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Yamaha RX-V667 no signs of life

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    Yamaha RX-V667 no signs of life

    A few weeks ago my trusty Yamaha RX-V667, which I've had for 9yrs since new, stopped working without warning. We have all our HDMI sources connected to it, and these could no longer be accessed. The standby light has gone out and neither the remote or power button can start the receiver. When I press the power button I cannot hear any relays.

    Before this, the amp has never put a foot wrong and sound quality was perfect.

    I have downloaded the service manual from here:
    https://elektrotanya.com/yamaha_rx-v.../download.html

    I've scoured this forum and the internet for threads on dead Yamaha AV receivers, but have drawn a bit of a blank in finding a solution that works. Here is what I've tried so far:

    - The three button 'reset procedure' from the service manual.
    - Checked the main plug fuse and the internal fuse in the power supply. Both fine.
    - Checked continuity of the primary winding on the main transformer. Measured fine.
    - Visual check for 'toasted' components or bad caps. Nothing obvious.
    - Having read about 'C405' on Yamaha receivers (and watched the EEVblog video), I replaced the 22nf 600V capacitors C3701 and C3717 on the "Video(2)" board that seem to do a similar job in the standby circuit. There was no change, and the old capacitors tested fine on my multimeter.
    - Bridged the main relay in an attempt to get it to power up, but still nothing lit up.
    - Checked voltage across the main relay and it's basically zero regardless of the power button being pressed or not.
    - Removed the "Video(2)" standby power supply board and powered it up on the bench. All of the outputs at CB379 are as expected - I get 5.49V on the +5.5V power supply.

    Where it gets interesting is that when the receiver is fully assembled, I only measure about +0.2V on the +5.5V inputs to CB73 on the main 'Digital' board (with all the HDMI sockets). If I unplug the connector I measure +5.49V again. My meter is showing continuity between the +5.5V and DGND inputs at CB73. This makes me think that something on that board is shorted somewhere, which is a shame as it looks like the hardest board to repair!

    Have also tried to get a reading on a +3.3V line and that was at close to 0V also.

    I'm fairly sure it's an issue with the parts of the amp connected to standby power at this stage. According to the block diagram on pg83 of the manual, the +5.5V feeds a bunch of regulators on the main 'Digital' board. At this point I'm stuck with how to proceed.

    In terms of equipment and experience, I have a decent temperature controlled iron and a multimeter. I don't own a scope or any other test/repair equipment. I've completed successful repairs in the past e.g. re-capping a motherboard, repaired traces and battery damage in old computers, rebuilt a valve amp with new components, but am not experienced in fault finding and have never attempted any surface mount soldering. I can read a circuit diagram but most of the time don't understand how the circuit actually works. I'm basically a novice, but not a "n00b".

    It seems a shame to throw the receiver out if there could be a simple fix. I don't have a 4K TV yet, and don't plan on upgrading from 5.1 to Atmos any time soon. I also don't have a tonne of time to spend on this as I've got a 9 month old in the house. Am therefore looking to see if anyone has any suggestions of simple things I can try or has resolved a similar issue before. Any advice gratefully received.

    #2
    Re: Yamaha RX-V667 no signs of life

    You could have a problem with the standby power supply, If you want to bench test just the power supply you will need to provide a load on the +5 volts to test it properly. If you can get at the board in the unit, check the voltage across C3708 (it should be 18 volts) I would just replace C3707, C3708, C3710 & C3711
    Your standby supply is likely working but can't produce any current so it shuts down.
    Last edited by R_J; 03-15-2020, 10:18 AM.

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      #3
      Re: Yamaha RX-V667 no signs of life

      Originally posted by R_J View Post
      You could have a problem with the standby power supply, If you want to bench test just the power supply you will need to provide a load on the +5 volts to test it properly. If you can get at the board in the unit, check the voltage across C3708 (it should be 18 volts) I would just replace C3707, C3708, C3710 & C3711
      Your standby supply is likely working but can't produce any current so it shuts down.
      Thanks for the quick reply. Hadn't thought of that. Think I should have spares of those values of capacitor in my toolbox so will have a go next weekend.

