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Question about Yamaha rx-v457 power board

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    #21
    Re: Question about Yamaha rx-v457 power board

    All the rails are up, the MCU should be running. It is either dead or it has decided it is unsafe to power up the main relay.

    The signal /PSW (power switch) should be at 5V and drop to 0V when you press the power switch. I would check /PSW at CB456, it then goes to the MCU.

    Q452 is a digital transistor (built-in base resistors) and needs at least 3V to turn on, but it's probably OK as PDET can also turn on the (Q451) +5S. Looks OK.

    Can you measure the voltages on CB452 and CB453, to see if a signal is coming in that would make the MCU refuse to turn on power.

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      #22
      Re: Question about Yamaha rx-v457 power board

      /PSW at CB456(pin 7) gives nothing even when power on button is pressed.

      CB452 -
      pins:
      1 - 5V
      3 - 1V
      4-10V
      5-5V

      Other pins had no volts or up to 0,20V.

      cb453 - pin 5 has highest 0,25V. Other pins have about no volts(read about 0,01...0.15)V

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        #23
        Re: Question about Yamaha rx-v457 power board

        CB456 /PSW (on/off pushbutton switch) is a problem.

        Looking at OPERATION board, /PSW has a pullup resistor to +5M, it should be at 5V only unless button SW861 pressed or stuck, which takes /PSW low to 0V. This is at CB801 pg.85, which then goes to CB456 pin 15; pg. 90 and then directly to IC451 MCU pin 74.

        Is there 5V power to OPERATION board?
        You could also try the remote control on/off.

        CB452,453 is from the power amp, good- all are nothing because main relay is off.
        Attached Files

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          #24
          Re: Question about Yamaha rx-v457 power board

          I tested it again. There is no /psw 5v at operations board. On operations board CB801 pin 7 is 0,074V and when on button is pressed it drops to 0.

          Same situation is with CB456 pin 15.

          IC451 pin 74 has 0,026V and when button is pressed it drops to 0,05

          So I guess the problem is that voltage from Operations board is too low?

          Unfortunately I do not have the remote for this unit so I can not try powering it on from there.
          Last edited by rauno45; 12-12-2017, 11:48 AM.

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            #25
            Re: Question about Yamaha rx-v457 power board

            There seems to be no +5M power going to the OPERATION board, for the on/off pushbutton.

            +5M is made by IC452 on 457SUBTR board. You said it measures 5V OK, but somehow not making it through ribbon cable from CB456 to CB801. I would look for broken wires or connector pins, trace it back with ohmmeter and see where the open-circuit is.

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              #26
              Re: Question about Yamaha rx-v457 power board

              I traced pin 15 of CB456 back to IC451 pin 74 /psw. It was missing.

              I can not find IC452 right now. I suspect that it might be on the other side of the board where IC451 is situated, however taking it apart seems to be quite a hassle because this board is simuntaneously connected to 6 other circuit boards physically somehow. Isnt there an easyer way to test this?

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                #27
                Re: Question about Yamaha rx-v457 power board

                The service manual is confusing because it covers six models: RX-V557/HTR-5850/DSP-AX557/RX-V457/HTR-5840/DSP-AX457

                When you press and hold the power button, CB456 pin 15 /PSW should go from 5V->0V.
                CB456 pin 18 should always have +5M present.

                The signals go all over the place.

                From the power board, +10V standby "S10" comes to MAIN(2) on CB121, then leaves on CB122. pg.86. The same "hop" happens for +5M.

                CB122 ribbon goes from 19pin to 17 pin, then to SUBTR board CB452 pg.90; You might have the cable backwards?

                CB452 S10 goes to IC452 voltage regulator, then output +5M goes back out CB456, to OPERATION board CB801 pin 4 (then to pushbutton). Also +5M goes back out to power board on CB401.

