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11-13-2018, 06:08 AM
hodgey hodgey is offline
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There is some high-frequency noise pattern on the output from this VCR on the S-Video output. It's not really noticeable when using composite, though that may be due to high frequencies being filtered out by the Y/C separation in the capture device. The brightness/video levels are also higher than they should be, I can adjust them a bit with the PB Y and Y Gain pots/trimmers on the circuit board, but that doesn't seem to properly solve it, so suspect this may be related to the noise issues. Hi-FI Audio playback is normal, so I presume it's not a head problem.
AG5700_1.png
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It does look like there has been some repair work of some sort done on the circuit board, I don't know if it could be related.
AG5700_2.png


I know this isn't really a great VCR or anything, though it does seem to have some relation to the NV-FS88/FS200 decks. Judging by thespare part list in this thread it uses the same head drum and mechanism.


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01-28-2020, 05:25 PM
hodgey hodgey is offline
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Thought I'd update this, in case anyone else has issues with these.

I recently tried replacing the SMD caps in the delay line unit. None of them seemed to have leaked thankfully, but some of the ones I managed to measure had high ESR. After doing that the high-frequency-noise is gone. The unit in question seems to have a different delay line board (and head drum) than what the service manual I could find lists. The SM lists a CCD PCB with a single CCD delay line chip that is pretty much identical to the one in the Panasonic FS88/FS200 and AG7350 units. This one instead has a digital delay line (A/D chip + memory + D/A chip) instead, including bodge wires you can see in the picture I posted going over the pcb.

Interestingly, the datasheet (HM63021) for the Memory chip used also mentions using it as part of a TBC as a use case.

Going to replace power supply caps next and see if that further reduces other noise, but the picture is already looking pretty nice.
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