National NV-8600 problems

[dj_fivos_sak]

So I just got this vintage Panasonic VCR manufactured in November of 1979! And yes, it is the rare multi system version with PAL, SECAM and NTSC! I managed to get play, FF and REW to work but it now has three problems.
1. The tape does not get back into the cassette when unloading.
2. The back-tension band is deteriorated and has fallen off.
3. It doesn't record audio.
Has anyone ever worked on these older Panasonic units to give me an idea of what's wrong?

[birksholt]

I have got the very similar NV8610, I've not got it in front of me at the minute but I will have a look at it and at the service manual and see what i can tell you. Mine is not fully working as it needs a new pinch roller which, from what i can tell, you can't replace on its own (it is the entire assembly with the metal arm). I can probably scan you the relevant parts of the s/m if needed. It is actually the one for the 8600 so would be accurate. I seem to remember I had similar problems with tape being left out. Have you checked all the idler tyres? Those Panasonics are a bit more difficult to work on than the Fergusons of the same time, more fiddly.

[dj_fivos_sak]

I have cleaned all the idlers and replaced a couple of belts. On mine, the pinch roller just lifts out by removing the cap on top of it. Can you scan the manual please?

[birksholt]

The cap doesn't seem to come off on mine, it seems to be stuck on. I will have another look at it though and see if it does. Is it screwed on under the cap?
I will try and scan it tomorrow but it might end up being at the weekend. Have you tried covering the sensors etc and getting it to lace up and unload to see what is happening during the unloading? You might be able to see if something is slipping.
As for the back tension band, is it that the felt strip has separated from the metal? If the felt strip is still there but detatched, you may be able to glue it back on. If not, I'm not sure where you would get a new one.
For the audio recording, you will most likely need to trace the signal so I will include that bit in the scan.

[dj_fivos_sak]

Here's how to remove the pinch roller. You just lift the white cap straight out. Yours might be gummed up. As for the tension band, as you said, the felt strip is seperated. I tried glueing it back but it failed again.

[birksholt]

Yes I tried that but it won't come off. It seems to be glued in or something. Also in the service manual, there is no separate part number for the arm and the roller, there is just a number for the 'pressure roller assembly'. It has been a while since I tried it though so I'll get it out and have another go at it, hopefully it will come off. I think it will probably be tomorrow or Sunday when I will get chance to scan the service manual.

With the back tension band, I have managed to glue it back on with superglue on a couple of occasions (one was on a camcorder, what a faff that was), but I suppose if it's too far gone you'll have to try and get hold of another one either new or from a scrap machine. Maybe you could get some felt from somewhere and cut a piece to size, I've never tried this though so I don't know how well it would work.

I don't know how picky this machine is about the back tension, I know with the Fergy top loaders as long as it's vaguely correct it will work. When I got mine, I don't know if the band had shrunk somehow but it was mega tight. It didn't look fiddled with though, the paint was still on. I ended up loosening it off as the reel wouldn't even turn.

[ukcol]

I hope I will be permitted to go slightly off the main topic of this thread.

I remember the Panasonic NV8600UB from 1979 which was the PAL only model sold here in the UK. Like all the machines of the time they were over engineered but more so. The later NV8610UB had different heads and electronics to allow for a noise free paused picture. Like all new technology before it was fully understood this noise free pause seemed like magic to me.

[dj_fivos_sak]

Thanks for the info ukcol! I actually didn't know the difference between the 8600 and the 8610. When I press pause, the picture goes blank. There's also the 8620 but I don't know much about that.

[ukcol]

That is interesting, I didn't remember the NV8600UB blanking the picture in pause but nearly 40 years have passed since the company I worked for was selling them.

[dj_fivos_sak]

Did you mean NV-8600B? The UB suffix was used in Sony Betamax units for the UK market. See this video of the NTSC version of this VCR: https://www.youtube.com/watch?v=vSBPBjCd8u0

You can see what happens when he presses pause.

[ukcol]

Originally Posted by dj_fivos_sak

Did you mean NV-8600B?

Yes NV-8600B.

You are right UB was used to indicate UK models of Sony products, not just videos of course.

[birksholt]

Managed to get the cap off the pinch roller. Pried it off with a screwdriver. I think it had got seized over the years. Thanks for the advice on that.
Winding the tape in on unloading is done by the rewind idler which should move across as shown. Is it moving across and spinning? I am not sure off the top of my head if the small belt attached to it is what runs it or if that runs something else. I suspect the latter as on mine it is in pretty bad condition but the unloading is fine. Its strange that rewind works but its not pulling the tape back in when it unloads.

[dj_fivos_sak]

I found the problem. When I hit stop, the rewind idler engages with the supply reel table but the capstan motor stops spinning. It should continue spinning until the tape is unthreaded. So I actually have an electronic issue, not mechanical! Can you scan some pages of the service manual please? I need the schematic of the motor drive circuit and the audio circuit. Also, what is the part number of the head drum (VEHxxxx)?

[birksholt]

Yes. I'm out at the minute but I'll scan it when I get in tonight. I think the head drum is VEH0121 but again, I'll check when I get in.

[dj_fivos_sak]

Thanks! My NV-7500 actually has a VEH-0121 drum!

[birksholt]

My mistake, it's actually VEH0115. Here are the scans from the service manual. Let me know if you need any more.

[ben]

Originally Posted by birksholt

With the back tension band, I have managed to glue it back on with superglue on a couple of occasions (one was on a camcorder, what a faff that was), but I suppose if it's too far gone you'll have to try and get hold of another one.

My tip for this common problem is basically: do not use superglue! It's too thin/liquid, and ends up being absorbed by the felt. You need a thicker glue.I think the last time, I used something similar to UHU which was sold as ideal for glueing leather etc!

[birksholt]

you're right it did get absorbed a bit. I just put a dab at each end and one in the middle and that was just enough to keep it in place without it getting soaked in glue and drying hard. Yes superglue not ideal. Thanks for the tip I think I will get some of that for future use.

[dj_fivos_sak]

Too late. I used super glue. Now it won't glue back in and it is hard.

[birksholt]

That australian site you pointed me to has the tension band for this
http://www.telespares.com.au/index.p...ucts_id=322718