Pye D18T. - UK Vintage Radio Repair and Restoration Discussion Forum

EF80TVVALVE · 12th Jan 2023, 8:17 pm

Hi all

I picked up this D18T from Courtney Louise a few weeks ago, it's a welcome addition to the collection having had one many years ago that I had to pass on due to lack of space, one of the sets I wish I never had sold!

It did have a fault with a lack of signal which I traced to a few wax capacitors hiding in the RF section. After these were replaced I finally had a picture. The contrast control on the front is very sharp and only works towards the upper end, turning back more than a quarter of the way causes loss of signal so I need to investigate further.

Today a new problem developed. I'm attempting to get the picture centred better as it's a little too far over one side and the adjustments don't bring it in properly. Whilst adjusting the hardware around the neck the set suddenly lost all sync of the picture. The picture has lost frame hold just leaving a test card scrolling upwards, the line hold is also a bit unsteady but better than the frame hold. The picture also scrolls sideways on the screen. Oddly adjusting the volume control alters how much the picture collapses and rolls and there is an intermittent hum on the sound too.

There are still a few original components in the set, I presume one of these has suddenly gave way causing the described fault. Just before I start poking around I just thought I'd ask any suggestions that may lead me in the right direction.

Thanks all!

mark pirate · 13th Jan 2023, 10:30 am

I had similar problems when restoring my D18, at first I replaced the PZ30 & PL38, this improved matters, but changing the 100/60uF smoothing can fixed the problem.

I had a similar contrast problem with my BV30, it was either on or off, changing the pot gave me more range & smooth operation.

Mark

EF80TVVALVE · 13th Jan 2023, 11:14 am

Thanks Mark, I managed to trace the fault to the 8uF 125v electrolytic (C17A) that had become a dead short, just by chance it happened whilst I was making adjustments. With this replaced I now have a picture again, still too far shifted over one side so I may look at the timebase components and make sure that everything is okay around there.

There are some hum bars on the screen so I need to investigate this too, but it's nice to have a picture back on there!

EF80TVVALVE · 14th Jan 2023, 10:30 pm

Some more fettling with the D18T today, I managed to spend some time removing the magnet assembly for the CRT. There are two rubber bumpers, basically some cut rubber hose that are used as a spring to keep the magnet up against the adjusting thumb nuts. These had deformed into their cramped up state so they were no longer providing that spring effect for the magnet. Some time in hot water and stretching them somewhat before re-fitting slightly rotated has returned a good amount of adjustment for the magnet.

Whilst this is all good unfortunately it hasn't solved the problem with the shifted picture as I've attached a photo of. If I adjust the line hold control I can just about centre it before the image collapses so I'm going to look at this area of the circuit for any dodgy components. As can also be seen, there is some shadowing to one side of the picture which is down to the positioning of the rear magnet.

Another thing I noticed is that the scan coils are way over one side and out of adjustment of the locking screw which has been removed in order to extend the range of the coil rotation and centre the picture. I wonder if the CRT fitted just isnt a very good match for this D18T, if that's even a possibility. I do have another set I can borrow the CRT from in order to see if this changes anything.

For now I'm going to focus on getting the picture centred better and go from there.

high_vacuum_house · 14th Jan 2023, 10:39 pm

With the picture offset to the left, I wander if you have some standing DC current flow through the line deflection coils causing this? Maybe a capacitor around the line output valve is leaking?

Christopher Capener

Techman · 15th Jan 2023, 1:13 am

I agree that if it's not some sort of physical alignment type issue then it's likely to be a DC shift caused by leakage through a crucial capacitor.

EF80TVVALVE · 15th Jan 2023, 2:29 pm

Thanks for the suggestion both Christopher and Techman, having read of this fault several times on restoration threads over the years it still completely slipped my mind, it also sounds most likely as there are a few original capacitors still lurking about in the odd place. I'll take a look this afternoon and hopefully get the issue sorted.

