The Pye D18T is (almost) done - UK Vintage Radio Repair and Restoration Discussion Forum

Ian B · 25th Oct 2007, 6:14 pm

Greetings Sages,

Thanks to all the encouragement from you wonderful people I can now present two shots of the D18T in operation. Pictures aren't too brilliant owing to flash glare, but I think they convey the fact that the set works. Obviously a bit more still to do (picture is slightly rotated clockwise) and hum bar travels slowly down the screen (new 100uf smoothing cap arrived today, already changed the 60uf reservoir cap, hope that will sort it).

However(as usual), there are still some other niggles. After about 40 minutes from switch on, the picture is well out of focus. It starts a bit blurred from cold, and improves to good after about 10 minutes (I haven't managed to work out how to free the adjustment, it seems very stuck!) Also when the focus has gone , the picture has moved off centre to the left.

Thanks,

Ian Blackbourn

Steve_P · 25th Oct 2007, 6:25 pm

This might prove useful.... https://www.vintage-radio.net/forum/...ad.php?t=11535

Spray the focus control and tube neck assembly with Servisol and wait for about an hour. Then move things slowly.

Cheers,

Steve P

Ian B · 9th Nov 2007, 10:16 pm

Well, I seem to be getting there...almost.

I ran Test Card C for an hour this afternoon and the focus stayed good. This after having replaced the EY51 and adjusting the focus after 15 minutes running yesterday. So definite improvement there!

However, the problem I haven't been able to cure is hum on vision. Dark band (s) moving down the screen, as one reaches the bottom, another appears at the top. They start at the centre, barely moving, then as it warms up the rate of progress increases.

I've fitted new reservoir & smoothing caps, and every other electrolytic except the cathode bypass on the sound output valve. (There's no significant hum on sound, by the way)

I've checked all the valves on my valve tester for heater-cathode leakage, all ok.

I've tried different PL38, PY31 and PZ30, no improvement.

EHT smoothing is apparently by using the aquadag coating on the tube - could that be the problem? And if it is, what can I do?

In desperation (and ignorance)

Ian Blackbourn

Danny · 10th Nov 2007, 11:24 pm

Hi
It's not likely to be the EHT smoothing, as this is derived from flyback.

The problem could be down to your signal, and entering via the cables from your converter, so this is worth checking.

If you feel its down to the set, then you will have quite a task on your hands. This can be caused by a slight h/k short in a valve, smoothing or an earth loop.
I would first try an isolator in the aerial lead; also try attenuating the signal to see if the hum bars are reduced: if yes, then it's probably to do with converter problems.
I'm not saying the converter's faulty, but I have had this, and it's been the good old earth loop.

Danny

Steve_P · 10th Nov 2007, 11:49 pm

You don't have to connect it directly to the set you know. Just put an insulated loop of coax out from the modulator and fashion an aerial from the set.

Cheers,

Steve P.

Sean Williams · 11th Nov 2007, 10:32 pm

Ian,

The Aurora certainly has a fearsome RF output - might be worth trying a 6-10db attenuator on the output.

MFT in Lower Stondon will be able to supply you with something suitable for a couple of quid

Sean

Ian B · 17th Nov 2007, 1:58 pm

What does Steve P say ? - always recheck your work. He's right again!

After I'd replaced all the wax caps and before switch on I checked all the slider controls on the back of the chassis - all ok.
Having fitted an attenuator in the aerial lead (thanks for the info Sean) I was trying to adjust the brightness and found that it went from too bright to too dark with a sudden jump. Faulty pot I thought, and sure enough, there's a break in the VERY thin wire.

So I've rigged up a temporary 10K ww pot on a bracket off the chassis, held by two existing screws. Switch on Test Card C, no black band; excellent!

I've just watched a short film on tea making, and part of the BVWS dvd about Mullard valve manufacture, probably about 45 minutes in total, and although it's not quite perfect, it's perfectly watchable, and it still stays in focus (so far!).

I can't really work out when the slider pot went o/c. Initially I had been able to adjust the brightness, although it did seem a bit "jerky", and the hum was hardly noticeable then. I think the slider was able to bridge the break originally until I disturbed it again.

Anyway, I'm hoping this is almost a Success Story now!

