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Poor signal needs troubleshooting 101

Discussion in 'HDR-1800T/HDR-2000T Freeview Recorders' started by monusalv, Feb 15, 2015.

  1. monusalv

    monusalv New Member

    After that slight interruption from @Faust

    Just for clarification, I'm not "pointlessly trying to avoid an HDD reformat". On the contrary and as the thread title suggests, I'm trying to learn how to understand my symptoms and systematically diagnose where the problem lies. It's really not my intention to challenge the generous advice being offered, but I'm one of those slightly geeky types who kinda needs to know why he's doing something (and I admit, probably over-thinks it).

    As @prpr advocates, I could just replace all my coax with WF100, and it would certainly improve the system, but if my actual problem is elsewhere it's not going to solve it, nor help anyone with a similar problem.

    So my understanding at present is that
    • We're agreed that raw signal is within limits
    • The defects occur in both HD and SD transmissions.
    • There is no known pattern when they occur - every minute for 5 mins then nothing for 24 hrs, both during the day and in the evenings.
    • The defects happen while watching both live transmissions and recorded programs.
    • They are not necessarily repeatable on playback; that is, I can have a drop-out of sound while watching a live transmission or a recording; then when I skip back I can (but don't always) get the sound in full, or at least more of the sound than at first time through.
    • Symptoms only occur on HDMI cable, and disappear completely when using Scart or RCA video & audio connections.

    I'll happily do a factory reset with or without a HDD format if that is next on the troubleshooting list but my curiosity immediately asks questions like:
    • What is the reset designed to do which may eliminate these symptoms? It seems a bit counter-intuitive that HDD faults cause a problem watching a live transmission?
    • Why does the problem only occur through HDMI cable? If it's not a problem with the cable itself (I've tried 2) what processing route within the box is common to playback and live.
  2. Black Hole

    Black Hole Theloniuos Abbot

    That's worrying - are you sure? It's difficult to be sure that something infrequent doesn't happen at all.
  3. prpr

    prpr Well-Known Member

    Well you've got to start somewhere and try something, and that is (IMHO) the most obvious, least disruptive and lowest risk thing to try.
    I don't know what reset/format would achieve either. The most likely cause is interference between HDMI and aerial.
  4. Trev

    Trev The Dumb One

    Then your co-ax run must be the easiest in the world if replacing it is "least disruptive and lowest risk thing to try.". I would certainly only replace mine as the very last resort.

    The OP claims that he has adequate signal strength and it works OK with the HDMI cable disconnected. I do however agree that "The most likely cause is interference between HDMI and aerial" and using good quality double screened co-ax from the TV aerial outlet point to the Box/TV has some mileage in it to reduce the possibility of HDMI breakthrough onto the aerial cable in the vicinity of the 'back of the set spaghetti'
  5. Black Hole

    Black Hole Theloniuos Abbot

    Factory resets, or as a last resort HDD formats, have been known to resolve glitchy behaviour if the problem is internal. Disk write retries interrupt the processing, parameter corruption in the databases are flushed by a factory reset.
  6. monusalv

    monusalv New Member

    Removes egg from face.

    Sorry to throw this into the mix at such a late stage but just tonight I realised the elephant in the room which I hadn't mentioned is that my sound is processed through an inherited JVC receiver/amplifier. It's a model RX-5062S and although it's described as an "audio/video control receiver" in practice it only has audio connections. To be honest, I'd quite forgotten about it as the display is muted and it's linked to my TV remote so they both come on/off together. I run the JVC connected from the optical TV out on my Samsung TV so I don't have to mess with the JVC to change source when switching between TV and Hummy. When I switched to the 2000T this connection wasn't affected.

    What I've now observed is that the JVC is set to AutoSurround so it selects Dolby or DTS when a suitable signal is detected. Normally it works on DTS for all my TV and Hummy signals but peridically it's dropping out of DTS mode into something called "Dolby ProLogic II Movie" mode. Seems that's when the sound glitch occurs.

    So now I know the sound is dropping out due to the delayed response of the JVC switching modes, which is triggered by a change (degredation?) of digital signal encoding. Next question - Why?

