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Magnavox 42MF521D/37B

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  • selldoor
    replied
    Re: Magnavox 42MF521D/37B

    Did you miss Tom's post where he said it could be the startup cap?

    Leave a comment:


  • junktv
    replied
    Re: Magnavox 42MF521D/37B

    Following a test that Plainbill suggested in another thread on one of these i came up with a low voltage and fluctuating readings.

    https://www.badcaps.net/forum/showpo...2&postcount=13

    DC1 19-23v
    DC2 20v

    In the 2nd pic it shows the voltage for the inverters. Should i be getting any reading on the middle 2 pins?

    I'm not sure what i should be getting on the pinout for the logic board or what is what. The wires alternate red/white/red/white etc so I didn't poke around there.
    Attached Files

    Leave a comment:


  • junktv
    replied
    Re: Magnavox 42MF521D/37B

    That is flux that was on there and the pic. Some joints did have a bit too much solder and those pics are from before i capped it.

    The fuse was the first thing i checked.

    Leave a comment:


  • selldoor
    replied
    Re: Magnavox 42MF521D/37B

    No didnt mean that - see attachments I meant the red circled bit in reflow2
    In reflow I have marked in red something which looks a bit burnt - is it just the pic.? I have also ringed joints in pink on both that could probably do with
    re touching but again it could just be the pic.

    EDIT

    If the back light doesnt come on at all have you tested the white block fuse on the inverter board.
    Attached Files
    Last edited by selldoor; 05-30-2012, 07:42 AM. Reason: fuse

    Leave a comment:


  • tom66
    replied
    Re: Magnavox 42MF521D/37B

    Originally posted by junktv View Post
    They were all bouncing from 15-23v except the out side red on wire on the left inverter.
    This indicates a bad startup cap usually - on the primary, a small cap 10uF to 47uF.

    Leave a comment:


  • junktv
    replied
    Re: Magnavox 42MF521D/37B

    They were all bouncing from 15-23v except the out side red on wire on the left inverter. It was dead.
    Last edited by junktv; 05-30-2012, 07:23 AM.

    Leave a comment:


  • tom66
    replied
    Re: Magnavox 42MF521D/37B

    Originally posted by junktv View Post
    Where do i check that? DC?

    Here are pics of one of the inverters.
    DC 200V range. Test the red and black wires. It might be easier to test it at the inverter plug.

    Leave a comment:


  • junktv
    replied
    Re: Magnavox 42MF521D/37B

    Originally posted by selldoor View Post
    As you say pics are not great however can you look near pin 11? on the big transformer
    there is something doesnt look quite right as though it might be shorting/arcing.
    Yes 11/12 on both plugs are bridged. Looks like it is supposed to be there.
    Attached Files
    Last edited by junktv; 05-30-2012, 06:07 AM.

    Leave a comment:


  • junktv
    replied
    Re: Magnavox 42MF521D/37B

    Where do i check that? DC?

    Here are pics of one of the inverters.
    Attached Files

    Leave a comment:


  • selldoor
    replied
    Re: Magnavox 42MF521D/37B

    As you say pics are not great however can you look near pin 11? on the big transformer
    there is something doesnt look quite right as though it might be shorting/arcing.

    Leave a comment:


  • tom66
    replied
    Re: Magnavox 42MF521D/37B

    Check you're getting a good +24V going to the inverters.

    Leave a comment:


  • junktv
    replied
    Re: Magnavox 42MF521D/37B

    Well i tried it and at first the power button lit up and got bright staying on like it should when working fine but the screen never lit up. I turned it off and realised i forgot to plug in the left inverter. So i unplugged it, let it sit for a bit and plugged in the inverter to try again. This time it acted like it did originally where the power light blinks and won't shut off after being pressed.

    Sorry for the bad pics, all i have is a cell camera.
    Attached Files

    Leave a comment:


  • junktv
    replied
    Re: Magnavox 42MF521D/37B

    Just checking for a manual again incase someone has one that wasn't on last week.

    I have the new caps in now just haven't tried it. To clarify post #6 i tested the diodes still in the board.

    Tom66, I'll get some pics tomorrow before i try it.

    Thanks

    Leave a comment:


  • junktv
    replied
    Re: Magnavox 42MF521D/37B

    Originally posted by retiredcaps View Post
    This power board probably has the same suspect diodes 6054, 6055, and 6056 as the Philips models.


    All diodes seem to read one way but some do climb. Those you listed are 500-600 and steady.
    The frame does have a LG.Phillips sticker.

    Leave a comment:


  • retiredcaps
    replied
    Re: Magnavox 42MF521D/37B

    This power board probably has the same suspect diodes 6054, 6055, and 6056 as the Philips models.

    Leave a comment:


  • tom66
    replied
    Re: Magnavox 42MF521D/37B

    Originally posted by junktv View Post
    I looked also and this board isn't labeled for + and gnd.
    Can you post a pic of around the connector going to the main board, and going to the inverter?

    Leave a comment:


  • junktv
    replied
    Re: Magnavox 42MF521D/37B

    I looked also and this board isn't labeled for + and gnd.

    Leave a comment:


  • tom66
    replied
    Re: Magnavox 42MF521D/37B

    Both of those caps are suitable replacements.

    If you have a digital multimeter, you can check if the PSU outputs are in spec - if the caps are bad, they will usually read low.

    No luck finding a service manual on my favourite sites.

    Leave a comment:


  • junktv
    started a topic Magnavox 42MF521D/37B

    Magnavox 42MF521D/37B

    Anyone have a service manual for one of these?

    Trying to see if I can fix this for a friend of the family. Symptoms are a steady flashing power button after it is pushed with no picture or sound. Has the normal bad caps and seems the diodes check out.

    I was able to find the spec sheet for the capxon gf caps so have 1 P12384-ND and 3 P12409-ND for replacements in the cart.
    Attached Files
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