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Old 2nd Aug 2021, 4:30 pm   #1
andrewferguson
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Default Strange issues with Panasonic NV-HS830

I've had this VCR for just over a week, after getting it off ebay. Unfortunately, I'm already running into issues.

It all started when I plugged a SCART -> S-Video / composite adaptor into the VCR. I'm pretty sure that's just a co-incidence, but I will be going over the adaptor with a multimeter later to see if something is amiss. When I plugged the adaptor in, the tape that was playing fine suddenly started going on high-speed fast-forward (plugging in the adaptor while a tape was playing was pretty stupid, I'll admit). The buttons on the front panel didn't respond to me franticly trying to stop the tape, so I pulled the plug from the wall.

When I plugged it in again, I observed the following issues:
  1. There was no video or audio being outputted.
  2. The 'seconds' counter on the front display was increasing too quickly.
  3. The front panel buttons didn't respond beyond making the button's symbol appear on the display (ie: pushing the 'fast-forward' button would make a fast-forward symbol appear on the front-panel display, but the tape would continue moving at the same speed and there was no other change).
  4. The only way I could eject a tape was by powering the machine on and repeatedly pressing the eject over and over. After two or three tries of this I could get the tape to eject.

I thought that was going to be the end of things, but I wanted to double-check to see if there was any audio coming out of the RCA jacks (I was connecting it to the TV over SCART). I carried it into the room with my HiFi, and connected up the RCA audio, and low-and-behold, it started working. (Or, at least, the audio was playing and all the front-panel buttons are working as expected - I can't check the video as there's no TV in this room).

I then carried it back into the room with the TV, and much to my annoyance it had stopped working again. Not the same issues as before, something much more simple: every time I put in a tape, it would immediately eject it.

As a last resort, I carried it back to the room with the HiFi, and the blasted thing is working again! Right now I have it running in that room, playing the audio through my HiFi. My plan is to play the tape through till the end, in case that resets something.

This VCR is made in 2002 I believe, so is probably stretching the definition of "vintage", but I think there are several folks on this forum who have good knowledge of servicing VCRs and might be able to help, or who may be familiar with the symptoms I have described?

This seems to be a rather 'cursed' VCR...
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Old 2nd Aug 2021, 6:10 pm   #2
G6Tanuki
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Default Re: Strange issues with Panasonic NV-HS830

There can be ab issue with some combinations of devices where the suppression-capacitors - which form an AC centre-tap across the mains, with the centre-tap connected to the [un-earthed] chassis - inject noise-voltages - which can be significant - into the interconnections.

If the interconnections are hot-swapped [or swapped when the equipment is powered-up] it's possible for a significant spike to be fired into the active pins of the interconnects - the big issue here being that on the usual red/white/yellow RCA phono-plugs the centre contact mates before the screen - so any voltage-differences between the two devices get applied to the active components first when plugging/unplugging the interconnects.

The spikes can cause associated control-circuits/microprocessors to enter undesirable states - and/or permanent damage!

[I've known a rather-expensive DSLR camera be damaged because of this, when the owner connected it to his laptop and both of them were on-charge from their associated power-bricks].
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Old 2nd Aug 2021, 6:31 pm   #3
Welsh Anorak
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Default Re: Strange issues with Panasonic NV-HS830

Yes, hot-plugging has rendered many a TV's main board beyond repair, though usually this is due to th HDMI inputs.
However the first thing I'd do is to clean or replace the mode switch. This can confuse the mechanism control and cause it to do odd things. Also it's getting on for twenty years old, so power supply capacitors will be showing their age by now.
It doesn't sound like any lasting damage has been done, and it could all be co-incidence.
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Old 3rd Aug 2021, 7:35 am   #4
toshiba tony
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Default Re: Strange issues with Panasonic NV-HS830

Hot plugging, yes, it had never happened to me but I damaged the hdmi input on a tv once. Now I always advise customers not to do it, scare mongering perhaps but better safe than sorry.
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Old 3rd Aug 2021, 3:02 pm   #5
andrewferguson
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Default Re: Strange issues with Panasonic NV-HS830

Thanks all for the responses.

It definitely isn't back to fully working yet - I tried again a few times yesterday connected to a TV, and it worked around half the time. The other times it was back to the original issue (playing tape at too fast a speed with no video signal, and the front-panel controls do nothing). One thing I forgot to mention was that when it gets into this "mode", I can push the front-panel power button and the 00:00 (unset clock time) starts blinking on the front display. But the tape continues to move at the faster speed.

I tried it again today and it seemed to work OK, but I definitely think it's going to continue to be temperamental.

I honestly thought that hot-plugging SCART would be OK, since it has the surrounding shield that connects first. It turns out I was very wrong:

Quote:
Due to the relatively high signal voltages used in SCART, "hot plugging" (connecting or disconnecting devices while they are on) is not recommended. Although there is no risk of personal injury, there is the possibility of damaging electronics within the devices if the connector is inserted improperly.
(From wikipedia). The article goes on to warn that on some Class-II TVs, connecting the TV-end first could result in the shield becoming live at around half mains voltage - also something I was not aware of.

This has definitely been a lesson in the dangers of hot-plugging for me, although I still suspect that it could just be a coincidence that it started acting up at the same times as I used the SCART adaptor. On that basis, I will visually check the power supply capacitors for obvious signs of damage / leaking, and try and figure out where the mode switch is so I can inspect / clean it (thanks, Welsh Anorak, for informing me about the existence of this component!).
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Old 3rd Aug 2021, 5:36 pm   #6
Nickthedentist
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Default Re: Strange issues with Panasonic NV-HS830

Could it be something as simple as a hairline crack on the PCB, which was disturbed by pushing a plug into a board-Mounted socket?
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Old 4th Aug 2021, 3:54 am   #7
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Default Re: Strange issues with Panasonic NV-HS830

Hi.
I would look for dry joints on the end sensors and the led that sits below the prism.
Then clean the mode switch on the board below the mechanism.
The fact that commands appear on the display means that the micro is working but the loading motor is not being driven.

It looks to have the Z mechanism.
I tried to attach the manual for the deck, but it is a little too large.

Best of luck.

Wayne.
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Old 5th Aug 2021, 9:41 am   #8
G6ONEDave
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Default Re: Strange issues with Panasonic NV-HS830

Might be worth checking the 12v supplies in the psu. One of them could have suffered via the 12v sense pin in the scart connector system getting zapped with the spark.

Dave
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Old 5th Aug 2021, 8:35 pm   #9
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Default Re: Strange issues with Panasonic NV-HS830

Do these use one of those STK regulators in the PSU? They can throw-up some weird 'n' wonderful faults when they go faulty. Perhaps there is a low, missing, or noisy output rail that is confusing the micro?
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