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  1. Hi!
    I have a JVC KM-F250 TBC that output black when active (through the "operate" switch) with the "low video level" light on. This doesn't happen when it's not active (in bypass mode). As suggested by the manual (https://www.adcom.it/public/images/Manual/KM-F250%20MAN%20ENG.pdf, page 9) I tried to increase video level with the trimmer but the output stays black with the "low level" light always on.
    Can anyone help me?
    Thank you in anticipation
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  2. I have same problem. Some youtuber told me it's a power supply issue but I'm not technical enough to diagnose it. The power supply is not supplying all the different voltages 5V, -5V, 12V, -12V.
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  3. Video Restorer lordsmurf's Avatar
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    Old post, but still causing confusion.

    This unit is not a TBC. It is a mere frame sync, with a genlock, and freeze frame. None of that is a TBC. The "timing" it does is to phase match chroma and luma, to prevent chroma ghosting, maybe bleed.

    There is a video on Youtube showing ... something (line TBC?). But even the "fixed" image shows massive breaking in the image, it's not stable. If a test pattern cannot stay stable, actual footage stands no chance.

    This is an ancient broadcast devices created for linear editing (realtime analog live editing, ie not NLE), or duplication. It vastly predates the gear we all need for successful analog>digital conversion.
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  4. Capturing Memories dellsam34's Avatar
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    From the manual linked it does look like a 1MB memory full frame/field TBC with ability to synchronize with other equipment. Though, 1MB is not that big for a lossless 10bit frame, my guess is probably 6 or 8bit and less than 4:2:2. It is PAL only with the option to output the pseudo NTSC (NTSC 4.43).

    OP, make sure it is receiving a PAL signal.
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  5. Originally Posted by lordsmurf View Post
    Old post, but still causing confusion.

    This unit is not a TBC. It is a mere frame sync, with a genlock, and freeze frame. None of that is a TBC. The "timing" it does is to phase match chroma and luma, to prevent chroma ghosting, maybe bleed.

    There is a video on Youtube showing ... something (line TBC?). But even the "fixed" image shows massive breaking in the image, it's not stable. If a test pattern cannot stay stable, actual footage stands no chance.

    This is an ancient broadcast devices created for linear editing (realtime analog live editing, ie not NLE), or duplication. It vastly predates the gear we all need for successful analog>digital conversion.
    My plan is to fix the unit sooner or later (if it's really a PSU problem it should be not so hard...). I really want to test it. I think it's a TBC "specific" for Umatic input (the DUB -> S-Video feature is what made me buy this), so maybe it's not "strong" as much as needed to correct error-prone sources like VHS but effective on more stable sources like Umatic.


    Originally Posted by dellsam34 View Post
    OP, make sure it is receiving a PAL signal.
    I don't remember much of when I was testing this unit, but for sure I was feeding in a PAL signal (I don't have any equipment to produce NTSC output...):
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  6. Originally Posted by lordsmurf View Post
    Old post, but still causing confusion.

    This unit is not a TBC. It is a mere frame sync, with a genlock, and freeze frame. None of that is a TBC. The "timing" it does is to phase match chroma and luma, to prevent chroma ghosting, maybe bleed.

    There is a video on Youtube showing ... something (line TBC?). But even the "fixed" image shows massive breaking in the image, it's not stable. If a test pattern cannot stay stable, actual footage stands no chance.

    This is an ancient broadcast devices created for linear editing (realtime analog live editing, ie not NLE), or duplication. It vastly predates the gear we all need for successful analog>digital conversion.
    I beg to differ, I'd refer to numerous pages within: https://www.adcom.it/public/images/Manual/KM-F250%20MAN%20ENG.pdf

    Pages 2,4,5,6,8 & 10 designate functions indicative of a 'Frame TBC'. You as well as anyone should know that "Frame Synchronizer" is quite frequently used as a synonym for a 'Frame TBC'. Or, in this particular case, a unit noted numerous times as having one integrated - with a varying array of additional features.

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    For the hell of it, including some other links since there is very marginal traces on the internet of this thing ever even having existed:

    https://www.next-archive.com/product/jvc-km-f250e/
    https://www.bcs.tv/store/model_detail.cfm?id=7814
    https://www.digitalfaq.com/forum/video-workflows/10026-how-many-vcr.html (no dispute from you as its efficacy as a TBC)
    https://forum.blackmagicdesign.com/viewtopic.php?f=18&t=56262 (isn't touted as a pure TBC, but fully functional as one in addition to other uses)
    https://www.kleinanzeigen.de/s-anzeige/jvc-km-f250-frame-synchronizer/2487020172-175-3447
    https://modwiggler.com/forum/viewtopic.php?start=20&t=60583
    https://www.likesx.com/jvc-km-f250-tbc/ ("Full Frame time base correction")
    https://esupermk.live/product_details/16235447.html


    ----------------------------------------

    It's a time base corrector, a full-frame one at that. I also absolutely concede it isn't the unit's sole, dedicated purpose.
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  7. Video Restorer lordsmurf's Avatar
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    Originally Posted by SuppaMan View Post
    "specific" for Umatic input
    Now that might be the case.

    Originally Posted by kitty666cats View Post
    I beg to differ,
    No.
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