I have just received an email from Thomson Broadband UK Ltd saying "See attached file for retune procedure". It read as follows:

====================================
Model Number
DHD4000

Symptoms
Picture breaks up and sound clicks on some channels

Cure
1 Disconnect aerial cable from back of unit
2 Press Menu Button
3 Press OK Button
4 Select scan for channels
5 Press OK Button
6 Press green button- wait for scan to complete and will see found 0
7 Press red button to cancel
8 Select Technical help
On the right hand side of menu you will a see blank screen and underneath
1: and a number will be highlighted.
9 Press left or right Button(next to OK button) to select 62
10 Press OK Button
11 Press Left button to select 61
12 Press OK Button
13 Press Left button to select 59
14 Press OK Button
15 Press Left button to select 58
16 Press OK Button
17 Press Left button to select 55
18 Press OK Button
19 Press exit button to exit all the menus until picture appears
========================================

The channel numbers; 61, 62, etc. appear to relate to the Winter Hill transmitter in the North West.

If you follow the instructions then you are manually tuning to each mux in turn, thereby avoiding the picking up of any signals from other transmitters in the area, e.g. Moel y Parc.

On my box it is essential to wait until some signal strength and a picture above is shown before moving on to the next channel.

This response from Thomson appears to support their view that the problem is related to overlapping signals from two separate transmitters.

Unfortunately I had already tried this manual tuning procedure some days ago, and it has not fixed the problem. I continue to believe that the problem is related in some way to the new transmission standard following digital switchover.

In the meantime the DHD4000 can still provide some use in a limited form. See this thread http://www.digitalspy.co.uk/forums/s....php?t=1183818

My version of this problem was this: after the two retunes, everything seemed ok for some time, then changing channels started sometimes not working.
Instead of the selected channel, there was just a blank screen, no sound.
Bringing up the guide and removing it got the picture and sound back. Most times doing channel - then + would get it back.
There was no green square as the guide page appeared, it only appeared a moment later, also, with a picture present and pressing OK, there was only one green square.
Once back, the picture was stable and quite ok.
Doing an auto retune, the 4000 could only find 1 or 2 frequencies instead of the usual 5.
A Hitachi PVR and a TV have both retuned without any problem, but another 4000 (both have new psu caps) behaved in exactly the same way.
This seemed to indicate that the 4000s weren't faulty in the sense of something having gone wrong, just having difficulty with the tuning since the switchover.

Doing the manual retune, as above, did work and it's all perfectly ok now, typically signal strength 7, quality 9, no break-up or any other problem.
I'm in south Manchester, 16 miles from Winter Hill with no obstructions to line-of -sight.

Obvious point, but the instructions don't actually have the line 'replace the aerial' ! (should be between 7 & 8 in the list)
You DO have to wait, for each frequency, until a picture appears. Be patient, it's not stuck, it's scanning that frequency.

So it seems it's the transmission changes, not a faulty tuner or anything else in the 4000, and persisting with the manual tune process should be tried before hardware changes/binning it!

I also received the retuning procedure email from Thomson. I tried it on both my 4000's but it did not cure my picture and sound breakup problems. After about 30 minutes on the phone to them (they tried to be as helpful as they could) we both agreed to concede defeat.

I am not using either box now, they are still plugged in but I am now using two Humax 9200's, which although they have their own problems, are useable.

My location is also S. of Manchester in Macclesfield.

The link to the method of using just the best tuner in the 4000 is interesting as I have found that with mine the breakup is always worse on one of the tuners.

The above retune method worked for me; since the DSO I've added a variable antenuater plus a another old one that I had hanging around, it improved things a little but still got breakups, now all seems fine.

Further to my earlier post, other DHD4000 owners experiencing problems, and whose boxes have the Tamura power supply rather than the Samsung one, may be interested in the following:

After finding that the tuner 1 problem resolved when the power supply was cooled, I managed to pin it down to one of the two Schottky barrier rectifiers; the one nearer the edge of the box marked SR540. This felt quite hot to the touch, and when it was cooled the tuner problem disappeared.