Lloyd 1985 · 15th Jan 2023, 2:36 pm

The other possibility could be that something has become magnetised near the CRT, could even be the scan coils themselves. I had that on a Philips 385U where the scan coils have a big coil of steel wire wound over the top of them, I had to rewind that part as the original had rusted and sprung apart, I rather stupidly checked the new wire (welding wire!) was steel by sticking a big magnet to it… the resulting picture was offset quite a bit!

Regards,
Lloyd.

Freya · 15th Jan 2023, 2:44 pm

Also seen this can happen when tubes are re gunned and the gun assembly or neck is not centred correctly, this can be overcome by rotating the tube itself.

EF80TVVALVE · 15th Jan 2023, 6:25 pm

Thanks all for the suggestions. Should I be able to measure any DC at all on the scan coils of the D18T? I have heard of coils becoming magnetised before too, what is the best method to de-magnetise if this is the case?

I have checked over the circuit and most capacitors are new and good in that area. The only one I had any concerns of was C28A, the large metal cased 0.25uF which I have replaced although the original tested okay after removal.

Trying to adjust the picture to the centre does cause severe shadowing on the right side which is the side it should be over more, this makes me wonder if it is circuit related rather than anything around the neck of the CRT itself. As I previously said, adjusting the line hold brings it almost perfectly in with no shadowing but this is very close to where the picture loses sync. There is a 'nice' position further along where the picture locks neatly in place but too far over to the left of the screen.

EF80TVVALVE · 22nd Jan 2023, 6:18 pm

Hi all

Bit of a long reply on this one, I've got several projects taking up my attention aswell as trying to have a bit of a clear out! Here's an attached photo of the set with the horizontal hold slightly adjusted thus providing a nicely centred picture. This is close to the edge of losing sync and causes a tearing effect of the lines as can be seen.

Still haven't got much further as of yet but I can rule out any excessive current going to the coils via leaky caps but almost certain this is a scanning problem rather than the magnet assembly.

Cheers
Bren

Panrock · 22nd Jan 2023, 6:27 pm

I bet many of the original viewers never enjoyed a picture as good!

As a boy in the '50s, I remember being invited round to a neighbours for tea. From memory, their television picture had atrocious vertical non-linearity, and the brightness was too far advanced. This was accepted as 'normal'.

Steve

stevehertz · 22nd Jan 2023, 6:36 pm

Make sure there are no more wax or electrolytic caps hiding anywhere. If so just change them on sight!

EF80TVVALVE · 22nd Jan 2023, 7:12 pm

Steve (Panrock) I'm sure you're right, I'm sure with modern components plus converters these sets often display pictures better than they would have been capable of. I'm a bit of a perfectionist, I sometimes think we all can be a bit when restoring these sets. I would like to get it a bit better centred than it currently is, on the D18/B18 there is a nice part of the line hold control where the picture seats into a nice fixed position across a good part of the control, I think this part should also give a good centred picture, but it doesn't (as seen in post 4). I still have plenty to check so I'm not drawn to a dead end yet and I'm sure with some attention I will get it sorted.

Stevehertz, there's still a couple tucked away waiting for their superiors to turn up in the post. I don't think this will sort thd centring issue but it'll at least get rid of the hum bar on the picture which I'm certain is due to the smoothing can (also a nice hum on the audio).

