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Yamaha RX-V795 Error PS PRT

Discussion in 'Power Electronics' started by Druvey, Nov 6, 2019.

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  1. Druvey


    Nov 6, 2019
    I have the mentioned amp. Pulled it out of storage to use and it comes on the the PS PRT :14% error for 1/2 second then turns off. I’ve read the other posts on here about this. I will be changing all the caps on the power board but wanted to ask a question re voltages measured. I have the service manual and it states the voltages but what I get is much higher. Please see photo. Are the voltages in red a minimum or what should be seen?

    Attached Files:

  2. Harald Kapp

    Harald Kapp Moderator Moderator

    Nov 17, 2011
    Welcome to EP.
    No these are not minimum values but expected values (give or take a few %).

    14.5 V instead of 12.6 V is a tad too high but should be acceptable (15 %, this may well be due to an equivalent overvoltage on the mains input plus tolerances.
    19.5 V instead of 8.8 V indicates a failure of the voltage regulator. Do not operate the unit under these conditions as the overvoltaeg may damage components.
    Disconnect connector CB821 (left side).
    1. Check Jumper J821. It should be open. If it is closed, open it and measure again the output voltage. If the voltage now is 9.8 V you should be set.
    2. If not then check the voltage across D823 (9.3 V) . If this voltage reads o.k., then go on to the next step. If this voltage is not o.k. (>> 10 V), replace the diode (note: simply re-soldering the pins may suffice). Measure again.
    3. Measure the voltage at the base of Q822. Is it close to 9.3 V, then replace Q822. If not check the connection between D823 and Q822.

    Let's see where this leads.
  3. Druvey


    Nov 6, 2019
    Thanks for the input. I’ll try the suggestions this weekend. Will update when I have anything further.

    Last edited by a moderator: Nov 6, 2019
  4. Druvey


    Nov 6, 2019
    I have just realised the service manual I was working from was for the 795a model, not 795. I Have emailed Yamaha to try to get correct service manual to check if the voltages are the same.
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