The components in question are:
Mfr unknown but mark is a large W. SR540 5amp 40v measured voltage 3.2v (nearer edge of box)
Mfr Taiwan semiconductor (TSC). SR306 3amp 60v measured voltage 5.6v (nearer main board)

I suspected that these two components could be interchangeable. They could be different specs from different mfrs, but near enough for the requirement. (Can't be sure though!)

Anyway, I decided to desolder and swap them over. Having done this, although the one now nearer the edge of the box (SR306) runs hot like the other one, the problem seems to have resolved. Both tuners are now working fine with no picture or sound breakup at all.

RC4,

You encouraged me in your last post to take the top off my two 4000's which are now unuseable because of picture breakup. Unfortunately I find these both have the Samsung power supply.

Do you know what voltage supply lines these shottky diodes were in, in your psu?

Also, where did you measure the voltages you give?

Were the diodes mounted on a heat sink?

I'd really like to find a repair rather that throw these two units away.

None of the capacitors in my supplies look swollen.

Here is a link to a photo of the Tamura power supply http://farm5.static.flickr.com/4029/...2b658eb8_b.jpg

I'm afraid I don't know which voltage supply lines they related to. I measured the voltages across each diode. The diodes in question are marked as D12 and D13 and can be seen to the bottom right of the large transformer in the middle of the psu. No heat sink.

My box has been working perfectly since, so I hope you are able to get yours fixed.

Thank you very much for your reply.

I have found on my Samsung PSU that there is a heat sink with two diodes in TO220 cases mounted on it. One is a single diode FES8T 8A 70v and the other is a double diode SBL1040CT 28V 2 x 5A. Maybe these serve the same function as yours.

Do you have a type number on your Tamara supply? If you do, I might be able to track down a schematic.

Peter

The only identifying marks are "Made in China Tamura - R40085 Rev 00". I tried myself to find some reference to this by searching on Google, but without success.

But good luck anyway.

One other thing. At one point I had the same problem as you, with both tuners exhibiting bad picture and sound breakup. I fiddled with the wires connecting the psu to the main board, basically just a poke with the fingers, and hey presto the problem disappeared! So, obviously it's possible to have a poor connection here which can cause problems.

Just a post to bring things up to date with my failed efforts to get my two DHD4000 working post Winter Hill DSO.

They both have picture and sound breakup despite manual retunes and adjustments of signal strengh using two fixed aerial attenuators and a Maplins variable attenuator.

As a final attempt I tried fitting new capacitors to the Samsung power supply using a Satcure power supply repair kit. I also added a thick earthing strap from the power supply connector to the case of both tuners. There was possibly a little improve ment but the breakup was still unacceptable.

In desperation, I thought I would give it a go and replace all the capaciitors on the main board with new 105 degree versions ( there are about 50). After doing this I was surpised that it still worked......but unfortunately the problem still existed. I think the bin is now the only place for these two boxes.

I loved the DHD4000 but then I went down the Topfield route. I bought a 5800t for £120 and once I'd loaded mystuff 6.1 never looked back. The DHD pretty much came out of circuit the next day (demoted to SCART 2 from SCART 1).

When I pick something off the archive to playback it has 3 minutes of prior padding and 6 minutes of post padding but the accurate record TAP means the programme plays back from the start credits when I hit "ok" and I don't have to spool through the start padding (at least for BBC stuff!).

I went on to buy one of the refurb diskless 5810's off ebay for £79, supposedly for my parents, added a SATA adaptor and 160GB 2.5" disc and I'm more impressed for the front display and general speed of the device. The DHD4000 got unplugged much sooner than I expected and I'll probably give my parents that instead ...

Only Topfield annoyance which can't be sorted is it taking control of the TV via the SCART as it powers up for timer events. It's frankly a ridiculous idea that it should assert power on the SCART during timer events, it should pretend to be asleep until you press "power". Other than that the DHD is done for me I mourn it passing but the Topfield is just better in pretty much every way.

