Hi all

I've been a keen fan of this machine since I got it a few years ago although now is giving me some problems, wondered if you could help?

I live in W Sussex and have never been able to d/l the latest firmware (wrong MUX I believe) despite following the advice on this forum religiously when it came out. Have been using the machine with the old firmware (1.something) without too many problems since purchase.

However recently the reception on the unit has become appalling (stuttery pics and audio) and have had my aerial guy back in to check it out. He reported no problem with the new aerial he fitted and isolated the issue to the DHD4000, as reception directly to the TV was fine (in fact more channels picked up this way!)

I'm no electronics engineer but wondering if any of you had any tips on how to get under the bonnet to get this sorted? Only other option it seems is Sky+ but don't want to give Murdoch the satisfaction!

Thanks

I had stuttery playback a couple of times, but pulling the mains plug out for a few minutes cured that.

Have you kept your channel list up to date, by rescanning?

Tip: do not try scanning for channels when listening to radio stations; I did that recently and got sound, but no pics on the tv channels! Instead, get both tuners locked onto BBC1 and BBC2, simply by changing channels, then go into the menu and scan for channels.

Have you got sufficient space left on the disk? No corrupt recordings? (Try watching and deleting your programmes one by one).

When you have watched all recordings, you might try a 'format disk' which is hidden in the 'Engineering Menu'. This will erase the disk and the 14 day EPG. This may be necessary, as there are no defragmentation procedures for pvrs, and there is a chance that the files have been spread about all over the disk, slowing down access times.
(Menu - 6 - 9 (to get to the 'Technical Menu'). Dial '1004' to access the 'Engineering Menu'); after a second or two, a small menu will appear.

The 'format disk' function is somewhere in there (can't remember which at the moment!). It should only take a few seconds. It seems to only erase the master index file on the disk, but the recordings will have lost their 'logical paths', if you will, so they will be unwatchable.

The EPG will only allow 'Now & Next' programme information until the next 3.00am download.

Given the specialised nature of the filesystem, I don't believe fragmentation would ever become serious enough to impact performance, necessitating a reformat of the drive.

The fact that you say you are receiving more channels on the TV than on the PVR does suggest a signal problem. Perhaps either the incoming signal strength has dropped (but the TV's tuner is more sensitive) or the Thomson's tuners have gone a bit deaf.

I'd certainly try a power cycle, and I'd try to rule out external impulse interference as a cause of the problem.

I am sure that one of my pvrs had the HDD reformat recommended after a period of time; trouble is, I can't remember if it was the Humax 8000 or the Panasonic DVD/HDD recorder.

I would still go with this advice. Hard disk drives, by their very nature, are random access devices, so files can be spread all over the disc surface, rather than being clumped together.

The fact that fragmentation occurs does not mean it will ever become a problem. PVR filesystems are optimised for large files by having much larger allocation units than a PC filesystem. Caching, together with the modest bandwidth requirements of SD recordings as compared to the performance of a modern hard drive should mean that even heavily fragmented files play back without problems. And of course, if you've deleted all the files (as you presumably would if you no longer wanted them!), a reformat becomes redundant, unless it's to fix problems other than AV file fragmentation.

Still, I'd be interested to know exactly what your PVR manufacturer recommended.

DCJarvis.
Need to be careful as I have suffered similar problems in last 6/7 weeks on my DHD4000. After trawling the internet here's what I believe is happening. Changes at the transmitter (for full digital changeover) are piping the data to the DHD4000 in a way that the DHD4000 can interpret. My understanding is that the DHD4000 needs a s/w upgrade. There are various discussions as to whether the DHD4000 and other boxes are fully digital compliant etc. There may well be a reduction in signal strength accompanied with this change. All I can get are the main channels on mux 1 and 2 whilst A, B, C and D are non existent. My daughter's freeview box, upstairs gets them all so the signal IS there but I just think that the DHD4000 box can't interpret them! Pain in the backside really.

This is my reading of the situation. It does seem odd that by daughter's freeview box picks up the channels no problem. I am going to try her box downstairs connected to the outside aerial and see if that works OK. If it does then it's the DHD4000 that's the problem.

I am unsure if the box will EVER pick up these muxes again or indeed if all it needs is a s/w change.

http://www.ukfree.tv/fullstory.php?storyid=1107051384

Hope this helps. Will update you on how I get on.

Hmm, will give the rescan a go. Playback from a recording is only stuttery if the reception is stuttery, so I don't think it's a HDD issue.


Do you mean electrical interference from other boxes around the DHD4000?

Thanks for the help

Straight away, that suggests that the signal you are getting is insufficient. You should be getting all Mux if you had enough signal. Presumably you don't get the 14 day EPG either.


That difference could be that the TV doesn't need quite as much signal as the 4000 and can (just about) cope.


I think I heard somewhere that Freesat (nothing to do with Murdoch) now had PVRs which operate a bit like 4000 and Sky+.

This sounds like two red herrings. Firstly, the OP is suffering from stuttery reception, not complete loss of muxes. Secondly, there were two types of changes made or planned to the DTT signal, one of which has already happened and doesn't affect the DHD4000, and the other of which is not going to happen (AFAICR) until after DSO, and still won't affect the DHD4000.

Indeed - or from appliances elsewhere in your house, or even outside it...

That's right. Someone suggested that I take the box to a friend's house so that I get the software upgrade and the 14day EPG. Does this sound like it would work if my signal's not up to scratch when I get the box home?

