Panasonic NV-HS10 noise lines during play

[Tokyo_DIY]

I am trying to repair a Panasonic NV-HS10 NTSC S-VHS machine (produced in 2000).
This machine loads correctly the tape, can do FF and REW correctly, and it seems to me that mechanically it behaves normally.
However normal PLAY produces all the time a picture like the one in the attachments. The tape is not being played faster than normal: at least, as far as I can understand the speed looks normal to me (the counter advances 1 s per second). Color is present. Audio appears very noisy/broken, but at the correct speed).

I was suspecting a tape path alignment issue, but even trying to adjust the tape guides, the situation did not change, so it must be something else.
The pictures are from a SP tape, but also a EP tape gives the same result.

[timtape]

From the photos it looks like one of the two interlaced video fields is missing. I would first check that the video heads are clean. Just one tiny speck of dirt on a tiny video head is enough to block the signal. It affects every make and model. A VCR is only as good as its state of maintenance at this moment.

[Tokyo_DIY]

Quote:

Originally Posted by timtape

From the photos it looks like one of the two interlaced video fields is missing. I would first check that the video heads are clean. Just one tiny speck of dirt on a tiny video head is enough to block the signal. It affects every make and model. A VCR is only as good as its state of maintenance at this moment.

I would expect that if one field is missing every other scan line should be missing. I am not sure, but this one looks like a slightly different case to me.

By the way, let me add a photo of how the picture looks like in PAUSE.

Thank you.

[hodgey]

Are you sure that the mechanical part is okay? I've seen something a bit like this on a video8 camcorder when one of the tape guides were missing. It looks like the heads is moving over multiple tracks on the video tape.

[latreche34]

The VCR is severly miss aligned and you probably made it worst by now. You can't just turn those guides, you have to know which one needs adjustement first, the exit guide or the entrance guide, once one is adjusted then the second one can be adjusted, the process can repeat several times for fine tuning.

[Tokyo_DIY]

Quote:

Originally Posted by hodgey

Are you sure that the mechanical part is okay? I've seen something a bit like this on a video8 camcorder when one of the tape guides were missing. It looks like the heads is moving over multiple tracks on the video tape.

Thank you hodgey,
all the guides seem to be in place.
I have compared the HS10 and the deck in
https://www.youtube.com/watch?v=M2rm7OEk1zc&t=104s
which seems to have the same Z mechanism, and they have the same guide components. If you have time, you can check the 2 pictures and compare as well.

[Tokyo_DIY]

Quote:

Originally Posted by latreche34

The VCR is severly miss aligned and you probably made it worst by now. You can't just turn those guides, you have to know which one needs adjustement first, the exit guide or the entrance guide, once one is adjusted then the second one can be adjusted, the process can repeat several times for fine tuning.

Hi latreche34,
thank you for hinting at guide alignment.
After trying to adjust the guides height, I have put them back to the original position (which I had memorized).

[Tokyo_DIY]

Actually, after looking more carefully at what happens inside the deck during PLAY, I observed that the two tape guides do not move fully forward into play position.
So, as you can see from the attachment to this post, the tape is not fully wound around the drum.

Does anybody happen to know when this kind of issue normally happens? Please note that just in case I have cleaned the inside of the mode switch, so now the operations of load, eject, FFWD, REW work really smoothly and without delays. However the guides do not move fully into play position.
Your comments and suggestions are very welcome.

[Dougmc]

I never work.on that unit
The arms may be spring loaded so maybe one of the assemblies is catching
On something. might try to push them farther.
Those levers ride in a groove in the main cam maybe the groove is broke.
Is the mode switch timed correctly with the cam gear?

[Tokyo_DIY]

Quote:

Originally Posted by Dougmc

I never work.on that unit
The arms may be spring loaded so maybe one of the assemblies is catching
On something. might try to push them farther.
Those levers ride in a groove in the main cam maybe the groove is broke.
Is the mode switch timed correctly with the cam gear?

Yes, the rotary encoder should be in the correct phase relative to the cam gear.

I have found that the complete disassemble procedure for this exact mechanism is covered in the following video:
https://youtu.be/4tVtHUjRGTM?t=1151
so maybe I can try to disassemble the central part of the mechanism and check what is the cause for the slides not to go fully into position.

[Dougmc]

That great you found the video.
I see there is a metal gear driving the plastic gear for the guide posts.
I would guess the gear teeth on the plastic gear are bad.

[Tokyo_DIY]

Quote:

Originally Posted by Dougmc

That great you found the video.
I see there is a metal gear driving the plastic gear for the guide posts.
I would guess the gear teeth on the plastic gear are bad.

Yes, unfortunately it is possible that the gear teeth are bad, and in that case I may be unable to complete successfully the repair.
I will carry out the disassembly this coming Saturday and will post the result.
Many thanks.

[Dougmc]

Also that gear has the tension spring in it.
Maybe the tab of the spring came loose from the nylon gear. If the nylon gear is broke where
The spring tab hole, make repair with a screw?
Good luck this weekend

[hodgey]

You can find a service manual for the mechanism here. If something is broken you may be able to salvage parts of a cheap deck. Panasonic used the same mechanism for the cheaper models released around the same time (only difference I know is that on the SVHS ones the left tape guide is made of brass). The head amplifier and drum setup varied a bit too over the years, but the base mech is the same. The exception being in the US where most consumer panasonic vcrs at the time used a completely different mechanism and design, though there were still some that have it, including some "commercial" ones.

[Tokyo_DIY]

Quote:

Originally Posted by Dougmc

That great you found the video.
I see there is a metal gear driving the plastic gear for the guide posts.
I would guess the gear teeth on the plastic gear are bad.

Yes, the problem is exactly where the metal gear drives the plastic gear.
I had to tear down the whole mechanism, but in the end I could see that the issue is in the area of the red circle in the first of the 2 photos attached here.
The second photo shows that there are 2 partially missing (broken or worn out) teeth in the plastic gear.

[latreche34]

https://www.ebay.com/itm/133546647050?hash=item1f18001e0a:g:tDIAAOSwxfhepEn 3

[Dougmc]

Thanks for posting that info latreche34
I didn't get that site to work but the item number in it
133546647050 works in ebay search
Ships from Germany.

[latreche34]

Sorry, The forum screwed up the link: Another try.

[Tokyo_DIY]

Quote:

Originally Posted by latreche34

Sorry, The forum screwed up the link: Another try.

Many thanks for sharing this info.
I am considering a bit what is the most economical thing to do. I have bought the VCR itself with all accessories included for 2700JPY, and this pair of gears on eBay costs basically the same if you include the shipping to Japan

In Japan there are plenty of old vcrs that you can buy for the equivalent of 5 ~ 15USD, so let me check a bit among used/junk stuff.

[timtape]

Important also to work out what caused the gears to fail. Otherwise the new gears may fail in the same way.