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Venerable Amana RR-10 Microwave

Discussion in 'Electronic Repair' started by Larry B, Nov 4, 2004.

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  1. Larry B

    Larry B Guest

    We love our RR-10 and are the original owners (since 1979). Chromed out
    with stainless interior and digital touchpad. I do have a service manual but
    it does not go into detail on the digital module. The digital module in this
    particular model was made by Essex.

    Last weekend, someone used it (not personally witnessed) and the digital
    module (Touchmatic II) went dead. I don't know what mortal code they entered
    on the touchpad but it is truly dead. I have a rusty old RR-10 in the garage
    for parts. So, I replaced the tube thermal cutout switch (which was open)
    and the digital module. The rusty digital module works great but has a poor
    Wife Acceptance Factor. Unfortunately, the original module is still dead. As
    a further clue, when the the connector plug for the module is plugged in,
    the buzzer should chirp. The original doesn't even chirp.

    I took it apart and found a cap that had caused the underside of the PC
    board to turn color so I replaced it. I also cleaned to the contacts on an
    unenclosed relay, too. Still dead. Since a new digital module is $170 I was
    hoping to get some hints as to what would be the most likely part(s) at
    fault. Since whatever happened took out the thermal cutout sw, I thought
    there may be some kind of deductive logic that could be applied here.

    Thanks for any and all insights,

    Lar
     
  2. First, check to see if there is a rectifier diode shorted which may have
    caused the capacitor to burst. Next if the capacitor caused the board to
    change color then you have electrolyte all over the PC board causing
    current leakage. Try cleaning with strong alcohol, dry it and then check
    for corroded solder connections. If it still won't work, its likely
    trashed.

    --
    Joe Leikhim K4SAT
    "The RFI-EMI-GUY"

    The Lost Deep Thoughts By: Jack Handey
    Before a mad scientist goes mad, there's probably a time
    when he's only partially mad. And this is the time when he's
    going to throw his best parties.
     
  3. Larry B

    Larry B Guest

    There appear to be 3 identical bridge rectifiers on this board. Two are
    side by side and the 3rd is off doing its own thing. One of the pair is
    directly connected to the cap in question. Should I replace just the one or
    both in that group? Now the question is, "with what?".

    The markings are : 7839, VM 08. The mfg symbol is a sylized V (kind of like
    \') in a circle or it could be an A if the printed markings like 7839 are
    not necessarily an indicator of what is right-side up. I read somewhere that
    they may be half-wave rectifiers. They look more like IC's than full wave
    rectifiers with the terminals coming out the side and down like spider legs,
    and somewhat rectangular. The PC board calls them BR201, 2 and 3.

    I have searched Google for 7839 bridge rectifier and came up empty. Sorry I
    am not up on my rectifier specs. Thanks,

    Lar
     
  4. Larry B

    Larry B Guest

    Oh, I neglected to mention that there is also a little beige diode marked
    ITT (D202 on the PC baord) that is connected to the cap on the same (-) leg
    that the BR was. Its smaller that the standard looking black diode next to
    it.

    If you suggest its replacement, any suggestions on a spec?

    Thanks, Lar
     
  5. Andy Cuffe

    Andy Cuffe Guest


    Why don't you swap the good electronics onto the good chrome? The
    glass touch panel and all the electronics come off as a single unit.
    Andy Cuffe
     
  6. Larry B

    Larry B Guest

    I was hoping to do just that except that the second unit is actually an
    RR-10A. Everything interfaces the same but the module is a whole different
    animal inside. Same basic individual parts but the layout, boards, etc are
    all different. The touchpad is similar ("orangier" pads), mounting holes,
    9-pin connector and switches are the same but it ends there. Thanks for your
    thoughts.

    Lar
     
  7. Bill Jeffrey

    Bill Jeffrey Guest

    Larry -

    Since your oven was new in 1979, it may be that 7839 is a date code -
    39th week of 1978. How many leads on this beastie? I would expect a
    full-wave bridge to have 4 leads, and a half-wave to have 3.

    Bill
     
  8. Larry B

    Larry B Guest

    :Hi Bill, it has 4 so it must be full-wave. In cruising some parts websites
    a popular spec is DB104.

    Lar
     
  9. Larry B

    Larry B Guest

    Without knowing much about such things, could the cutoff switch failure
    cause a surge that could harm the module's power supply. Typically, what
    part fails in a downstream power supply in such a situation?
     
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