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                  #28
                  Re: Question about Yamaha rx-v457 power board

                  Greetings.I am looking for some help on repairing,leader transistor checker LTC-906.It,s not working,the bad light stay on when power on.MY email.sheenhig@hotmail.com.urgent

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                    #29
                    Re: Question about Yamaha rx-v457 power board

                    CB456 pin 15 does not have 5V as described before.
                    CB456 pin 18 has about 5 v present
                    The ribbon cable going from CB122 to CB452 on my model has 17 pins on all sides. As far as I can see it was connected correctly.
                    CB452 has S10 and 5m. 5m is on pin 1 and s10 is on pin 4.
                    yes cb452 pin 4 10v goes to ic452. I found it now. It is present on the middle pin(10v). There also is +5,558v output preset. From there it does not reach CB456.
                    I have done some tracing and found the following:
                    Output +5M is gotten from D452. +5,5v is in the input and +5v is in the output.
                    After that it goes back to CB452 pin 1 and CB456 pin 18(not 15). On pin 18 5V is preset.

                    Am I missing something here or are we looking at the wrong diagrams? There definetly seems to be something wrong here.

                    I also checked all the ribbons and they were the right side facing the metal contacts. I also double checked the model number and it indeed is rx-v 457 natural sound av receiver.
                    Last edited by rauno45; 12-22-2017, 12:56 PM.

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                      #30
                      Re: Question about Yamaha rx-v457 power board

                      I think we got the same schematics, I might have mixed up a pin number.
                      +5M output goes to two places - CB452 and CB456.

                      You have +5M power at CB456 pin 18, but not getting to CB122, so that's a problem.
                      With power off, use ohmmeter to trace down the open circuit. The ribbon connector might have a bent pin.
                      Or some problem with on/off pushbutton, and the two boards there.

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                        #31
                        Re: Question about Yamaha rx-v457 power board

                        I checked the ribbon cable. The pins are not bent(they look brand new as well as the sockets. Also the pins are facing the metal pins in the socket) and when measured the +5m line reaches the test point on the board that CB122 is on(behind the socket on the board).

                        However troublesome is that according to the schematic there should also be:
                        pin 4 at CB452 PRY = 10v preset
                        pin 11 at cb452 PRY = 0v preset
                        pin 14 at CB452=10V - not preset
                        pin 17 at CB452=5v - not preset.

                        So I guess there is some problem with the pushbutton? How can I test all that circuitry?

                        Also cant I just jump PRY at CB452 pin 4 to pin 11 to see what happens? Because PRY test point near CB122 also seems dead.

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                          #32
                          Re: Question about Yamaha rx-v457 power board

                          You have to follow the /PSW signal.

                          /PSW should be high at +5M (due to R847 OPERATION(1) board) and go low 0V when power button pressed.
                          The power button has a separate PCB: OPERATION(2) so also check at CB803<->CB861.

                          Check for 5V toggling at the power button, and go back until you reach CB456.


                          If you disconnect and force PRY to 5V through resistor, the amplifier will power up- but the MCU is still sleeping. So still dead.

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                            #33
                            Re: Question about Yamaha rx-v457 power board

                            I checked the operations board and here is what I found out: CB456 pin 18 goes to operations 1 U801. it has 3 pins. Middle should be ground and the pin on the other side does not have any voltage on it. It goes back out to CB801 and from there CB452, but with no voltage.

                            CB803 to CB861 is fine. Only problem I could see is that the pins going to the switch on cb861 - F1 and F2 were shorted no matter what. I could not measure +5V toggle form operations2 board anywhere. The pin on operations board named SYSPSW had 0,something volts on it. It goes back to CB801 and from there to CB452. Could I try jumping 5V to syspsw rail?
                            Last edited by rauno45; 01-15-2018, 02:11 PM.

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                              #34
                              Re: Question about Yamaha rx-v457 power board

                              OK, I most likely found the culprict. The problem is that psw from power button is missing. It goes to CB456 pin 15, which does not have anything. Also the MCU pin 74 does not have anything. However +5m reaches the MCU board from the main power supply board. I will try to jump that signal from +5M input to MCU board and jump it to syspsw at operations board trough CB456. That way MCU also should get power.

                              With that workaround I should get 5v and dropping of it to the correct place.

                              Comment


                                #35
                                Re: Question about Yamaha rx-v457 power board

                                Hello guys,
                                I have a Yamaha RX-V459 and i don't have power.
                                I entry in self diagnostic and i have the error protection DC PRT 023H.
                                Where is the error, what should I measure?
                                Thank you in advance.

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