I've just put the 160GB "upgrade" hard disk back in and the breakup has come back. It had been running with the original 40GB one for a few days because the 160GB upgrade blew up its PCB (long story) - even then the picture still broke up until the PSU was hardwired but now, even with that, the breakup has come back with the 160GB HD. Does yours have an upgraded drive too?

I tried powering the 160GB drive separately to relieve the PSU but for some reason the DHD-4000 wouldn't boot, probably just needing better grounding between the PSUs.

I happen to have an old 40GB laptop 2.5" drive (and large to small IDE connector adaptor) and the DHD-4000 is currently running with it with no picture breakup at all on either tuner. Since this drive draws nothing at all on the 12V supply, and probably less on the 5V too it is giving the PSU less to struggle with. We now have the ITV/C4 mux at full power since yesterday and that's clean as well as BBC A. The COM muxes are still at pre-DSO levels (10kW rather than 100kW).

For me this confirms that the Samsung PSU is the problem regarding the 8k mode breakup, it just isn't up to the job. I'm going to try changing the 1M0380R chip to see if it lets the 160GB drive work without breakup, which I'll post about once that's done, otherwise it looks like one solution is to use a 2.5" drive. It might be the case that providing a separate 12V supply to a 3.5" drive and leaving the 5V one being supplied by the DHD-4000 (or perhaps just provide better shared grounding beyond that provided by the IDE cable) will allow the thing to boot and run without breakup, hard disk PSUs are cheap... At least we'd be able to keep our DHD-4000s going a bit longer rather than having to bin them even if it means drilling a hole in the case to get the external supply in.

One thing which seems to be a true 8k mode bug is a blank screen when first tuning into an 8k mode mux, worked around by going into the first menu level then exiting it.

Hmmmmmm. Your experience seems to confirm that the PSU is connected to the picture breakup. My two 4000's still have the original drives. I do have some little self contained psu's that will power an ide drive so I could try one of those as a way to reduce the load on the psu.

Peter

I just tried that, this time making an effort to provide proper grounding between the two supplies. The disk refused to spin up. Then tried providing just the 12V supply from the external PSU leaving the Samsung PSU to provide the 5V, since the IDE bus is referenced to 5V, still no go.

So here success is hanging on the 1M0380R IC. For now the DHD-4000 is back running on the 2.5" drive, still perfect pictures.

I was pretty much set to get a Topfield after soldering the PSU to the motherboard, having already replaced the capacitors.
I am pleased to report that my DHD4000 is 99% back to normal after swapping back to the original 40Gb Seagate drive. There is only a very occasional macro block fleck in the picture and the sound was perfect when I tried it out last night.

If recording space becomes an issue then I will buy a 160Gb 2.5" drive, though on paper they don't appear to have power demands much different from the 40Gb Seagate which is odd (I was looking at the Samsung HM160HC available for £43 on scan.co.uk).

I tried a 2.5" drive, one of the WD 160GB scorpio blue range, and the USB-SATA adaptor from Dealextreme, when my 120GB WD drive gave up the ghost. It didn't seem to be able to keep up with the throughput when spooling through programmes and the DHD4000 would crash with all the LED's still spinning but a frozen screen picture. In the end I put the original drive back in to restore normality. I don't recall it crashing in normal playback or standby.

I kept the WD 160GB and interface, and put them into a Topfield 5810 when Turbosat were selling them at £79. It works fine in that but then the maximum FF/RWD speed is about 16x not 64x ...

Reporting back as promised on changing the 1M0380 IC on the PSU. I put a new one on from signalsuk, £3.49, no discernable difference. It still wouldn't run glitch-free with the 3.5" 160GB 7200rpm upgrade drive when tuned to an 8k 64QAM mux, 2k muxes were still ok. I managed to get the same disk to spin up and respond with it being powered from an external PSU, oddly still no improvement at all to the glitches.

In the interim the box has been running with an old 80GB 5400rpm 2.5" laptop disk and was glitch-free when watching live but not when using the buffer or playing back recordings, this turned out to be the 18" IDE cable that was being used to connect it. Using the short one that comes with the DHD-4000 has fixed this, it seems that it was having trouble driving the signal down a normal length ribbon cable.

For now the unit is working perfectly on all muxes, not a glitch seen all day.

So it looks like the ultimate solution is to use a 2.5" laptop disk. Whether it is still necessary to hardwire the PSU to the motherboard is not known, perhaps someone who hasn't done that yet can try the 2.5" disk approach first and post the results.

I've had a couple of private messages with tghewett, and as a result I have copied his advice. I bought a Samsung Notebook Hard Disk 2.5 Inch Drive 160GB IDE from R U SMART TRADING LIMITED through Amazon for £42.50, and a 3.5" IDE - 2.5" IDE Laptop HDD Adapter Cable from CDL Micro again through Amazon for £3.99. All you have to do is remove the 3.5" drive from its plastic caddy, and disconnect the ribbon cable and the power cable. Next connect the adapter cable to the main board, and connect the power supply cable into the adaptor cable. I was unsure which way to connect the adaptor cable to the new 2.5 HDD, as this one is capable of being connected either way round. Obviously if you get it wrong you are likely to fry the HDD. Tg advised me to have the power connection at the opposite end from the four jumper pins on the HDD, or to put it another way, the power goes into the HDD at the far point from the front of the Thomson, if you have mounted the HDD with its label uppermost. If this is not clear send me a message and I'll email a photo. Once connected I fixed the new 2.5 HDD into the caddy using sticky tabs.

I have just tried it out and the reception is now greatly improved, and I would describe it as 95% of perfect. I still get the very occasional freeze or blockiness, and sound glitch, but not enough to be a problem. The reception had become totally unwatchable, but is now fine, if not perfect.

i should add that I have not hardwired the PSU to the motherboard.

I'm going to try it out for a week, to see how good the recordings are on different channels, and then hopefully upgrade my other Tommy the same way. This way I can postpone buying new machines until the HD models become cheaper (and hopefully reliable).

The lack of EPG is still annoying, but I can live with it.

My heartfelt thanks to tghewett, who has been prompt and helpful with his advice.

Colin.