanks for the reply. I managed to removed the board and measured the summing resistors. The results are:-12: R81 (47k), approx 14k measured+12: R80 (47k), approx 14k measured+5D2: R79 (22k), approx 10k measuredRY+: R46 (47k), approx 13k measuredRY-: R47 (47k), approx 24k measuredAC1: R44 (120k), approx 13kAC2: R45 (120k), approx 13kThere is no resistor on the +5I rail as it is connected to a transistor (Q44) which looks like it will pull the PRV voltage down if there is an issue with the output.I am not sure what to make of the results as it does not match the values. However, I suspect it is because the resistors are in circuit and other components are affect the resistance readings. Still I would expect that R80 would match R81 and R46 with R47 as they are connected to the +&- 12 voltage rails?mzacharias, do you think R47 is bad or is there another reason for the higher resistance measured? A higher resistance on R47 compared to R46 would cause the PRV voltage to increase.

author: jitter
author_rank: Frequent Contributor
timestamp: September 05, 2015, 07:35:51 am
content: When I looked at this thread, there was something very familiar about it. Looking at the schematics, it became even more familiar!Dave took on the repair of a different Yamaha receiver that didn't want to power up and was led in circles until some people pointed out a common fault: C405 (in that one, it's C4 in this one).Here's that vid:EEVblog #379.It seems that this receiver has the same circuit, so my tip before you continue: take out C4 and measure to see if it still is within spec.

author: pwkwong
author_rank: Newbie
timestamp: September 05, 2015, 09:55:43 am
content: Hi jitter, thanks for the reply. It seems that the symptoms are a bit different. I can get it to switch on and access the diagnostic mode, but the protection circuitry is shutting it down if I don't bypass it. I can also access the noise generation function in the diagnostic mode and test all the amp channels.

author: jitter
author_rank: Frequent Contributor
timestamp: September 05, 2015, 10:48:16 am
content: Please don't make assumptions, test C4 anyway to be sure. Highish ripple may lead to different symptons yet have the same cause, it is a different model, after all.If it turns out fine, then hey, no harm done. But you will(or at least) if you find, after spending a lot more time, that it was the cause all along... Just a friendly tip from someone who learnt that the hard way...

author: mzacharias
author_rank: Frequent Contributor
timestamp: September 05, 2015, 09:20:39 pm
content: The capacitor in Dave's dumpster dive was a completely different issue and does not relate in any way to this person's problem.(authorized yamaha servicer for 18 years.)Quote from: jitter on September 05, 2015, 10:48:16 am

author: pwkwong
author_rank: Newbie
timestamp: September 13, 2015, 10:16:41 am
content: Hi, Just an update. As my old soldering iron wasn't hot enough to for lead free solder, and as I am still waiting for my hot air gun to be delivered, I end up soldering a normal metal film resistor (47k) in parallel with R47. As R47 is a SMD, I end up soldering onto a couple of jumpers on top of the board, which wasn't pretty.Anyway, I reinstalled the board and the switched the AVR on........ and it stay on! I measured the voltages again and it was the same, except for the PRV voltage which is now 1.07 volts so is in the normal range. So it seems that the summing resistor had gone high. I ran the amp for an hour on radio and it seems to be ok. I guess to be sure I should remove R47 and measure the resistance.Thanks mzacharias for the pointer to the summing resistors, you definitely know your stuff. How come you don't put any more videos on youtube?

author: redboy130578
author_rank: Newbie
timestamp: November 14, 2017, 05:02:42 am
content: Hello everyone .. I have a rx-v3900 receiver with similar symptoms. it turns off when I increase the volume. pwkwong was your problem solved with this method that mentions mzacharias?Do you think that could be the solution to my problem?help me please.

author: mzacharias
author_rank: Frequent Contributor
timestamp: November 15, 2017, 01:48:34 pm
content: Quote from: redboy130578 on November 14, 2017, 05:02:42 amThis more often points to problems with speakers or speaker wires, or simply playing too loud.

author: redboy130578
author_rank: Newbie
timestamp: December 07, 2017, 04:02:46 am
content: Quote from: mzacharias on November 15, 2017, 01:48:34 pmHello mzacharias, thanks for answeringthe speakers are fine. I assure you because I use them with another similar amplifier.but the RX-V3900 turns off when the volume increases (25%) even without speakers.when entering the diagnostic it shows the code: "I (SP) PRT Y"in fact the service manual says:Cause: The line between speaker terminals is shorted. Supplementary information: As the excess current is detected after operation of the speaker relay, the shorted speaker terminal and the connected speaker can be identified.check all audio channels and they have soundthe test was done with the volume below 25% power.I also found a hdmi port is damagedthe contacts(pin) are touchingcrushedIt could be the cause of the problemCould it be some short channel or component like transistor or damaged resistance?what opinion can you give meHow could I check moreThank you

author: mzacharias
author_rank: Frequent Contributor
timestamp: December 07, 2017, 06:01:35 pm
content: This particular model Yamaha is much more difficult to troubleshoot. I've fixed a couple but...Anyway, I hope you have a 'scope to look at the output of each channel output to look for distortion, premature clipping, etc as volume is increased.Do measure the resistance of each speaker connector from positive to negative while the unit is OFF. Rarely there is a shorted or leaky .01uF capacitor associated with a speaker output; they do fail occasionally.On page 153 of the service manual there is transistor Q321 which is the over-current trigger. Each amp channel has a transistor such as Q320 which would trigger it in the event of an over-current situation. In theory, one should be able to determine which channel is triggering the protect. A leaky sense transistor for example could cause this. A (way) out of spec emitter resistor could trigger it, since the voltage across it would rise quickly with increased volume.That's about all I got for the moment.

author: redboy130578
author_rank: Newbie
timestamp: December 17, 2017, 06:45:38 pm
content: Hello mzachariasI already measured the outputs of the speakers with the amplifier off as you suggestedand I found that only the left front channel marks a resistancethe channel measures from 005 to 002 ohms on the 2000 ohms scale of the multimeter (50 to 20 ohm on 200 ohms scale)the initial reading is from 005 to 002 from more to lesseven so the channel takes out sound but it is lower the volume than the others channels (it is remarkable)the other channels did not show resistanceDo you believe that this channel is the channel of the problem?Do you believe that the cause is the capacitor c377 shown in the service manual on page 153?I send you imagethanks for your help

author: mzacharias
author_rank: Frequent Contributor
timestamp: December 18, 2017, 06:31:04 pm
content: Yes, that's definitely wrong. I would check that cap immediately. There is also a resistor/capacitor combination across that channel. If that cap, C378 was bad, it would cause the same trouble.

author: redboy130578
author_rank: Newbie
timestamp: January 29, 2018, 06:41:22 pm
content: THANK YOU VERY MUCH mzachariasIS WORKING .

author: mzacharias
author_rank: Frequent Contributor
timestamp: January 30, 2018, 02:40:46 pm
content: Quote from: redboy130578 on January 29, 2018, 06:41:22 pmThanks for the update! Often we never hear the rest of the story.