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Old 20th Jul 2019, 6:50 pm   #1
monaro0162
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Default Panasonic NV-F65B - and bonus hedge find VCR's

A while back I picked up a Panasonic NV-870 at a boot sale for a £1. I bought it as I was interested in the HiFi Stereo soundtrack implementation, that offered quality almost as good as CD. I had an NV-830 that I bought in 1984, one of the first VCR's offered with the HiFi soundtrack, I remember the sound quality being very good. So the 870 would be great for my collection of analogue tape recorders. Unfortunately, I've never managed to get it to work properly (what do you expect for £1!) so on Tuesday I bought a very nice looking NV-F65 HQ on ebay, and waited for it to arrive a few days later.

I cycle to work my route mostly takes me through forest paths, woods and farmland. On Tuesday evening I had to go into town before going home so I took a different route to the usual one. After I'd finished in town, I headed home on a bit of a made up route that took me through some forest, as I'm going along a track not far from a lay by, I spotted a box with some wires hanging out of it near a hedge. So I stopped to take a look to see what was inside and what did I find? Not one, but two vcrs and one remote control in the box! The plugs had been cut off the VCR's, and they were a bit dirty and damp, there is a recycling place nearby, may be someone was taking them there but found that it was shut so they just chucked them over the hedge in the lay by?

So I picked up the smaller of the two units, and just about managed to stuff it in my back pack before heading home.

The next morning my curiosity got the better of me and I diverted from my usual route to go and see if the second VCR was still there. It was, and as I had my bigger back pack with me, I managed to get it in and off to work I went. As i was on a different route, I managed to get a bit lost in the woods before working out where I was and carrying on. That evening I did the full trip home with the second VCR on my back, lucky it wasn't too heavy!

A remote control for the LG from ebay arrived this morning, so I spent some time taking a look at the finds: A Digilogic VCRDVD2 combo unit with remote, and a LG LV880. May be they'll work, may be they won't. So after some cleaning I found that the LG works perfectly, and the VCR was working on the Digilogic, but the tray wouldn't open on the DVD part. A new belt soon fixed that. Both machines work fine and the picture quality is really good.

What are the chances of that happening? Did the purchase of the NV-F65 trigger a random bonus VCR find? "Lost in a forest on a bicycle with a VCR strapped to your back"

Anyway the NV-F65 arrived today, complete with all the manuals, remote control and original packaging, in lovely condition. However it does have one issue: (May be that's irony) Sometimes it won't power up, even in standby, the display is completely blank. When it does power up, it works perfectly. It seems to be related to something physical, when you move the unit it looses power completely. It's not the power connector at the rear, as if you wiggle this when the unit is operating normally, it doesn't loose power. Yet of you move the main body, sometimes it will loose power.

I've had it running fine for the last few hours, without moving it at all, to give the electronics/caps a chance to recover if the unit has been dormant for a while. Anybody know what the problem could be? I've re-seated the fuse in the power supply a few times, made no difference. Power supply fault, or logic control fault? I've noticed that when the unit does power up successfully, a faint click can be heard from (maybe) behind the display?
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Old 20th Jul 2019, 7:46 pm   #2
Freya
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Default Re: Panasonic NV-F65B - and bonus hedge find VCR's

I would look for dry joints on the front display board anywhere around the microprocessor.
Nice find on the other two, keeps the countryside clean as well.
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Old 21st Jul 2019, 12:31 am   #3
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Default Re: Panasonic NV-F65B - and bonus hedge find VCR's

About two years ago I pulled a Grundig TK5 tape recorder out of a wast paper basket at the end of my street.
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Old 21st Jul 2019, 6:39 am   #4
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Default Re: Panasonic NV-F65B - and bonus hedge find VCR's

Surely the NVF65 is the usual 1uF 400V in the psu...
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Old 21st Jul 2019, 10:35 am   #5
monaro0162
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Default Re: Panasonic NV-F65B - and bonus hedge find VCR's

I made some audio test recordings on it last night. The recording quality is excellent and way better than any cassette machine that I have. The HiFi stereo system still works at half speed (LP mode) which will give an 8 hour recording time with a E240 tape. I did some research on how the system works and was surprised to find out that it actually overlays the audio signal over the video signal at a different depth on the tape ... I wouldn't have thought that this was even possible, clever stuff.

I left it running overnight recording Radio6 and have been playing it back this morning. All fine, until I gently tried putting the top cover back on .... total loss of power again. Some gentle tapping and careful flexing around the pcb and various other places within the recorder has made no difference. Resetting the mains at the mains plug, no difference. Refitting the figure of 8 mains plug in and out of the power supply, no difference. I can hear a slight bit of interference through my hifi when the plug is inserted and removed, so it looks like the power supply might be drawing some current. So now I will leave it completely powered down for a while and try again later.

Quote:
Originally Posted by dsergeant View Post
Surely the NVF65 is the usual 1uF 400V in the psu...
Could this capacitor cause the symptoms seen?
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Old 22nd Jul 2019, 12:49 am   #6
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Default Re: Panasonic NV-F65B - and bonus hedge find VCR's

Unlikely, the 1uF capacitor is for starting it from cold.
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Old 22nd Jul 2019, 12:34 pm   #7
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Default Re: Panasonic NV-F65B - and bonus hedge find VCR's

All electrolytic capacitors are suspect (should really be replaced), but they won't usually cause intermittents. Unless, maybe, leaked electrolyte caused traces to break.
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Old 22nd Jul 2019, 12:57 pm   #8
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Default Re: Panasonic NV-F65B - and bonus hedge find VCR's

The 1uf cap mentioned would normally cause a dead set, certainly change all other Secondary caps as well for reliability.
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Old 22nd Jul 2019, 2:50 pm   #9
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Default Re: Panasonic NV-F65B - and bonus hedge find VCR's

The capacitor that causes SMPSUs not to come back on again after being switched off is the one which smooths the power to the control chip. It's normally fed from the tertiary winding on the transformer, via a fast rectifier diode; and it's located in the "danger zone" since it is connected directly to rectified mains.

