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Opinions on DVHS problem? (rolling bars)

Discussion in 'Televisions' started by Geoff_D, Aug 2, 2005.

  1. Geoff_D

    Geoff_D
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    This is a long shot, seeing as DVHS is dead as a dodo, but do any resident DVHS enthusiasts have any idea what would be causing rolling bars on playback? The deck is a JVC 40K (factory refurb) and the display is a Sony KE32TS2, hooked up using an IXOS component cable.

    I'm getting very thin rolling bars over the 1080i picture that grow in intensity until the image looks like I'm viewing it through Venetian blinds. If I switch the output of the JVC deck to 480i, the bars go, but when I switch back to 1080i they're still there.

    I've tried different component leads with the same result, and I've been told it's not a ground loop problem (all bits of kit are connected to the same 6-way mains adaptor), so what could it be? I've done a search on the net and given the myriad problems that the JVC decks have had (I'm on my second :suicide: ) I thought I could find something like this - but no joy.

    I recently had some issues with static lines across the screen when viewing 480p though the component input of the set, but bizarrely they seemed to clear up. Could this be another symptom of a problem with the set's component input and nothing to do with the JVC deck? But I can't check this easily because A: I don't have another 1080i source to check the TV and B: I don't have another 1080i-capable display to check the JVC deck. :(

    Anyone?
     
  2. Bernard Barnett

    Bernard Barnett
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    Sounds to me like dirty heads. Have you got a head cleaning tape (the player should have come with one) and tried running it through?
     
  3. Stephen Neal

    Stephen Neal
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    I'm not sure about that - do you have a D-VHS machine ?

    As I understand it D-VHS suffers from freezing and digital blockiness when it has dirty/clogged head issues - as it is a digital, rather than analogue, recording format.

    Moving lines sounds like an analogue problem - so is probably part of the analogue output stages of the VCR or the analogue input stages of the display.

    If the OP bought either item from a dealer - they should be able to take the D-VHS machine into them and play it on a different 1080i capable display to see if the VCR is the problem?
     
  4. Bernard Barnett

    Bernard Barnett
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    Dear oh dear - would I have replied if I didn't have a player? My understanding is that dirty heads can cause all kinds of problems. Using a cleaner would be a quick and easy way of eliminating one possible cause. I bet it will be the first question asked if/when the machine goes to a repairer!
     
  5. pjskel

    pjskel
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    Now now boys, play nice!
    Geoff, given what you've said about the outputs giving different results, I tend to agree with Stephen's suggestion of taing it to a local dealer and trying with a Sony (same as your own) and another TV or two - JVC and Sharp, just to see if there is any consistancy between the problem and the other TVs.
    That way you should be able to narrow down where the issue lies. As it's a factory refurb, you'd like to believe it has been well tested before being boxed up again, but it could be indicitive of something that's been missed/overlooked, or a new problem altogether.
     
  6. Stephen Neal

    Stephen Neal
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    Sorry if my post caused any offence - but I know a lot of people assume "clean the heads" is an answer to any VCR issue - and thin lines of noise is a particularly analogue "head clog" issue... (Unlikely to be relevant to the D-VHS format)

    As D-VHS is based around digital recording of an MPEG2 transport stream (can't remember if it is shuffled to improve burst noise issues caused by drop out as broadcast D-VTRs are or not) - thin lines are not an artefact that can usually be introduced in the MPEG2 data domain (as it is a macro block-based encoding format faults are almost always block based at the minimum).

    Thin lines - which are described as similar to earth loop hum - are unlikely to be caused in the MPEG2 domain - and thus a function of the on-tape recording or replay (which would exhibit more block-based errors or freezing, or a strange reduction in frame rate with a wiping down effect) It is more likely they happen in the spatial domain - either analogue or digital so anywhere between the MPEG2 decoder and frame-store, through to the analogue output of the VCR, all the way through to the HD input and processing in the display.

    If the fault had been described as blocking, freezing, reduction in frame rate etc. - I'd agree with your advice to clean the heads. (Though excessive head cleaning is not good for heads - and so I'd never advocate it as a "cure all" first thing to try for any fault - though I know some dealers do to save time as it does cure a lot of playback issues)
     
  7. Bernard Barnett

    Bernard Barnett
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    Thanks for your polite reply and certainly no offence taken. I had the identical set-up to Geoff's until the whole lot was stolen. I've replaced the DVHS player with the same model but opted for a Pioneer display. It might be difficult for Geoff to test the player against another Sony as I believe that model has been discontinued. Totally agree that head-cleaning should be done sparingly but still maintain that it wouldn't hurt to try it once!
     
  8. Stephen Neal

    Stephen Neal
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    Yep - though I suspect if the problem was with the D-VHS output the fault would probably be visible on other 1080i displays - rather than being a specific Sony incompatibility.
     