12th Jan 2023, 8:17 pm	#1
EF80TVVALVE Octode Join Date: Feb 2010 Location: Leicester, UK. Posts: 1,433	Pye D18T. Hi all I picked up this D18T from Courtney Louise a few weeks ago, it's a welcome addition to the collection having had one many years ago that I had to pass on due to lack of space, one of the sets I wish I never had sold! It did have a fault with a lack of signal which I traced to a few wax capacitors hiding in the RF section. After these were replaced I finally had a picture. The contrast control on the front is very sharp and only works towards the upper end, turning back more than a quarter of the way causes loss of signal so I need to investigate further. Today a new problem developed. I'm attempting to get the picture centred better as it's a little too far over one side and the adjustments don't bring it in properly. Whilst adjusting the hardware around the neck the set suddenly lost all sync of the picture. The picture has lost frame hold just leaving a test card scrolling upwards, the line hold is also a bit unsteady but better than the frame hold. The picture also scrolls sideways on the screen. Oddly adjusting the volume control alters how much the picture collapses and rolls and there is an intermittent hum on the sound too. There are still a few original components in the set, I presume one of these has suddenly gave way causing the described fault. Just before I start poking around I just thought I'd ask any suggestions that may lead me in the right direction. Thanks all!

13th Jan 2023, 10:30 am	#2
mark pirate Dekatron Join Date: Mar 2008 Location: Worthing, West Sussex, UK Posts: 5,185	Re: Pye d18t I had similar problems when restoring my D18, at first I replaced the PZ30 & PL38, this improved matters, but changing the 100/60uF smoothing can fixed the problem. I had a similar contrast problem with my BV30, it was either on or off, changing the pot gave me more range & smooth operation. Mark

13th Jan 2023, 11:14 am	#3
EF80TVVALVE Octode Join Date: Feb 2010 Location: Leicester, UK. Posts: 1,433	Re: Pye d18t Thanks Mark, I managed to trace the fault to the 8uF 125v electrolytic (C17A) that had become a dead short, just by chance it happened whilst I was making adjustments. With this replaced I now have a picture again, still too far shifted over one side so I may look at the timebase components and make sure that everything is okay around there. There are some hum bars on the screen so I need to investigate this too, but it's nice to have a picture back on there!

14th Jan 2023, 10:30 pm	#4
EF80TVVALVE Octode Join Date: Feb 2010 Location: Leicester, UK. Posts: 1,433	Re: Pye d18t Some more fettling with the D18T today, I managed to spend some time removing the magnet assembly for the CRT. There are two rubber bumpers, basically some cut rubber hose that are used as a spring to keep the magnet up against the adjusting thumb nuts. These had deformed into their cramped up state so they were no longer providing that spring effect for the magnet. Some time in hot water and stretching them somewhat before re-fitting slightly rotated has returned a good amount of adjustment for the magnet. Whilst this is all good unfortunately it hasn't solved the problem with the shifted picture as I've attached a photo of. If I adjust the line hold control I can just about centre it before the image collapses so I'm going to look at this area of the circuit for any dodgy components. As can also be seen, there is some shadowing to one side of the picture which is down to the positioning of the rear magnet. Another thing I noticed is that the scan coils are way over one side and out of adjustment of the locking screw which has been removed in order to extend the range of the coil rotation and centre the picture. I wonder if the CRT fitted just isnt a very good match for this D18T, if that's even a possibility. I do have another set I can borrow the CRT from in order to see if this changes anything. For now I'm going to focus on getting the picture centred better and go from there. Attached Thumbnails

14th Jan 2023, 10:39 pm	#5
high_vacuum_house Octode Join Date: May 2003 Location: Belper Derbyshire Posts: 1,935	Re: Pye d18t With the picture offset to the left, I wander if you have some standing DC current flow through the line deflection coils causing this? Maybe a capacitor around the line output valve is leaking? Christopher Capener __________________ Interests in the collection and restoration of Tefifon players and 405 line television

15th Jan 2023, 1:13 am	#6
Techman Dekatron Join Date: Nov 2009 Location: Lincolnshire, UK. Posts: 5,000	Re: Pye d18t I agree that if it's not some sort of physical alignment type issue then it's likely to be a DC shift caused by leakage through a crucial capacitor.

15th Jan 2023, 2:29 pm	#7
EF80TVVALVE Octode Join Date: Feb 2010 Location: Leicester, UK. Posts: 1,433	Re: Pye d18t Thanks for the suggestion both Christopher and Techman, having read of this fault several times on restoration threads over the years it still completely slipped my mind, it also sounds most likely as there are a few original capacitors still lurking about in the odd place. I'll take a look this afternoon and hopefully get the issue sorted.

