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Old 21st Jul 2020, 5:58 pm   #1
enryfox
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Default Help with fixing an old Panasonic NV-G10 VCR

Back in 1986 my family bought this Panasonic NV-G10 and now I'm trying to restore it to a fully functional state. So far it is working OK, the only problem I have is with fast forward during playback: speed is not consistent and I do not get the usual two lines of disturbance at 1/3 and 2/3 of the screen. More annoyingly, when I want to resume playback, the tape often halts and the VCR goes in stop state. Pressing play, playback resume with no problem.

What I have done so far:

1) replaced both belts
2) replaced idler tire
3) deep cleaning of tape path
4) cleaning of back tension felt brake.

I have tried the following experiment: during playback I press FFW for 10 seconds and then release it; if playback does not resume I unplug the mains so that it all freezes. I then try to pull the tape with my fingers in an area close to the audio head and the tape appears to be stuck to the head drum. It requires a considerable amount of force to unstick the tape so that playback can resume. That does not happen if I freeze frame during playback, and try to pull the tape: it comes gently with only the back tension of the supply reel.

The same does not happens with REW during playback, speed is consistent and it resume playback with no issue.

Any idea of what might be causing that problem ?

No matter how much I clean the head drum, the problem regularly appears. Please note that the head drum always keep spinning, so the tape appears to stick to the fixed head mount.

regards
Enrico
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Old 21st Jul 2020, 11:48 pm   #2
nickdoofah
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Default Re: Help with fixing an old Panasonic NV-G10 VCR

It sounds like the lower drum is worn out! This was common back then with certain machines - I would think that someone (Poss even here) may have a second hand lower drum assy!
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Old 22nd Jul 2020, 11:11 am   #3
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Default Re: Help with fixing an old Panasonic NV-G10 VCR

Agreed. The problem was aggravated by the fact the back tension was set far too high at the factory - or at least drifted. We always had to back it off to around half of its measured setting. I'd back off the back tension on your machine and you may well find the picture's OK in playback and the tape doesn't drag as much. Worth a go - and keep polishing the lower drum! However once it's lost its shine there's not much you can do.
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Old 22nd Jul 2020, 12:08 pm   #4
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Default Re: Help with fixing an old Panasonic NV-G10 VCR

Duraglit can help in some cases.
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Old 22nd Jul 2020, 2:02 pm   #5
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Default Re: Help with fixing an old Panasonic NV-G10 VCR

Thanks for the replies; I have already eased the back tension by inserting a small ring between the spring attachment on the chassis and the spring hook. Spring stretching is reduced by 4~5 mm compared to factory settings. That has mitigated the problem somehow.

The lower drum appears fine (refer to pictures .. disregards the debris on the right, I cleaned them after the picture was taken) but even to the touch it is not as slippery as I would expect it to be. I cleaned it with IPO and acetone but it did not change much.

Playback is fine, drag is not excessive; it's just a restoration for fun, I do not plan on using it on a regular basis. I could try polishing the lower drum with brasso or similar, but I'm afraid in further disassembling the unit as something else might brake definitely.

Any suggestion on solvent I could use without taking it apart ?

As a side note: dragging seems aggravated when the head drum is warm as as a result of the drum heater, is that expected ?

thanks
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Old 22nd Jul 2020, 5:23 pm   #6
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Default Re: Help with fixing an old Panasonic NV-G10 VCR

Even the upper drum looks very worn, which is typical in Panasonic machines of this age. Try metal polish and see if that will restore the surface of the drum to some degree. I have a scrapped NV-G10 and the drum is still intact but I don't know the condition of it at the moment. I can give it away if you need it.

Fivos
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Old 22nd Jul 2020, 6:38 pm   #7
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Default Re: Help with fixing an old Panasonic NV-G10 VCR

Thanks for your kind offer, but it is just a fun project, I'd like to restore it as
a family memorabilia, and after 34 years I'm surprised it still works with basically just a new set of belts and a new tyre.

I think the head drum looks worse than it actually is: playback does not show any sign of worn heads; I have a newer Samsung VCR (which saw very little use) and the same cassette plays almost identical on both. After all the Panasonic has been in service between 1986 and 2001 but saw limited use as we did not frequently record or rent movies. When I shelved it for a more recent VCR it was still 100% functional, so whatever happened it was mostly caused by 19 years of storage.

I would like to try metal polish, but how to avoid clogging the heads ?

thanks
bye
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Old 23rd Jul 2020, 10:07 am   #8
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Default Re: Help with fixing an old Panasonic NV-G10 VCR

Looks like it's already had a replacement upper drum. You need to be careful with metal polish as it can get into the heads and do damge as you suggest. Removing the upper drum and polishing the lower drum would be the best option - the whole assembly isn't hard to remove. However as it's working you might just want to live with it especially as the improvement isn't all that great after polishing.
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Old 23rd Jul 2020, 8:17 pm   #9
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Default Re: Help with fixing an old Panasonic NV-G10 VCR

Quote:
Originally Posted by Welsh Anorak View Post
Removing the upper drum and polishing the lower drum would be the best option - the whole assembly isn't hard to remove. However as it's working you might just want to live with it especially as the improvement isn't all that great after polishing.
The upper head drum is hold in place by two screws and ~8 solder joints. If the heads were broken I would surely try to remove it, but as it is mostly working I'm afraid to make it worse.

Thanks for the info and confirmation.