  9. Geoff_D

    Geoff_D
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    Thanks for your replies guys. And yes, I've got head cleaners and have used them regularly on this deck to ward off the typical blocking/freezing problems. I've been pretty fortunate in that respect - then this **** starts happening. It seems to come and go, with the picture appearing fine for a length of time (which is quite variable) and then the rolling bars start.

    Sigh. I guess I'll just have to lug the deck to work and have a look with some other displays, but as the deck's tape transport mechanism isn't exactly the greatest I'll have to be extra careful. At least the DVHS deck can be replaced (didn't get it from a UK dealer so servicing is a dead end) - I just hope it's not the TV gradually going belly up because it's a very flexible set that can give excellent picture quality, from my laserdiscs right up to High Def.
     
  10. Bernard Barnett

    Bernard Barnett
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    If the problem does prove to be the player rather than the TV it might be worth giving CRT Projectors a call to consult them on a fix/repair. They import the machines (it was where I bought mine from - twice!) and they're a highly knowledgeable, top quality and helpful outfit. Don't know where you're located but they're in Norfolk. 01263 740096. Good luck!
     
  11. Geoff_D

    Geoff_D
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    I contacted CRT before I posted here! Henry is always very helpful, and gave me some good advice, although a service is pretty much out of the question seeing as I didn't buy it from them (and JVC UK wouldn't touch it with a bargepole).
     
  12. Nic Rhodes

    Nic Rhodes
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    Clean heads often helps here and there are dedicated DVHS cleaners, whether that helps... I think it does a little, the other thing I have noticed is it is worth having the 40k upto temp before playing (30 mins) and avoid hot temperatures....
     
  13. Geoff_D

    Geoff_D
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    Gah. I've just realised that it's the component input of my TV playing up again! Before, I got static bars (not rolling ones) on progressive scan (480p/576p) material from DVD but it strangely cleared up.

    The DVHS problem (thru 1080i) now does the same thing, except the rolling bars turn into the static ones (exactly like I see on progressive stuff) after a while and leave me with bloody great lines striking right across the screen.

    The odd thing is it only happened through progressive before. I was told it sounded like panel failure, but if so it would happen on all sources and not just prog scan thru component. If I switched the DVD player into interlaced 480i/576i the lines would go. I was all set to get an engineer out, then the problem vanished. Now it's back, and it's affecting my 1080i feed too.

    Getting it looked at is not a problem, but this issue has disappeared before and I'll bet money that it'll go again before I get the set picked up. Grrr....

    EDIT:Here's a pic. It's pretty big, but shrink to a reasonable size and you should be able to make out the lines going across the screen (it's playing a 75% magenta test pattern from DVE at 576p). The effect is much more apparent in person.

    http://web.onetel.com/~monkeyman/000_0143.JPG
     
  14. Bernard Barnett

    Bernard Barnett
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    Couldn't be the cable, could it? Worth trying a different one? Incidentally on DVD my understanding (others will correct me if wrong) that it's pointless feeding progressive to an ALiS screen - which is what your Sony is - as the display will re-interlace it. Obviously this point is not relevant to DVHS as that's interlaced anyway.
     
  15. Stephen Neal

    Stephen Neal
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    Not sure about the Alis point.

    AIUI Plasmas run at much higher refresh rates than 50Hz or 60Hz (as they use sub-fields to partially generate their grey scale). If the Alis interlacing is at the sub-field rate rather than the source field-rate then there may well be improvements from feeding it progressive - especially with 60Hz 3:2 pull down material where you get rid of the video frames consisting of two fields from different film frames (which doesn't happen with 50Hz 2:2)
     
  16. Geoff_D

    Geoff_D
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    To answer your first point, I've tried three different cables. Incidentally I run the component feeds from my progressive DVD and DVHS deck through my amp (only one component input on the plasma) and thought there might have been a conflict there. But I get the same effect when the signal is plumbed directly into the TV.

    And, as I predicted above, the image problems have now cleared up! I was all set to call the engineer, but then it reverted back to normal last night. I guess I'll just wait this infuriatingly intermittent fault out until it gets too chronic to live with...

    For all the guff about ALiS being 'interlaced' blah blah blah, I can simply state that progressive sources look ten times better than interlaced ones. Colours are more vivid, detail is significantly increased and I can confirm that NTSC sources look far more natural in terms of movement. I remember the first time I ran progressive through this set - the images were so sharp and crisp it was as if a veil had been lifted from my favourite movies.
     
  17. Quickbeam

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    As I understand it, an ALiS panel displays 1080i as 1024i interlaced, with slight vertical cropping. However, all other signals are displayed as 512p progressive. So ALiS panels can run in both progressive and interlaced modes, albeit using the same number of lines.
     

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