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    VCR debug... playback screen corrupt on bottom?

    I know, these dinosaurs should become gasoline, but still curious on how to fix this.

    I have a cheapo, probably not-worth-to-fix Funai mechanism (Magnavox MWD2206) VCR-DVD combo. When I play back prerecorded VHS tapes, the top ~ 7/8 of the screen looks fine, but the bottom 1/8 is messed up. The bottom 1/8 has no color, and looks like 2/3 of that 1/8 is streaking the bottom most line that does have color (luminance only, no chroma, so it looks like bars) and the bottom most 1/3 looks like it's showing the right luminance for the remainder of the frame, but very noisy and once again no chroma.)

    Other than this it seems to play back almost fine though it occasionally tracks funny.

    Recording seems to work but playing back its own recordings show this same behavior, and playing in other VCRs "works" if it has auto tracking but if you cue/review during play, it's completely messed up.

    I think that for some reason the sync timing is off between the head motor and capstan, but wonder if anyone has seen something like this before?

    Unfortunately the head position sensor is fixed so I can't play with the position of it, at least I don't think I can... It uses a soldered PCB that contains the distribution for the BLDC motor and the detector does not appear to have slide holes - and detects the poles of the BLDC moving magnets much like brushless fans...
    Last edited by eccerr0r; 12-16-2016, 07:26 PM.

    #2
    Re: VCR debug... playback screen corrupt on bottom?

    Two sample images that I recorded on another VCR that I deemed "working"... yes this is the CRT TV I dropped. And no, the problem is not the TV, only this VCR seems to be generating this weirdness on the bottom... The crack in the plastic from the drop can be barely seen on the upper left of the TV...

    https://www.badcaps.net/forum/attach...1&d=1481959135

    https://www.badcaps.net/forum/attach...1&d=1481959135

    Weird eh?
    Attached Files
    Last edited by eccerr0r; 12-17-2016, 01:22 AM.

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      #3
      Re: VCR debug... playback screen corrupt on bottom?

      could still be tracking,
      it's probably a good idea to replace any small caps in the head amp circuit

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        #4
        Re: VCR debug... playback screen corrupt on bottom?

        The head amp? or do you mean the BLDC motor driver?

        It looks like the head circuitry is almost straight connected, with maybe a few resistors and ceramic caps, to the video processor chip. The BLDC motor driver is, well, a single chip solution too, though trying to get at that board has been a pain as price reduction dictated the wiring straps to be mostly soldered...

        Without the remote, adjusting tracking seemed to be impossible - but I found that I could adjust the tracking with the channel keys. Alas it didn't seem to help, it changed the whole frame and not just the bottom.

        This VCR is clearly recording something funny too, not just playback. Though the VCR that I used to test record/play seems to be a "intelligent" vcr and tries to auto-track. (It's a JVC SVHS that I disabled SVHS-ET). IIRC the bottom of the frame looks fine on record when played back on the JVC, just that cue/review is unusable unlike correctly recorded tapes.
        Last edited by eccerr0r; 12-17-2016, 04:36 AM.

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          #5
          Re: VCR debug... playback screen corrupt on bottom?

          If you have not maybe already maybe watch some of this guys vcr video repairs im sure i watched one of his videos with this problem maybe drop him a message with a picture he may respond with a fix for you
          https://www.youtube.com/user/ATVVideoProductions/videos

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