Panasonic NV FS200 black lines problem?

[pthebest19]

Hi everyone. I recently got a Blaupunkt clone of the NV FS200 for a very good price. But when I tried playing tapes with it I noticed the playback having black horizontal lines showing on screen.

I attached a video as well as a picture to give you the idea.

To be fair inside it was pretty dirty. There was some oxide shedding too, even though nowhere as critical as what I've seen in this post: http://www.digitalfaq.com/forum/vcr-...dust-hair.html

Even after I cleaned it the problem is still there. I'm not sure if it's how these units play back VHS tapes or it's mine being faulty.

I'm tempted to try out the NV HS950 model too once I find a good deal.

[latreche34]

Tape drop outs, there is nothing you can do about it, It's an analog recording format, it has its drawbacks especially after 2 or 3 decades.

[hodgey]

It is dropouts, though they're not supposed to be quite as dark. The YNR balance trimpot needs to be adjusted a bit it looks like, it controls the gain of the signal that's used for dropout correction (and noise reduction.) Page 70, "2-3-11 Luminance noise reduction balance adjustment" here. If it's off the areas where the VCR replaces the video signal with the signal from the previous line to mask dropouts will look too dark or bright. Newer VCRs used some sort of automatic gain control for it but on older decks like this it's adjusted manually and at least in my experience it's common that it has drifted a bit due to the age of these decks and needs to be adjusted. The procedure used in the SM uses an oscilloscope + a temporary capacitor though you can get pretty close by eyeballing it on a tape with a lot of dropouts (make sure to look at dropouts in both dark and bright areas of the image!). Annoyingly though adjustment pot can be a bit hard to access at the same time as playing the Panasonics on these era as they were kinda designed to be serviced by connecting the smaller PCBs with some special unobtainium extension cables rather than being easily accessible from the top.

[pthebest19]

@hodgey I found an older post about the same issue: http://www.digitalfaq.com/forum/vcr-...nv-hs1000.html

Is this the trimpot I need to adjust? Last day I tried to lift the main board but didn't succeed, I need more time.

[hodgey]

Yeah it's the same issue on the newer NV-HS1000. Probably won't be in the same spot but should be on the luminance/chrominance pcb. I haven't used the FS200, though at least on it's little non-vhs brother the NV-F77, and the nv-hs1000 you have to unscrew and lift up the main PCB. It should be possible to flip it over and put it on top of the mechanism with something insulating in between, or on it's side when adjusting. I believe there are other people who have worked on this vcr (though maybe not with this specific issue) that can give pointers if it's tricky.

Idk why the vcrs of the time were designed with the boards "upside down" like this which makes it annoying to work on, but it seems to have been a common approach across different manucaturers.

This video is of the US equivialent AG-1970P which is like 90% the same, you can see the linked time how the guy has put the pcb while working: https://youtu.be/bYzVgr_B3l4?t=1005, also shown in the manual I think.

The adjustment will be on the luminance/chrominance sub-board:

fs200 adjustment.jpg

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[pthebest19]

I’ll give it a try as soon I have some time.

But also I have another question. I noticed during playback there’s some sort of ringing effect, and even if I tone down the sharpness it’s still there. Is that normal?

[hodgey]

Added some images in my prev post.

Depends what you mean by ringing, there are some capacitors on the video board(s) (or see e.g page 67 here NV-FS88) that tend to go bad and can cause some noise/patterning on the output if that's what you mean.

In a video I'm working about of overview/repair of a Fisher VCR there will be a bit showing the same adjustment on that VCR (though the pot is a bit more accessible on that one.) Adjusting by eye is basically playing a tape with lots of dropouts and carefully tweaking it so the dropouts are neither too bright or too dark.

[pthebest19]

I attached 2 pictures. The first is with the NV FS200, the second with the NV SV120 (wrong aspect ratio I know).

[hodgey]

Not seeing any standout ringing on the FS200, just differences in de-emphasis and sharpness amounts between the VCRs. The SV120 has a sharper dark->bright transition but also more ringing after the bright->dark transition (e.g behind the letters.)