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Yamaha RX-V3900 Powers On then Off (Protect)

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    Yamaha RX-V3900 Powers On then Off (Protect)

    Hi All,

    The receiver is shutting down on abnormal voltage protection, with the message "PS3 PRT 181" (norm 114-180). I assume the issue points to the POWER (3) so I got into the diagnostic mode and measure some of the voltages at the points to the main transformer and these seems close to there values as found on the schematics

    CB15
    AC 9.9 (GY): Pin1 10.47V ac
    AC 9.9 (GY): Pin2
    AC 30 (WH): Pin5 15.76V ac
    AC 30 (RE): Pin6

    If I measure across Pin4&Pin6 I get the 30V ac. I suspect the schematics is wrong as I get +- 20V across the rectifier, hence the measurement point should've been across those pins not 5&6 but 4&6 to get 30V AC

    I also measure the voltages across POWER 1 connector to mains transformer and get

    CB11
    AC 6.8(YE): 6.53 V ac
    AC 15.8(PU): 16.37 V ac
    AC 9.1(OR): 9.64 V av
    AC 9.2(BL): 9.09 V ac

    I performed some other measurements and got close to the values as shown in the schematics however in most cases these voltage values would seems to be within tolerance, but have concerns due to the way this AMP performs its protection checks via a voltage summation circuit to monitored the voltages and triggers it to go into protection shut down

    Now I've I got into the diagnostic mode and also replaced the common fault: C405 (it's C4 in this one) just as a precaution.

    I've attached a few pages and full schematics found below

    RX-V3900

    I am hoping people can help me find the cause to fix this AMP
    Thanks

    PEACE
    Kosti
    Attached Files

    #2
    Re: Yamaha RX-V3900 Powers On then Off (Protect)

    PS3: Detects +5VA, -5VA, +9VA. Check those voltages to make sure they are ok

    Comment


      #3
      Re: Yamaha RX-V3900 Powers On then Off (Protect)

      You can see PS3 the MCU monitoring voltage divider at R75,R76,R77 for "PRVS". It adds the three rails together. The displayed number is raw 8-bit A/D count 0-255.

      Comment


        #4
        Re: Yamaha RX-V3900 Powers On then Off (Protect)

        Originally posted by R_J View Post
        PS3: Detects +5VA, -5VA, +9VA. Check those voltages to make sure they are ok
        OK great thank you, I will try and check this on this weekend, Its a big amp and I have to keep moving if off our dinner table to work on it

        Originally posted by redwire View Post
        You can see PS3 the MCU monitoring voltage divider at R75,R76,R77 for "PRVS". It adds the three rails together. The displayed number is raw 8-bit A/D count 0-255.
        Thank you,

        EDIT, makes sense now that I looked at the schematic
        R75 - 47K ,R76 - 27K ,R77 - 27K
        I will measure these when I get the opened up and report back.

        Just to add there will be some delay as I was measuring the caps on the PS1 around C4 area and found the 3300uf to be out so have ordered some of these to replace so hopefully they arrive next week

        PEACE
        Kosti
        Last edited by Kosti; 11-08-2019, 12:22 AM. Reason: updated details

        Comment


          #5
          Re: Yamaha RX-V3900 Powers On then Off (Protect)

          Hello All

          I've finally had a chance to get back to this today, so I have looked to confirm the voltages of these regulators based on what PS3: Detects +5VA, -5VA, +9VA at CB23.

          Checking those voltages reads +4.94VA -4.94VA & +8.99VA so they are ok right?

          So do I need to measure R75 - 47K ,R76 - 27K ,R77 - 27K values if the voltage readings are close to values? I will try and do this but given they are on the flip side of the board, its dismantling the whole amp which I wanted to avoid.

          FYI - I also replaced the 2 x 3300uf caps on PS1 as well since these were also out in value thinking the ripple may be contributing, but still no luck in keeping this to stay on.

          So if diagnose code shows PS3 PRT 181 and the voltages check out ok where would I start to zoom in on the issue if PS3 is reporting to be ok?

          Hoping for some further clues chaps, as always, thanks for the guidance

          PEACE
          Kosti

          Comment


            #6
            Re: Yamaha RX-V3900 Powers On then Off (Protect)

            Hi All

            Anyone have any further idea of why this amps shuts down? Basics checks seems to come up ok and the receiver is shutting down on abnormal voltage protection, with the message "PS3 PRT 181" (norm 114-180).

            I've checked the voltages of PS3: Detects +5VA, -5VA, +9VA. to make sure they are ok and they are measuring +4.94VA -4.94VA & +8.99VA.

            Really need some guidance chaps

            PEACE
            Kosti

            Comment


              #7
              Re: Yamaha RX-V3900 Powers On then Off (Protect)

              Try warming PS3 with an hair dryer so the PSU is warm, not hot so you can’t touch it anymore. Turn the amp on and see if the problem presists.

              Comment


                #8
                Re: Yamaha RX-V3900 Powers On then Off (Protect)

                Check the voltage on CB18 pin 3 (PRVS) [page 154 of manual] it should be 2.8~3.2v
                If you look at page 114, locate IC402, to the left is R4039, check the voltage on each side, it should have 1.1v on the test point.
                This is the line that is triggering the PS3 error, so maybe there is a poor connection somewhere between the power supply and the micro.
                Attached Files
                Last edited by R_J; 11-30-2019, 06:42 PM.

                Comment


                  #9
                  Re: Yamaha RX-V3900 Powers On then Off (Protect)

                  Originally posted by CapLeaker View Post
                  Try warming PS3 with an hair dryer so the PSU is warm, not hot so you can't touch it anymore. Turn the amp on and see if the problem presists.
                  OK will try this tonight

                  Originally posted by R_J View Post
                  Check the voltage on CB18 pin 3 (PRVS) [page 154 of manual] it should be 2.8~3.2v
                  If you look at page 114, locate IC402, to the left is R4039, check the voltage on each side, it should have 1.1v on the test point.
                  This is the line that is triggering the PS3 error, so maybe there is a poor connection somewhere between the power supply and the micro.
                  Thank you very much for the next tip, very much appreciate you taking the time to help out. I will get this checked today and report back

                  Thanks heaps!!!!

                  Comment

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