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Old 6th Apr 2018, 2:18 pm   #1
monaro0162
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Default Panasonic NV-870 VHS Video Cassette Recorder (1985)

Found this at a boot sale for £1. Back in the day I had a NV-830B which at the time was one of the first machines that had the HiFi stereo sound track. Great machine used it a lot to record music videos on MTV up until around 1995. This 870 appears to be very similar to the 830 its not quite so tall.

Finally had some time to assess its condition. The list of problems reads like a bad day at the MOT centre:

1-Doesn't load or eject the cassette properly. It requires considerable assistance when loading and needs to be pushed down fully in order to load. On the eject cycle it doesn't push the cassette up fully it needs to be pulled out by hand. The eject motor and gearing is working, the mechanism seems to be getting stuck somewhere.

2-When playing the take up reel appears sticky and sometimes doesn't keep up with the tape coming from the pinch roller.

3-Fast forward - works ok

4-Rewind - rewind motor noises can be heard (uneven) eventually the motor stops

5-Picture - it does actually play although the picture rolls vertically along with tracking noise being visible. Adjusting the tracking control does not make much difference. Occasionally the picture will stabilize and the quality looks ok.

6-sound. The linear sound track is working ok. In HiFi mode, only the right channel seems to be working when it syncs up for long enough. Doesn't seem to be any right channel sound going through the machine when it is in hifi mode, although in linear mode it is working ok so I don't think that the problem is physical connectors.

I would like to get this machine going for nostalgic reasons. I would like to experiment with the HiFi stereo recording capabilities and I have a load of VHS tapes music from the 80's and 90's to review.

Priority is to get the picture tracking sorted out. Where do I start?
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Old 6th Apr 2018, 4:59 pm   #2
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Default Re: Panasonic NV-870 VHS Video Cassette Recorder (1985)

Awsome score! It has the same chassis as my NV-G10, which in my opinion, is the best Panasonic chassis ever made. Very easy to change the belts and the idler. I suspect the bad picture is due to tape path misalignment on the P2 and P3 guides (the ones that wrap the tape around the drum) and that is also probably the reason why the left hi-fi track is bad. Failure to accept the tape is likely dirty/oxidized switch contacts on the front loading mechanism assembly. These caps on the 3rd picture look terrible. But I think these are only there for the timer memory backup in case of power failure.

Fivos
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Old 6th Apr 2018, 7:17 pm   #3
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Default Re: Panasonic NV-870 VHS Video Cassette Recorder (1985)

I would check the back tension band too, the felt band on these tended to fall off, great machines.
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Old 6th Apr 2018, 7:40 pm   #4
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Default Re: Panasonic NV-870 VHS Video Cassette Recorder (1985)

Yes! The back-tension brakes on these old Panasonics always go bad, especially the ones with the copper bands.
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Old 6th Apr 2018, 10:30 pm   #5
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Default Re: Panasonic NV-870 VHS Video Cassette Recorder (1985)

This is the good ol' D deck.
I did one a few years ago.
-For the loading, change the belt on the carriage right and clean /relube the worm gear. the carriage lifts out easily enogh once screws removed.

-Mode switch should always be cleaned or changed. Very common source of probs. I tend to find that the main evidence of this is going from play to review /rewind is erratic.

-Poor rewind (especially on review) is a) the idler tyre and b) the main belt. Change both after cleaning contact surfaces.

-A worn or pitted pinch roller is common on this age of deck and will give the mistracking you mention. Change it. The hi fi will probably work properly once the tape motion is more stable.

-Switch cleaner on all front panel switches for audio.

-Full clean of tape path

-Check backtension band as suggested.

Phew! I really needed a drink after doing the last D deck. They're 30 odd years old now so need a lot of work, but should be fine once sorted.
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Last edited by ben; 6th Apr 2018 at 10:38 pm.
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Old 6th Apr 2018, 10:39 pm   #6
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Default Re: Panasonic NV-870 VHS Video Cassette Recorder (1985)

Hi
You can solve most of the mechanical problems doing the followings:
1. Replace all the belts
2.Replace the idler

Check the tension band it is a common fault due to years that the tension band brake fell off. If you have this problem it is better to replace the tension band but marked with a pencil where the tension band located from the factory.
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Old 7th Apr 2018, 1:16 am   #7
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Default Re: Panasonic NV-870 VHS Video Cassette Recorder (1985)

Hi,

Something in my (not very reliable) memory is telling me that those three memory back up capacitors are of a type whose leakage reacts really rather badly with the heat from a soldering iron. I seem to think they are best cut out, and the board cleaned up before heat is applied.

Regards

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Old 7th Apr 2018, 1:25 am   #8
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Default Re: Panasonic NV-870 VHS Video Cassette Recorder (1985)

You can also get the manual from here:
http://freeservicemanuals.info/en/se...nasonic/NV870/

Fivos
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Old 7th Apr 2018, 3:36 am   #9
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Default Re: Panasonic NV-870 VHS Video Cassette Recorder (1985)

Given the age of the machine, it wouldn't hurt to blanket replace all power supply caps. Any sort of ripple emanating from there will cause all sorts of weird and (not so) wonderful symptoms.

