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HELP!!! Maytag Circuit Board

Discussion in 'Troubleshooting and Repair' started by fscii, Jun 12, 2013.

  1. fscii

    fscii

    21
    0
    Nov 13, 2012
    2 Nights ago our power flickered on and off multiple times in a storm and I heard some popping noises. Well the clock on our stove went out (whole board which controls oven, timer etc).

    Calling Maytag got us info that a replacement board is available for $314 shipped. OMG!!!

    The stove is MER7662XX 1 and here's what happened to the board.

    The disc capacitor @ "MOV1" and the resistor R1 are fried. The cap did what caps do - blew apart and I have NO WAY to identify it. Maytag is unhelpful. They tell me they can order me a new board and repairmen basically say the same thing.

    I don't want to pay $314 for a board that just needs a cap. Can someone please help me identify it? Its a big one too. .84" across (21.4mm) and I don't want to just "guess" here and blow something else up.
     
  2. shrtrnd

    shrtrnd

    3,670
    453
    Jan 15, 2010
    That wasn't a cap at 'MOV1', that was an MOV (they just look like caps).
    Metal Oxide Varistor.
    It did what is was supposed to do, absorbed a high voltage spike, unfortunately, the
    spike also destroyed it. You'll have to guess about the resistor, depending on the circuit.
    The MOV is rated for the peak-to-peak voltage of the input voltage. I don't know where
    you're at, so only you know what your mains voltage is.
    It's possible there might be other damage, but it's a pretty-good bet, replacing the MOV
    and it's current limiting resistor that was destroyed, may have saved the rest of the board.
     
  3. fscii

    fscii

    21
    0
    Nov 13, 2012
    Ok thanks! Glad I know what the MOV is now lol. I thought it was a disc cap.

    Well its a 220v oven but 220v doesn't go to the circuit board. I have a schematic for the power system in the oven but im not entirely sure whats' going on. I tried to upload it but it says the 225k or so size is too big to upload.

    How do I know what model MOV to get?
     
  4. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,191
    2,693
    Jan 21, 2010
    If it's a pdf, upload it to a pdf hosting service (google that) and post the link here. If you have the schematic it would be invaluable for us to see.
     
  5. fscii

    fscii

    21
    0
    Nov 13, 2012
    Ok its taken forever but we had to get a new circuit board as the schematic for the stove only showed the circuit board as a part # there was no diagram of the components actually on the circuit board :(

    Still, I'd like to repair the old board as a learning experience (and a spare!) so here's what I saw on the new MOV on the new board:

    1F9 RJ
    P300L40
    1220

    I've been unable to locate that part online or tell what voltage and specs it is anyway. Any ideas guys?
     
  6. fscii

    fscii

    21
    0
    Nov 13, 2012
    Anyone?
     
  7. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    8,393
    1,266
    Nov 28, 2011
    I don't recognise the part number, but then I'm not very familiar with varistors.

    You said in post #3 that your 220V AC mains voltage doesn't go to the board with the varistor on it. That's a little confusing, as a "Bruce" would say. Are you sure about this? Where does the mains voltage go? How does power get to the board? Perhaps you should post the schematic diagram for the stove that you have.

    A few photographs could tell us a lot. Dismantle it as far as getting the board completely out, and take a photo of what you see before you remove each major component, so we can see how it all fits together.

    This can be very helpful. This is probably appropriate for most of the repair questions we get here.

    Also see whether you can trace the tracks from the varistor to a connector. There may be inductors in the path. You can use the continuity test setting on a multimeter, if you have one, to follow the tracks, and follow the connections through the inductors, and see what you can figure out.
     
  8. techiesteve

    techiesteve

    17
    0
    Jul 27, 2013
    I generally use the VA series MOV's, either as direct replacements or as substitutes. For instance the V275LA20P is commonly used with our 230V (actually 240V +) mains supply. Typically a V150LA20P would be used with a 115V mains supply. You can estimate the power handling capacity by the physical size of the disc, or what's left of it. For example, a lower power device would have LA10 in the P/N, higher power LA30.

    You might find this chart useful for choosing a substitute http://docs-europe.electrocomponents.com/webdocs/0785/0900766b80785545.pdf.

    MOV's usually make a loud crack when they fail from a large spike, disintegrating and leaving soot on the adjacent PCB and blow the mains fuse. They should be sleeved in heat shrink tubing before fitting to minimise collateral damage when they fail. Sorry, I can't help with the resistor value unless we know where it is in the circuit, but now you have a replacement board you should be able to determine the burnt resistors value and wattage. Fixing it will give you a spare board in case it was to fail again.
     
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