You aren't getting Mux D. You won't get the firmware update now because it's no longer being broadcast. Have you never received the EPG? I must admit I assumed you would have mentioned that in your first post, since you've had the box for a few years!

Not really, as the EPG is retransmitted every night on Mux D at 0300, so unless you left it there overnight about once a fortnight, you would soon find it was totally out of date.

As for the upgrade, as njp says, the last one was so long ago (May 2006) that there isn't much chance of it still being sent. Don't know if Inview would do it on request, but you would have to make sure you were getting Mux D reliably first.

OK chaps, sounds like I need to be investigating freesat rather than trying to get anything more out of the DHD 4000. Shame... If anyone is looking for a spare machine then give me the nod!

Don't give up yet. What part of W. Sussex are you in, and which transmitter are you using? I am in Crawley, using Crystal Palace, however there are lots around here who use Reigate, but in some areas of town it isn't quite good enough for digital. Could your problem be something like that I wonder?

If you are suffering from poor reception..

.. check your PSU Capacitors are not bulging.

As these parts fail they add electrical noise that disturbs the tuners. If they are bulging get some good quality replacements soldered in (Farnell, RS etc).

I'm near Billingshurst and pointing at the Midhurst transmitter. Well that's what I thought... the Thomson tuner is set to 61, and it's coming up as "south." which is a little confusing.


Hmm, sounds a bit tricky!

1. Unplug the box.
2. Take the top off
3. Identify the small PSU board
4. Look at the tops of the two biggest capacitors, one each side of the mini transformer.

Q1. Is the top flat and no leaks? Good.
Q2. Is the top curved outwards or you can see leaks? Bad.

Agreed.
If it is using the Linux EXT2 file format then fragmentation is not an issue anyway.

The Thomson boxes suffer with disk format errors - which are an entirely different thing. This is when the information on the disk filing system (only visible to the OS) is incorrect. Usually a linux system fixes this by:

a) Avoiding this issue by using EXT3 - a journalling file system that has a few modes but in general uses more CPU but guarantees the file system is always consistent.

b) Running FSCK (e2fsck in fact) on any disk that has an expired start-up count or is not marked as clean.

An OS will occasionally do a Sync operation that makes the disk consistent and sets the clean bit. Any disk write is otherwise incomplete and resets the clean bit.

The Thomson TUTV PVR uses the EXT2 file system but consistently fails to use the clean bit and never repairs the disk format. Every single crash and power down adds more faults to the filesystem until the system is so unreliable you are forced to reformat.

I myself take the disk out and run e2fsck -fy on the 2 partitions affected - to maintain my program library and repair the damaged disk format information, but not everyone can do this.

It is reasonable to assume that if reliability falls off after much use then then you are suffering system crashes due to damaged and invalid file systems - which mislead and confuse the OS and the application leading to further crashes and further damage. Without any FSCK disk repair it in inevitable that you will reach a point of unusablility and be forced to reformat.

Problem is the DHD4000 doesn't use EXT2 or EXT3, it has a custom file system, so any Linux FSCK routines wouldn't work.

Matt

Yes, that is confusing. There is nothing wrong with it being labeled "south", however UHF Channel 61 is not used by Midhurst at all. You might like to check exactly what you are receiving.

Which of the following TV channels do you see on the list of those available?

BBC1
ITV1
five
BBC Parliament
Sky Three
Film4

These are one for each Mux and will tell us which Mux are missing.

When you are in the Technical Help menu showing the UHF Channel numbers under the picture, which numbers show evidence of a signal (you can scroll through them with the left/right arrow keys)?

The correct UHF Channels for Midhurst are:

56 (Mux 1 - eg. BBC1)
65 (Mux 2 - eg. ITV1)
62 (Mux A - eg. five)
59 (Mux B - eg. BBC Parliament)
64 (Mux C - eg. Sky Three)
60 (Mux D - eg. Film4)

For info, the only transmitter using 61 and in "south" is Whitehawk Hill at Brighton for Mux D (which you don't seem to be receiving anyway!).

Final thought. When you mention 61, I take it you are not talking about the "rf modulator" channel in the "TV Setup" or "Technical Help" menus. If you are, then move it well clear of the 50s and 60s as that would be likely to cause all sorts of problems with Midhurst.

Oh it will use some standard filing system, not a custom one.

Are you aware of the effort that goes into designing a robust file system? And then the software to use it and manage it? (Clue - it's a great deal more than the effort of writing some PVR software... and rather pointless if a proven format is sitting there ready for the taking)..

What is it then? And at what point does "custom" becomes "standard"? Certainly, we know (because people have written software to examine it) that the DHD4000 filesystem is very similar to that of several other PVRs, which obviously makes sense. But the point here is that a PVR filesystem has to deal only with a much more limited range of file types than a general purpose computer, so optimising it for those types seems like a good idea.

I have no in-depth knowledge of PVR filesystems, but I have in the past helped to design and implement a robust "custom" filesystem for a specialised application, so I'm not entirely ignorant of the effort involved.

Thomson use ext2 so I would not be surprised if the DHD4000 is also ext2. Filetypes are also irrelevant for a file system TBH - there are only two types, long files and short files

To find out you need to take the disk out, set it to master, plug it into a USB adapter and then into a machine running a modern Linux. Then type df or mount and it will tell you what it is.

Given that the disk lacks a standard boot block, I rather doubt this. However, I have no plans to remove one from a machine to test your theory anytime soon!