No doubt if the DHD had continued to be developed it could have challenged the newcomers to the market but for me the Topfield is the way to go. I rarely set timer events these days, it has them all cached within the power search engine and they just return week after week even if the programme moves.

Slimgym,

I've been checking up on the specs for the topfields and I cannot tell from what I have read if both the 5800 and the 5810 have UHF modulators. Is it only the older 5800 that has one or does the newer 5810 have it as well?

I ask because I find it nice to distribute the signal to other rooms in the house using a coax connection.

Perhaps you would be good enough to check yours for me?

I see that 5810's are available new from Lewis's and MicroDirect but if I needed a 5800 to get a modulator I would have to buy second hand, which I am not keen on doing.

Yes only the 5800 has a modulator. The 5810 has no modulator, but does have HDMI out (which the 5800 doesn't). You could always add an external modulator?

I'm with you one the second hand thing though, there are reports of early ones having power supply issues. They do occasionally crop up brand new on ebay - mine was like that only back in november. I'd keep an eye out for those instead to be honest. The one I have doesn't look anything like the black or silver plasticky ones you see on ebay, it's got a shiny silvered front with a large silver button in the middle.

I've been getting the same breakup problems after our region's switchover, currently we are between phase 1 and 2 so only the BBC A mux has gone full power at the moment, but all the BBC TV channels have the problem.

Mine has the Samsung PSU (capacitors replaced over a year ago) so I can't try the diode swapping trick. There is no point in trying additional grounding between the tuners and PSU as both are well-bonded to the case already.

Then a chance breakthrough, of sorts. I had been trying the box using a handheld aerial (full size, Yagi contract type, band C/D) pointing out of an upstairs window, to isolate it from any noise in my aerial distribution system, and was still getting the breakup problem on both tuners. Then... as a shot in the dark I tried reverting to version 1.7.7. Result: rock solid pictures on both tuners. However it is very sensitive to the signal being too strong or weak, there seems to a sweet spot around signal strength 5 and quality 7-8. I've not been able to get a stronger signal from the flying aerial but on reconnecting the box running 1.7.7 to its normal roof aerial (log periodic with integral amp), which gives a strength of 10 and quality of 9 on the new BBC mux, the picture was back to breaking up again. Taking the flying aerial off line to make the signal weaker made the picture break up again immediately. Taking the box back to 2.3.9 when 1.7.7 has stable pictures yields picture breakup again, so the software release consistently makes a difference.

So it looks to be software-related, perhaps we can build up support to see if Thomson will fix this. I would be loathe to get rid of it as it does quite a few things which even recent PVRs don't (especially buffering the previous channel as well as the current one).

In any case it would be interesting to hear if anyone else can repeat this behaviour.

Additionally, it would be useful to know if anyone else's DHD-4000 displays repeated horizontal flecks either side of the video box when in the signal strength screen, pulsing about once a second. Mine does but only when tuned to a post-DSO 8k mode mux, there are no flecks when tuned to a low power 2k mode one.

This is almost certainly related to the problem as the picture breakups seem to be timed with the flecks.

The final solution, for me at least, for the 8k post DSO breakup problem has been to hard solder the PSU (Samsung) to the main board. Previously both tuners would break up no matter how much the PSU connectors were re-seated, now they don't at all.

So the DHD-4000 **can** work with post-DSO 8k mode but you have to get your hands dirty.

Thanks tjhewitt for your updates. You've given me new hope.
I'll certainly try the direct soldering of the psu to the main board. Did you find this was needed AS WELL AS your change in the version of software?

BTW how do you change back to an earlier version of the software? Does the box store an earlier version?

Are you back on the main aerial now and getting no breakup?

Can' t comment on the picture flashes on the tuning screen, as here, on Winter Hill, all signals are now 8K.