    Posting this at bed-time, but I just thought the obvious thing to do is try the optical port from the hummy direct into the JVC. I'll get to it tomorrow and let you know.

    Oh, and so far as I know, my coax down wire is embedded in a cavity wall which has nowbeen injected with insulation.
    Last edited: Feb 20, 2015
  7. Black Hole

    Black Hole Theloniuos Abbot

    That's an oops!
  8. Trev

    Trev The Dumb One

    Then replacing the co-ax would definitely been ""least disruptive and lowest risk thing to try." then? ;=)
  9. NeilN

    NeilN Member

    This one is interesting. I've just had my 2000T exchanged under warranty. For the identical symptoms described in this thread. On all SD and HD channels I would experience momentary picture freezing, sometimes for up to a second on SD channels with the audio usually present. The same on HD channels but audio break would sometimes happen. On a couple of occasions I got the no signal message very briefly. Went through the factory reset, manual tune, and reformat and eventually re-flash of firmware with Humax support on the phone. I even sent them video clips of the TV screen so they could see the problem. All the other equipment on my aerial system is fine, including the two HDR FOX T2's I have. Humax arranged a courier replacement/collection service.
    The new 2000T was manually tuned. And after 48 hours I have exactly the same symptoms again with the replacement unit. :-(

    I have read this thread and others reporting similar symptoms on the 2000T. I have a feeling that this issue is actually a bug in the firmware. And this is the reason for my assumption.
    If I re-boot (full power down and HDD stop) the 2000T when the issue is present. Once rebooted the problem disappears for an as not yet fully determined period of time. This was also the case for the original unit I purchased that was exchanged for the one I have now. I noticed that over the 10+ times I had to reboot it. It would run perfectly for some where between 8 and 48 hours between re-occurance of the issue and having to re-boot to clear it.

    Signal strengths for reference were: SD - S/S 75% to 88% and Qual unwavering at 100%. HD - S/S 80% to 92% and Qual again an unwavering 100%.

    Now waiting a phone call from Humax support as I sent a video clip of the TV screen of the new box. Hoping to arrange a refund. And I'll go buy a third T2 (second hand). I think that's the best solution to this problem for the time being. Maybe if Humax sort the 2000T turd out. I might consider purchasing one again.

    Finally, here's a good one. When talking to the guy at Humax on the phone I discussed the differences between the T2 and 2000T stating that the T2 was by a long way a far better machine than the 2000T.
    His response was. 'That is the general consensus in the office here as well'. Sound's like the 2000T is a bit of a thorn in their side and they are dealing with many unhappy owners daily. Wonder how many Hummy employees have T2's with CF installed? :)

    I'll be happier when I UPGRADE to another T2 as it's replacement. :)

    If anyone is having this issue with their 2000T. Try re-booting the bugger to see if that clears it.
  10. MartinLiddle

    MartinLiddle Super Moderator Staff Member

    Have you considered the possibility that the signal strength is too high? Our HDR-2000T started to display picture bad break up on a very low signal strength. On investigation I found a badly made connection in the cabling to the professionally installed distribution amplifier. Having fixed this the signal strength was over 90% and there was still significant picture break up. Reducing the gain on the distribution amplifier helped a bit but signal strength was still around 90% when on minimum gain. Fitting a variable attenuator to the aerial feed to the box and getting the signal strength down to 80% improved things further but it is not completely perfect but I haven't had time to investigate further.
  11. Black Hole

    Black Hole Theloniuos Abbot

    But the quality registering "unwavering at 100%" seems to discount that possibility.

    Software faults which manifest after a period of operation can often be pinpointed on "memory leaks" - use of a system resource which is not properly managed so that the resource runs out (eg a stack when there are routinely more pushes than pops).
  12. NeilN

    NeilN Member

    Its not that. If I put the 2000T after my two T2's in the aerial chain the overall level drops by about 6%. And it still does it.
    OK then if it's a signal level problem why does it disappear after rebooting the box?
    Oh I had signal level/quality from my Aerial system tested by an installer last year and it is spot on where it needs to be for DVB-T/T2 recievers.
  13. NeilN

    NeilN Member

    Agreed. This does have that ring to it. Resetting the system puts it all back in order for a while.