Sometimes it's really easy to tell if there's capacitor issues as the VFD will come on really dim (from cold), and then slowly come up to full brightness. I like to think of the VFD as the window to the VCR's soul!
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Old 7th Apr 2018, 12:25 pm   #10
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Default Re: Panasonic NV-870 VHS Video Cassette Recorder (1985)

Thanks to everybody for the feedback on this. Some progress:

I managed to fool the unit into thinking that a cassette was inserted by using blutac to hold down the lock out pins at the top of the cassette tray, and by sticking some tape over the opto-sensor that goes into the cassette, when the cassette is loaded. This way I can load and eject the cassette tray in and out whilst watching the mechanism beneath the cassette in operation. The cassette tray seems to load fine now, with none of the sticking happening when a cassette is fitted. I think I can see the cause of a couple of the problems:

On the weak take up reel operation, it seems that pressing on the rubber idler slightly against the reel/spindle, means that more torque can be felt through the take up spindle. The arm for the idler moves over into position via a slip clutch by the look of it, seems that there is not enough torque being transmitted through the slip clutch as well. It seems to be running slightly better now after a few hours of operation.

On the supply back tension, it seems that there isn't any, because there is no friction material on the copper band that wraps around the supply reel. I've looked inside but can't find anything loose laying around. So I need a new one or need to repair the existing one somehow. All the belts look ok and seem to grip to the wheels properly.

Hopefully if its just the lack of back tension that is causing the poor tracking, I could be on to a winner. As for those caps, and the others in the power supply, I'll do all that once the machine is mechanically running properly.
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Old 7th Apr 2018, 1:00 pm   #11
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Default Re: Panasonic NV-870 VHS Video Cassette Recorder (1985)

Quote:
Originally Posted by monaro0162 View Post
The cassette tray seems to load fine now, with none of the sticking happening when a cassette is fitted.
The tray will seemingly work without a tape because there is less load. Until you replace that belt (an o ring will do), it won't work reliably.

Quote:
On the weak take up reel operation, it seems that pressing on the rubber idler slightly against the reel/spindle, means that more torque can be felt through the take up spindle. The arm for the idler moves over into position via a slip clutch by the look of it, seems that there is not enough torque being transmitted through the slip clutch as well.
These are all symptoms of a weak drive belt and an idler tyre that has lost its elasticity. The idler flips over depending on direction of rotation of the pulley (which should also be cleaned/resurfaced). Don't complicate things - just replace the parts and clean the contact areas.
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Old 7th Apr 2018, 1:43 pm   #12
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Default Re: Panasonic NV-870 VHS Video Cassette Recorder (1985)

Thanks Ben,

Quote:
Originally Posted by ben View Post
The tray will seemingly work without a tape because there is less load. Until you replace that belt (an o ring will do), it won't work reliably.
I think that the belt is ok because the motor itself locks up when the tray sticks. But I will certainly try fitting some new belts. Would you know can they be sourced as a kit or would I have to source them individually?

Paul
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Old 7th Apr 2018, 7:04 pm   #13
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Default Re: Panasonic NV-870 VHS Video Cassette Recorder (1985)

Belt kit:
http://www.donberg.ie/descript/1/11126.htm
Back-tension band:
http://www.donberg.ie/descript/2/21015-g.htm
The part number for the idler is VXP0521 and can be found in many sites.

Fivos
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Old 7th Apr 2018, 10:58 pm   #14
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Default Re: Panasonic NV-870 VHS Video Cassette Recorder (1985)

It looks like the belts are just a little slack, so you could try boiling them in hot water as I've seen someone on YouTube do this regularly with success.

Simply throw them in a jug of water and stick them in the microwave for ten minutes. Just make sure the water doesn't evaporate totally! For the idler, perhaps something like MG Chemicals 'Rubber Renue' could work.
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Old 8th Apr 2018, 2:37 pm   #15
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Default Re: Panasonic NV-870 VHS Video Cassette Recorder (1985)

12voltvids. I love his videos. He does excellent work restoring old machines.

Fivos
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Old 13th Apr 2018, 9:44 pm   #16
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Default Re: Panasonic NV-870 VHS Video Cassette Recorder (1985)

I've ordered a new pinch wheel and back tension band from donberg, they weren't able to source the belt kit at the moment. In the mean time I bodged a piece of sticky foam onto the copper band and gave it a go. Low and behold it works and the picture is almost perfect! (for VHS). So I loaded up my old MTV tapes, and it's 1990 again! These were recorded off the astra satellite and would have been in wegner stereo? The sound quality is very good. The machine still doesn't rewind properly donberg list the suspect clutch mechanism but at 40 euros I don't think I'll bother at the moment. I've attached some MTV VHS replay photos, and a photo of the setup with the umatic beneath. I also got a very nice JVC TM-H150CG crt monitor to run some picture quality comparisons.
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Old 13th Apr 2018, 9:45 pm   #17
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Default Re: Panasonic NV-870 VHS Video Cassette Recorder (1985)

further pics
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Old 13th Apr 2018, 10:49 pm   #18
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Default Re: Panasonic NV-870 VHS Video Cassette Recorder (1985)

Nice. When MTV was a real music channel...
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Old 14th Apr 2018, 8:48 am   #19
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Default Re: Panasonic NV-870 VHS Video Cassette Recorder (1985)

Quote:
The machine still doesn't rewind properly donberg list the suspect clutch mechanism but at 40 euros I don't think I'll bother at the moment.
I have had success removing the rubber tyre and refitting it inside out, a bit fiddly but works a treat!

Mark
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Old 16th Apr 2018, 4:33 pm   #20
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Default Re: Panasonic NV-870 VHS Video Cassette Recorder (1985)

If you share a photo I more than likely have a brand new Panasonic one you can have, gratis of course.
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