Peter

Only the direct PSU soldering was needed, I'm still running the latest 2.3.9 version with the main outdoor aerial, signal strength 10, quality 9 on both tuners for the BBC A mux (the other muxes are still at pre-DSO state, for the next week at least). The box stores the current version and the previous one, you can switch between them in the technical help/signal strength screen ("restore s/w").

Beware that the Samsung board rectifies the AC at 240V, not after it has been transformed to a lower voltage. This means that the heatsink of the 3-legged "chip" next to the large capacitor is at high voltage, but DC so you won't feel it you'll just fry silently. So be careful if you power up with the lid off.

Sorry to say that directly wiring the psu to the main board has not worked for me.

Receiving BBC 1 there were still some halts in the video for 1 or 2 seconds and the audio had the odd click. As I was on the latest 2.3.9 software, I reverted to the older 1.7.7 but the reception was the same. I then added a 6db attenuator to the input and this did give a good reception for 5 minutes with no break ups on BBC1, but changing to ITV 1 the problem was back. Further tests checking which tuner was in use, for what channel, indicated that only tuner 1 was capable of receiving a fault free picture. ( I have always noted that the performance of tuner 2 was inferior to tuner 1).

In an attempt to even out the performance of tuner 1 and tuner 2 , I tried removing the connecting bridge on the back and inputing the aerial directly to tuner 2 and looping back with a coax lead from 2 to 1. This made no difference. Tuner 1 still showed s9 / q8 and tuner 1 s7 /q7.

In desperation to see what I needed to do to tuner 1 to bring down the reading I added a 9db attenuator to the coax loop back. This got the signal strength down to 5 on tuner 1 but the quality was still surprisingly 8. I think this shows that there is someting more to getting a good quality of signal than just signal strenght. Tuner 1 seems to be inhrently better at doing its job that tuner 2 (this was showing s7/q/7 at this time).

Its all too confusing for me!

I think if you are lucky enough to have 2 good performing tuners in your box then you may get satifactory reception ....but thats not mine.

I've since found that mine still has "moods", in that it can be perfect for hours then start breaking up as badly as it ever did, then get better again. 80% of the time it seems fine, certainly better than when it was bad 100% of the time.

It may be worth replacing the 3-legged IC on the high voltage side of the PSU as according to satcure.com these can cause "tripping" problems, which may be smoothed out by all the other capacitors on the low voltage side but only "just". So some may still have problems and others not. I wonder if decoding 8k mode takes more power and so pushes the PSU further.

slimgym,

You can stop devices taking control of the TV by disconnecting pin 8 in the SCART plug. You'll have to manually switch the TV to the required input when you do want it, but this may be a preferable arrangement.
If you need detailed instructions email me - banzolfang@btinternet.com - and I'll send you step-by-step with pictures.

Many thanks - I had considered that, but it would also stop the auto wide screen switch too so that would need manually correcting It's an infuriating and pointless downside to what is otherwise a nearly perfect machine (with mystuff that is). There is a firmware patch to auto-disable that takes a few seconds to kick in. I'd considered putting together a circuit to "abosorb" the delay period and only pass on the 12v if it stayed there beyond that time but so far I've not got around to it, hoping Topfield would firmware correct it!

The DHD4000 seems to include wss switching via the line blanking signal as well as the scart control. I'd be surprised if the Topfield doesn't also do the same, so you might still get wide switching even without the scart control, provided your tv can deal with it of course.

My TV has the option to turn off auto Scart switching, this is very useful with Toppy's, and still allows auto wide screen switching.

Have you tried connecting your Toppy to a different input on your TV such as S-VHS or Composite AV. These will not take over your TV when the Toppy comes out of standby.

I have one Toppy connected via Scart, and one Toppy connected via Composite AV, and they both auto wide screen switch properly.

Well I didn't expect my 2004 Sony 36" CRT to have WSS detection but on plugging the DHD4000 into the front composite input it does indeed switch when I hit the "wide" button on the DHD. Brilliant, thanks both