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Yamaha receiver.

Discussion in 'Electronic Repair' started by Dani, Sep 20, 2006.

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  1. Dani

    Dani Guest

    RX-V975A no display, relay clicks, & shuts down. Very hard unit to work
    on. You have to
    scrap these units, just to solder a few bad connections. Can't find
    anything online.
    Anyone work on one of these? Thanks, Dani.
     
  2. Arfa Daily

    Arfa Daily Guest

    Are you talking about the standby relay ? Unit looks like it's going to come
    on ok, then just drops back to standby ? I have had a similar problem to
    this on several Yammies, and it has proved to be bad contacts on the standby
    relay. Relay closes. Bad contacts arc and spit. Rails don't come up as the
    uP expects, so it shuts it back down. Worth a try before getting all
    technical with it.

    Arfa
     
  3. Doesn't look like a valid model number. Could it be

    RX-V795?

    Those of us who have had the (mis)fortune of having to work on surround
    receivers these past few years have mostly learned to work around the
    obstacles.

    You can rig a double-ended AC cord (use ONLY polarized ends, and make sure
    they match end-to-end).

    Plug the receiver's own AC cord into one of it's switched outlets.
    Plug your double-ended cord into the other switched outlet. This will bypass
    the relay. If everything pretty much works normally, the relay problem is
    confirmed.

    Remember: The AC cord polarity must match or there will be MAJOR sparks,
    since the AC line would be shorted if they were reversed. For this reason,
    only an experienced tech really should attempt this.


    Mark Z.
     
  4. Cliff Top

    Cliff Top Guest

    There are 2 protection circuits,

    1 shuts down instanly upon turn on if there's a major problem like a
    faulty/blown amp channel- to stop other damage occuring.

    The second trips at about 5 seconds, indicating a less serious problem like
    a low voltage rail missing....ie 5v regulator gone.

    Does it trip instantly.... or after 5 secs... I suspect from the fact the
    display isn't coming on, its instant.

    If so check for a +/- 50 volts appearing on any of the big (white?)
    resistors just in front of the big transistors on the heat sink- at the
    instant of turn on....you only get 1/2 sec to see. Normally you won't get
    any voltage.
    If a channels gone... it needs specialist fixing.

    Cliff
     
  5. P.S.

    This method can also be used to check DC offsets and all internal power
    supply voltages, regardless of protection status.
    For this reason, it is important to make sure you don't have a blown channel
    or some other high current draw before going too far with this method. A
    variac is most useful in this regard.

    Mark Z.
     
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