As a side note, the thermal design of this VCR is terrible: the PCB was designed with serviceability in mind (and that's a nice touch) but it is basically a heat trap. The power supply regulator and the capstan motor IC's get pretty hot and they indeed have decent heatsinks; but they are mounted upside down with the PCB blocking any airflow. The only way heat can get out is by irradiation: the hot air trapped below the PCB heats up the PCB itself which in turn heats up the metal cover which then dissipates the heat in the outside air. Very inefficient.
The rectifier diodes are close to the transformer and get pretty hot too, but no heat sink is provided; fortunately at least the metal cover has some grille to let the hot air out. Also, as usual with power supply design of the 80's, there are a couple of resistors used to step down voltages (in my case by ~ 10V) and they get pretty hot (you can see the browned PCB around).
I know that as it still working, maybe the design was sound; but by today's standard, it is quite terrible and inefficient.
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Old 23rd Jul 2020, 10:35 pm   #10
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Default Re: Help with fixing an old Panasonic NV-G10 VCR

Hi.

I remember having a few problems with tape grabbing on the lower drum assembly in various VHS machines which seemed to happen in high mileage machines. The original polished alloy finish becomes more dull looking increasing the friction. A reduction in the back tension setting should help, though the still frame facility may not be so good. Reduced back tension will generally help to prolong the life of the video heads (upper drum). Agreed the back tension in some Panasonic decks was often excessive. I used to use my Konig tension cassette for checking. A tentelometer was another way to check it.

When I used to service VCRs it was often frowned upon using head cleaning tapes, the ones that were mildly abrasive in nature. Use of such a cleaning tape couldn't have been good for the drum assembly and tape path in general. No substitute for manually cleaning the heads and tape path with IPA.

Regards,
Symon
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Old 24th Jul 2020, 12:13 pm   #11
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Default Re: Help with fixing an old Panasonic NV-G10 VCR

Exactly - we discouraged the use of cleaning tapes, especailly the wet type. We had a few very conscientious customers who would use a cleaning tape every ten hours of playback thinking they were doing the right thing, only to need upper (and sometimes lower) drum replacement after only a year or so.
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Old 24th Jul 2020, 3:51 pm   #12
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Default Re: Help with fixing an old Panasonic NV-G10 VCR

Yes. You are right about the back-tension setting. I too find it to be very excessive on Panasonic VCRs of this vintage. On some of the Panasonics I've worked on (NV-8600, 7500, 380 etc), sometimes tapes near the end wouldn't even play at the right speed because of the worn drum and the excessive amount of back-tension that caused the tape to stick onto the drum. Keep in mind that reducing the back-tension will often result in flagging/skew error (a time-base error where the picture bends at the top of the screen) on many CRT sets when playing back tapes recorded on machines with a greater back-tension setting.

Fivos
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Old 26th Jul 2020, 7:09 pm   #13
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Default Re: Help with fixing an old Panasonic NV-G10 VCR

After FF or REW during playback tou said that the vcr goes in stop. Are you sure that the idler and the clutch are OK. Worn head does not create this error
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Old 26th Jul 2020, 7:26 pm   #14
enryfox
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Default Re: Help with fixing an old Panasonic NV-G10 VCR

The idler is ok, I just replaced its tyre and it works ok; the problem is the tape sticking to the lower drum during scan forward: I see the capstan slipping because the tape is too hard to pull; sometime the tape unstick on its own and playback resume normally, other times (especially when the supply reel is almost empty and back tension is at its max) it goes to stop after few seconds as the reels are not turning.
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Old 26th Jul 2020, 8:38 pm   #15
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Default Re: Help with fixing an old Panasonic NV-G10 VCR

From your description the problem must be related with the gears near the clutch. Check that the plates moved nornally. Probably the grease became sticky due to years. I had the same problem in g12.
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Old 27th Jul 2020, 10:35 am   #16
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Default Re: Help with fixing an old Panasonic NV-G10 VCR

I understood that although FF and REW work fine the problem only happens in picture search and play which points to the drum problem we mentioned above. Is this correct?
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Old 27th Jul 2020, 11:44 am   #17
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Default Re: Help with fixing an old Panasonic NV-G10 VCR

Yes you are correct, I'm not even sure the G10 has indeed a clutch; from what i can see the capstan motor is driving the reels directly with the idler acting as a pendulum and connecting to either the supply or take-up hub based on the direction of rotation.
The take up hub has indeed two brakes: one main brake is engaged when in full stop mode; a secondary smaller brake is engaged only when in playback. That secondary brake make the hub harder to rotate thus decreasing the torque generated by the idler; it is then the idler slipping on the hub to act as a clutch when in playback. When in FF or REW the secondary brake is released and full torque is applied to the hubs.
All tapes movements work perfectly and there is always lot of torque on the hubs; moreover turning by hand the capstan motor I do not feel any resistance and it all moves smoothly.
The problem seems to be the lower drum which lost its shine due to age and maybe use. I can live with that, luckily playback is not affected.
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Old 27th Jul 2020, 12:23 pm   #18
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Default Re: Help with fixing an old Panasonic NV-G10 VCR

As long as you've reduced the back tension, the heads should enjoy a longish life, especially as recording won't be a concern.
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Old 27th Jul 2020, 12:48 pm   #19
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Default Re: Help with fixing an old Panasonic NV-G10 VCR

If you are OK in playback how can the lower drum worn?
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Old 27th Jul 2020, 12:48 pm   #20
enryfox
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Default Re: Help with fixing an old Panasonic NV-G10 VCR

Quote:
Originally Posted by Welsh Anorak View Post
especially as recording won't be a concern.
I would like to check if it still actually records, but I do not have a clean composite video signal at hand. "Modern" flat panel TV's with scart connector do not output any signal and, obviously, the analogue tuner in the VCR is of no use since 2012. I had once a laptop with composite output, but i cannot find it

Anyway, yes, i'm not interested at all in recording...
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