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        #4
        Re: Yamaha RX-V667 no signs of life

        You should at least try and load the +5v for a half amp, so a 10Ω 5 watt resistor would work. With no current draw the smps will likely show it is working, but when loaded it shuts down.
        And those small value caps tend to dry out overtime, and will look ok and might even check ok, but will not work properly. The standby circuit is ON 24/7/365
        Last edited by R_J; 03-15-2020, 12:17 PM.

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          #5
          Re: Yamaha RX-V667 no signs of life

          I've now replaced C3707, C3708, C3710 and C3711. Unfortunately there is no change, receiver is still totally unresponsive.

          I read 21V across C3708.

          I measure 5.5V across a 10ohm resistor briefly attached to the standby supply (had to use a lower wattage resistor and the supply happily cooked it), so I think the standby supply is OK.

          Again, with everything connected I get basically 0V across the 5.5V supply on the Digital board (with an occasional spike of up to 1V), with the 5.5V and Ground inputs at CB73 seemingly being shorted.

          I tried disconnecting all the other cables from the Digital board apart from power and still can't get a 5.5V reading when it's connected to the standby supply.

          Therefore think that there has to be a problem on the main digital board, but have no idea where to start, unless there's a common fault with Yamaha's of this era?

          Pg110 of the service manual shows where the +5.5V line goes next. Maybe C790 would be a good place to start? All the other components are tiny and probably beyond my abilities to replace.
          Last edited by Andy1979; 03-29-2020, 09:40 AM.

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            #6
            Re: Yamaha RX-V667 no signs of life

            If the standby supply cooked the load resistor, it should be supplying enough current, so when it is connected to the plug CB73, I would expect something connected to the +5.5v would also be getting hot (or warm) I doubt C790 is shorted, I would suspect a regulator or a mlcc cap (like C782 etc.) Are you able to remove any of the coils like L719 or are they smd type? Check around with your finger looking for a warm regulator ic or mlcc cap next to it.

            Have you checked the resistance of the +5v line to ground? what is the reading?
            Last edited by R_J; 03-29-2020, 11:37 AM.

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              #7
              Re: Yamaha RX-V667 no signs of life

              Thanks again for quick reply. All coils are tiny SMD type.

              I've checked whole board, in particular around the 12 ICs that feed off the +5.5V line, and nothing is getting hot. Perhaps that's because I'm reading such a low voltage across the +5.5V inputs when everything is connected? Maybe the standby PSU can't start up?

              Resistance of +5.5V input on the Digital board to Ground is around 0.7ohms with the power off. With the power on it fluctuates, mostly between 5 and 35 ohms.

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                #8
                Re: Yamaha RX-V667 no signs of life

                Just to close this out, I was unable to trace the exact fault so decided to buy a new receiver (Marantz NR1609). Enjoyed trying though and feel that I took it as far as I could.

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                  #9
                  Re: Yamaha RX-V667 no signs of life

                  Originally posted by Andy1979 View Post
                  Thanks again for quick reply. All coils are tiny SMD type.

                  I've checked whole board, in particular around the 12 ICs that feed off the +5.5V line, and nothing is getting hot. Perhaps that's because I'm reading such a low voltage across the +5.5V inputs when everything is connected? Maybe the standby PSU can't start up?

                  Resistance of +5.5V input on the Digital board to Ground is around 0.7ohms with the power off. With the power on it fluctuates, mostly between 5 and 35 ohms.
                  0.7Ω is way too low, something must be shorted, You CAN NOT check resistance with power applied. It does'nt work that way. The meter supplies a small voltage to calculate the resistance, with voltage applied that 5~35Ω reading means nothing.

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