When the oscillator is not running, there is no way to get any charge into this capacitor, leading to a "Del Boy's Briefcases" situation. So to start up the oscillator, there is also a large resistor (often two resistors in series, for voltage rating purposes) from the +300-odd volts DC line to the positive terminal of the capacitor. This allows the capacitor to charge slowly and eventually start up the oscillator, after which there will be a supply from the tertiary winding; but if the capacitor goes electrically leaky, then the voltage may never build up enough to start the oscillator.

The startup resistor has to have a large value, as it stays in circuit dissipating power uselessly once the oscillator is running.
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Old 22nd Jul 2019, 8:42 pm   #10
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Default Re: Panasonic NV-F65B - and bonus hedge find VCR's

Thanks to everyone for the advice on this.
I kind of suspected that it wasn't the 1uF at the 'front' of the cct.
I did an internet search and found a post on here from "John123" in 2011 that lists known problems with the 65B and at the top of the list I found ...

"Just for reference, below are some common faults for the NV-F65/ 65B:

Appears dead for first 3-4 minutes after switching on:
IC7503 MN1280L reset IC on timer PCB"

Which could cover the problem with my machine

I've now placed it on a shelf with the cover on and I'm not moving it, and it seems to be behaving itself. Lovely machine, the picture and sound quality are excellent.

Cricklewood electronics list an MN1280L so I'll order one. Anybody know how easy it would be to replace? I don't have a service manual, I've been unable to locate one so far.
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Old 22nd Jul 2019, 10:56 pm   #11
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Default Re: Panasonic NV-F65B - and bonus hedge find VCR's

The MN1280L appears to be a three legged device, so no more difficult than replacing a transistor I guess...

Full service manual: http://freeservicemanuals.info/en/se...asonic/NV-F65/ 72.2Mb PDF file, 100 pages.

N.B. I don't *think* I'm breaking any rules giving a link to the manual...
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Old 22nd Jul 2019, 11:43 pm   #12
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Default Re: Panasonic NV-F65B - and bonus hedge find VCR's

I'm not sure there's a reason to suspect this device in particular, other than that it could cause vaguely similar symptoms. I'd first rule out the power supply before going into processor territory.
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Old 23rd Jul 2019, 1:35 am   #13
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Default Re: Panasonic NV-F65B - and bonus hedge find VCR's

Look for dry joints or cracks on PCBs in the power sections.

It's also worth wiggling the mains lead as there could be a break in it. Is the mains plug a rewireable type if so have you checked the security of the terminal screws and fuseholder?
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Old 23rd Jul 2019, 8:32 pm   #14
monaro0162
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Default Re: Panasonic NV-F65B - and bonus hedge find VCR's

Just to clarify the symptoms: Intermittently, if you move or tap the chassis, it looses power completely. I've checked the continuity of the mains cable and its fine. When the unit has powered up correctly, it stays so when the mains 8 plug is wiggled about in the socket, as long as you don't move or tap the chassis. If it looses power, no amount of mains resetting, cable wiggling, or chassis tapping will make it work again. Leave it for between 15 and 30 minutes .... then it will power up again....which led me to think that it could be something to do with the MN1280L.

Now that I have the manual (thanks for the link!) I'll take a closer look at the psu and the wiring ... and also identify where the MN1280L is fitted.
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Old 23rd Jul 2019, 9:48 pm   #15
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Default Re: Panasonic NV-F65B - and bonus hedge find VCR's

Must be drys.
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Old 23rd Jul 2019, 11:25 pm   #16
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Default Re: Panasonic NV-F65B - and bonus hedge find VCR's

Quote:
Originally Posted by monaro0162 View Post
I did an internet search and found a post on here from "John123" in 2011 that lists known problems with the 65B and at the top of the list I found ...

"Just for reference, below are some common faults for the NV-F65/ 65B:

Appears dead for first 3-4 minutes after switching on:
IC7503 MN1280L reset IC on timer PCB"
Must be over eight years ago, now. How time flies! Anyway, I second the earlier comments that it's most likely to be dry joints in this scenario. Whenever there's something to do with physical movement like this, you can pretty much bet on it.

It could still be linked to the IC, as if a reference voltage is missing it will do its thing..but all that means is that it's probably doing its job!

Also, thanks to Julie for the explanation of the start-up cap. It does seem to be quite a common fault with this line of machines (especially the more upmarket S-VHS ones), as they all share very similar power supplies.
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Old 24th Jul 2019, 6:00 pm   #17
monaro0162
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Default Re: Panasonic NV-F65B - and bonus hedge find VCR's

Thank you John and Hamish, I agree it does look like it could be drys, the MN1280L ... or a combination of both! I will investigate further next week.
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Old 24th Jul 2019, 6:04 pm   #18
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Default Re: Panasonic NV-F65B - and bonus hedge find VCR's

Dry joints were unusual on Panasonics, but if one occurred it was most likely on a plug/socket connector. I'd trawl around the various interconnections, unplugging and re-inserting each, checking the ribbon cables and inspecting the soldering of the sockets with a magnifier.
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