Regards to all

Ian Blackbourn

25th Oct 2007, 6:14 pm	#1
Ian B Hexode Join Date: May 2006 Location: Arlesey, Bedfordshire, UK. Posts: 401	The Pye D18T is (almost) done Greetings Sages, Thanks to all the encouragement from you wonderful people I can now present two shots of the D18T in operation. Pictures aren't too brilliant owing to flash glare, but I think they convey the fact that the set works. Obviously a bit more still to do (picture is slightly rotated clockwise) and hum bar travels slowly down the screen (new 100uf smoothing cap arrived today, already changed the 60uf reservoir cap, hope that will sort it). However(as usual), there are still some other niggles. After about 40 minutes from switch on, the picture is well out of focus. It starts a bit blurred from cold, and improves to good after about 10 minutes (I haven't managed to work out how to free the adjustment, it seems very stuck!) Also when the focus has gone , the picture has moved off centre to the left. Thanks, Ian Blackbourn Attached Thumbnails

25th Oct 2007, 6:25 pm	#2
Steve_P Dekatron Join Date: Sep 2003 Location: Bolton, Greater Manchester, UK. Posts: 6,644	Re: The Pye is almost done This might prove useful.... https://www.vintage-radio.net/forum/...ad.php?t=11535 Spray the focus control and tube neck assembly with Servisol and wait for about an hour. Then move things slowly. Cheers, Steve P __________________ If we've always had it, why is the Car Boot open? You're not sneaking another Old TV in are you...?

9th Nov 2007, 10:16 pm	#3
Ian B Hexode Join Date: May 2006 Location: Arlesey, Bedfordshire, UK. Posts: 401	Re: The Pye is almost done Well, I seem to be getting there...almost. I ran Test Card C for an hour this afternoon and the focus stayed good. This after having replaced the EY51 and adjusting the focus after 15 minutes running yesterday. So definite improvement there! However, the problem I haven't been able to cure is hum on vision. Dark band (s) moving down the screen, as one reaches the bottom, another appears at the top. They start at the centre, barely moving, then as it warms up the rate of progress increases. I've fitted new reservoir & smoothing caps, and every other electrolytic except the cathode bypass on the sound output valve. (There's no significant hum on sound, by the way) I've checked all the valves on my valve tester for heater-cathode leakage, all ok. I've tried different PL38, PY31 and PZ30, no improvement. EHT smoothing is apparently by using the aquadag coating on the tube - could that be the problem? And if it is, what can I do? In desperation (and ignorance) Ian Blackbourn

10th Nov 2007, 11:24 pm	#4
Danny Heptode Join Date: Jul 2003 Location: North Walsham, Norfolk, UK. Posts: 516	Re: The Pye is almost done Hi It's not likely to be the EHT smoothing, as this is derived from flyback. The problem could be down to your signal, and entering via the cables from your converter, so this is worth checking. If you feel its down to the set, then you will have quite a task on your hands. This can be caused by a slight h/k short in a valve, smoothing or an earth loop. I would first try an isolator in the aerial lead; also try attenuating the signal to see if the hum bars are reduced: if yes, then it's probably to do with converter problems. I'm not saying the converter's faulty, but I have had this, and it's been the good old earth loop. Danny Last edited by Mike Phelan; 28th Jul 2008 at 11:41 am. Reason: S&P

10th Nov 2007, 11:49 pm	#5
Steve_P Dekatron Join Date: Sep 2003 Location: Bolton, Greater Manchester, UK. Posts: 6,644	Re: The Pye is almost done You don't have to connect it directly to the set you know. Just put an insulated loop of coax out from the modulator and fashion an aerial from the set. Cheers, Steve P. __________________ If we've always had it, why is the Car Boot open? You're not sneaking another Old TV in are you...?

11th Nov 2007, 10:32 pm	#6
Sean Williams Dekatron Join Date: Feb 2005 Location: St.Ippolyts, Hitchin, Hertfordshire QRA IO91UW Posts: 3,517	Re: The Pye is almost done Ian, The Aurora certainly has a fearsome RF output - might be worth trying a 6-10db attenuator on the output. MFT in Lower Stondon will be able to supply you with something suitable for a couple of quid Sean __________________ Engineers make things work and have spare bits when finished

17th Nov 2007, 1:58 pm	#7
Ian B Hexode Join Date: May 2006 Location: Arlesey, Bedfordshire, UK. Posts: 401	Re: The Pye is almost done What does Steve P say ? - always recheck your work. He's right again! After I'd replaced all the wax caps and before switch on I checked all the slider controls on the back of the chassis - all ok. Having fitted an attenuator in the aerial lead (thanks for the info Sean) I was trying to adjust the brightness and found that it went from too bright to too dark with a sudden jump. Faulty pot I thought, and sure enough, there's a break in the VERY thin wire. So I've rigged up a temporary 10K ww pot on a bracket off the chassis, held by two existing screws. Switch on Test Card C, no black band; excellent! I've just watched a short film on tea making, and part of the BVWS dvd about Mullard valve manufacture, probably about 45 minutes in total, and although it's not quite perfect, it's perfectly watchable, and it still stays in focus (so far!). I can't really work out when the slider pot went o/c. Initially I had been able to adjust the brightness, although it did seem a bit "jerky", and the hum was hardly noticeable then. I think the slider was able to bridge the break originally until I disturbed it again. Anyway, I'm hoping this is almost a Success Story now! Regards to all Ian Blackbourn