Panasonic NV-FS90A video issues, audio fine?

[OldAT]

Hey Folks

I've acquired a Panasonic NV-FS90A which seems to have video playback issues on all tapes. Audio does however seem to work just fine.

I've gone through the power supply and replaced all the capacitors including the C09 - 400V 1uF which from my research is usually the culprit but no luck so far. I have also carefully given the heads a clean.

I've uploaded a short video here of the output I'm receiving https://youtu.be/cTLlPcYd9_g .

Any advice on where I should check/replace from here would be brilliant. Thanks!

[hodgey]

Looks more like something that would be caused bad caps in the video section. I don't know what the exact cap would be but the Panasonics SVHS decks from this era are known to have some caps on the video boards that go bad over time if you look up this and other ones from the early 90s like the FS100.

[OldAT]

Quote:

this era are known to have some caps on the video boards that go bad over time

Thanks for the tip on the video board. I took at look at the service manual but I'm not sure which one it would be, first thoughts are the IO Pack CBA but Im not sure, I'll attach the layout diagram:

[BartoloniDavy]

leaving the unit powered after 1 or 2 hours there is a small improvement on the image?

[hodgey]

Quote:

Originally Posted by OldAT

Thanks for the tip on the video board. I took at look at the service manual but I'm not sure which one it would be, first thoughts are the IO Pack CBA but Im not sure, I'll attach the layout diagram:

I think Luma/chroma pack or HQ pack. In particular the capacitors in the 1H delay line CCD module that's has metal shielding around it seems to be an issue according to attached doc. (Seems to be an issue on several of the models from this time) Also SMD caps on Hybrid IC for SVHS playback specifically.

[OldAT]

Quote:

Originally Posted by hodgey

I think Luma/chroma pack or HQ pack. In particular the capacitors in the 1H delay line CCD module that's has metal shielding around it seems to be an issue according to attached doc. (Seems to be an issue on several of the models from this time) Also SMD caps on Hybrid IC for SVHS playback specifically.

So I removed that board, a bunch of caps are reading high ESR and the C1 seems to be dead, Ill get the new parts ordered and report back once I've recapped it. Thanks!

[OldAT]

Update is good, I recapped that board completely in the end, and the picture was perfect,,,, for the first capture. I realised I needed to change some software settings (not on the vcr) and now there's some horizontal lines that flicker every now and then. I tried multiple tapes to eliminate that but its the same. Adjusting tracking makes it worse, this is the cleanest I could get it.

I'm assuming/hoping another cap somewhere has kicked the bucket?

Video: https://youtu.be/TR2wotL56bM

[timtape]

It looks a bit like the dropout compensator is not working as it should. Maybe a cap in that area is tired or the new one was reversed when fitted.

[OldAT]

So I went back to the problems pdf shared above and saw the line item:

Quote:

Panasonic NVFS90 INT FINE HORIZONTAL PATTERNING C3311 10uF 16v OC IN HQ CCT

I pulled that board and found a number of bad 16v 10uf caps and swapped them out. Good as new!

My remaining problem is I can't Stop and Rewind/Fast Forward the tape, it seems to clunk around, try to eject the tape and then start playing again but that's not a deal breaker as I can slow rewind if needed or use a different player to rewind fully.

[timtape]

This from the same "Problems" list:

"Panasonic NVFS90 : Bad drop out or fine hor patt In pback : C3311 10µ o/c in HQ pack"

This symptom "bad drop out or fine hor pattern in pback" more closely resembles that in your video sample. It's also the same cap causing it.

[OldAT]

Quote:

This symptom "bad drop out or fine hor pattern in pback" more closely resembles that in your video sample. It's also the same cap causing it.

Ah there you go, probably comes down to my mis-understanding of the issue. Thanks for clarifying.

[timtape]

You're welcome. It's more identifying the issue visually. Here's a still frame from your YT upload at around 4 seconds in. I've highlighted the general horizontal band in green and the fine lines circled in red. This seemed to me dropout compensation territory and what the "Problems" pdf refers to as "bad drop out or fine horizontal pattern in playback.

Look up "dropout compensation", or "dropout compensator" (DOC) to understand exactly what it does and why in analog videotape playback.

[aramkolt]

Seems that a lot of VCRs I've played around with have less than ideal DOC (dropout compensation). How do you narrow down which caps on a specific VCR are directly related to DOC for potential swap out?

[timtape]

I guess as here we could do worse than look for any fault finding helps in VCR service manuals. The advice was successful in this case.