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DEFY magnetron - stuck with removal?

Discussion in 'Troubleshooting and Repair' started by FuZZ1L0G1C, Jul 18, 2018.

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  1. FuZZ1L0G1C


    Mar 25, 2014
    Yesterday, my DEFY microwave oven model DMO367 MWM 2030W fried its magnetron, and the silver-coated waveguide cover that clips into the cavity inlet slot.
    Beautiful orange corona discharge through the w/g cover, melodious 50 Hz arcing heard, pleasant aroma of burnt ceramic.
    The micros I've worked on in the past had one screw on the magnetron top to remove the light box / cover, the bottom part having a hooked tab that lifts out once top is loose.
    This one, however, has two dome-head star screws, one on top of 700W magnetron, near the mag's thermal cutout, and the other (jammed solid) underneath the magnetron.
    So far, I've managed to loosen the hex-head star screw at R/H side of the mag, but left of mag still stuck.
    Suspect there's another HH star screw hidden behind lightbox cover, securing the magnetron's 'left wing'.
    Has anybody worked on this model or similar type before?
    Do I need to remove the lightbox cover to access a hidden screw?
    Jackhammer, acetylene torch, sledgehammer?? :D
    Thanks, Clive.
    The first time it arced, I had a pie in its aluminium foil dish, both inside the paper packet.
    Didn't check first that metal was present - could it have arced through the paper? (no burns).
    As the magetron arced the second time I tested it, maybe it still works?
    I'm wondering if the burnt oval of silvered ceramic waveguide now creates a short?
    Some mugshots below..
    001 (2).jpg 004.jpg 009.jpg 016.jpg 017.jpg
    Last edited: Jul 18, 2018
  2. 73's de Edd

    73's de Edd

    Aug 21, 2015
    Sir FuZZ1L0G1C . . . . .

    I was hoping to be finding a dimensional drawing of the build of that series of units . . . no findee . . . but this might suffice, instead.
    Photo 1 . . . . .You can see the maggie output probe and its RFI / Grounding mesh and the two RED LINED mounting holes which you are already fully familiar with.

    Photo 2 . . . . You can see the laminar air flow path thru the heat sink fins. The arrows are pointing out the hole patterns in the duplicate Top and Bottom plates

    Photo 3 . . . . Shows the hole patterns . . . . with 18 possibilities of them in having possibly used another set of mounting screws in them . . .which you are wondering about .

    This should give you a guesstimate, as to what area to be expecting any other possible elusive mounting screws, to be hiding in.

    You say . . . .stuck #@%^& ^ SOLID !
    I can't positively see good enough confirm if that is a BRISTOL or TORX screw or possibly the worst case, would be a security TORX due to the limited active depth that they have. Or possibly, that's even being a common hex.
    When I have BAD ones, I usually can succeed in outing them, with the use of a Dremel tool with a mini cut off wheel being used and putting a common slot across the screw head to use a common slotted screwdriver.
    OR I cut flats across each of the sides of the screw head to alter it into a quasi clutchead. Those alternate flats then let me use a set of mini vise-grips to clamp down on it, across those flats on its head, and take it out .

    M24FA-410A . . . . .MAGNETRON PHYSICAL BUILD . . . . .


    Thasssssssssit . . .

    73's de Edd
    Last edited: Jul 19, 2018
    Richard9025 likes this.
  3. kellys_eye


    Jun 25, 2010
    You might need the use of an impact screwdriver to 'shock' the bolt/screw loose but whether you (a) have one or (b) can get it in there to do the job!
  4. FuZZ1L0G1C


    Mar 25, 2014
    Thanks for helpful replies @73's and @kellys.
    Been a bit busy so haven't really tackled it much further yet.
    Using my 45 degree 'tape-head-inspection' mirror, the stuck screw is definitely star-point, but with a domed head profile. As for 'shocking', i'm planning to try a nozzled 2000W heat gun, the 'tin' nozzle concentrater seen on an older post here.
    Just enough heat to expand the screw slightly, then maybe deep-freezer-iced facecloth to quickly contract it.
    Using a webcam as a macro inspection tool, the hidden hexagonal screw for magnetron's left mount is center of left wing, as in ed's photo 1 post#2.
    Thanks again guys. :)
    Last edited: Jul 19, 2018
  5. bushtech


    Sep 13, 2016
    Stick a screwdriver in there and give it a couple of sharp raps with a hammer.
    Can you get a vise gripper in there?
  6. FuZZ1L0G1C


    Mar 25, 2014
    Problem fixed.
    First tried heatgun / ice for thermal shock, then screwdriver whacked with hammer, then vicegrips, which kept jumping off.
    Eventually, the solution was to remove the entire base-plate, which gave me full access to the bottom light-box screw, which a 6mm diameter rubber-handled star screwdriver, gripped with both hands, loosened the screw.
    As it turns out, the magnetron tube and HV diode which the electrical supplier sold me came to just over R300 (ZAR), so a lot cheaper than renewing the micro at R1200(ZAR), which another forum points-hungry member suggested. :/ (ps - not EP)

    Magnetron Power Difference:
    The old magnetron was rated 700W output.
    However, after buying the (non-returnable) new magnetron today, which the salesman said can work on my micro, I researched the make / model number on the internet:
    LG 2M214 06B P01L-16458 (made in China)
    Although the mounting holes align perfectly, the width (for lightbox) is 7mm wider at 80mm than old one.
    After a bit of panel-beating and vice work resized lightbox to fit.
    The power output of the new LG is anything from 900W to 1500W, depending on which website is being viewed.
    Will a higher power output overload the transformer or voltage doubler cap/diode?
    As the supplier has a 'no return' policy on mags tubes, maybe i'll test it anyway - if it fries, I'll get another MW oven.
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