15th Jan 2023, 2:36 pm	#8
Lloyd 1985 Nonode Join Date: Jun 2008 Location: Coningsby, Lincolnshire, UK. Posts: 2,819	Re: Pye d18t The other possibility could be that something has become magnetised near the CRT, could even be the scan coils themselves. I had that on a Philips 385U where the scan coils have a big coil of steel wire wound over the top of them, I had to rewind that part as the original had rusted and sprung apart, I rather stupidly checked the new wire (welding wire!) was steel by sticking a big magnet to it… the resulting picture was offset quite a bit! Regards, Lloyd.

15th Jan 2023, 2:44 pm	#9
Freya Octode Join Date: Jan 2009 Location: Falmouth, Cornwall, UK. Posts: 1,990	Re: Pye d18t Also seen this can happen when tubes are re gunned and the gun assembly or neck is not centred correctly, this can be overcome by rotating the tube itself. __________________ Stephen _________"It`s only an old telly" ___ Last edited by Freya; 15th Jan 2023 at 2:50 pm.

15th Jan 2023, 6:25 pm	#10
EF80TVVALVE Octode Join Date: Feb 2010 Location: Leicester, UK. Posts: 1,433	Re: Pye d18t Thanks all for the suggestions. Should I be able to measure any DC at all on the scan coils of the D18T? I have heard of coils becoming magnetised before too, what is the best method to de-magnetise if this is the case? I have checked over the circuit and most capacitors are new and good in that area. The only one I had any concerns of was C28A, the large metal cased 0.25uF which I have replaced although the original tested okay after removal. Trying to adjust the picture to the centre does cause severe shadowing on the right side which is the side it should be over more, this makes me wonder if it is circuit related rather than anything around the neck of the CRT itself. As I previously said, adjusting the line hold brings it almost perfectly in with no shadowing but this is very close to where the picture loses sync. There is a 'nice' position further along where the picture locks neatly in place but too far over to the left of the screen.

22nd Jan 2023, 6:18 pm	#11
EF80TVVALVE Octode Join Date: Feb 2010 Location: Leicester, UK. Posts: 1,433	Re: Pye D18T. Hi all Bit of a long reply on this one, I've got several projects taking up my attention aswell as trying to have a bit of a clear out! Here's an attached photo of the set with the horizontal hold slightly adjusted thus providing a nicely centred picture. This is close to the edge of losing sync and causes a tearing effect of the lines as can be seen. Still haven't got much further as of yet but I can rule out any excessive current going to the coils via leaky caps but almost certain this is a scanning problem rather than the magnet assembly. Cheers Bren Attached Thumbnails

22nd Jan 2023, 6:27 pm	#12
Panrock Nonode Join Date: Feb 2005 Location: Worcestershire, UK. Posts: 2,533	Re: Pye D18T. I bet many of the original viewers never enjoyed a picture as good! As a boy in the '50s, I remember being invited round to a neighbours for tea. From memory, their television picture had atrocious vertical non-linearity, and the brightness was too far advanced. This was accepted as 'normal'. Steve

22nd Jan 2023, 6:36 pm	#13
stevehertz Dekatron Join Date: Sep 2011 Location: Rugeley, Staffordshire, UK. Posts: 8,831	Re: Pye D18T. Make sure there are no more wax or electrolytic caps hiding anywhere. If so just change them on sight! __________________ A digital radio is the latest thing, but a vintage wireless is forever..

22nd Jan 2023, 7:12 pm	#14
EF80TVVALVE Octode Join Date: Feb 2010 Location: Leicester, UK. Posts: 1,433	Re: Pye D18T. Steve (Panrock) I'm sure you're right, I'm sure with modern components plus converters these sets often display pictures better than they would have been capable of. I'm a bit of a perfectionist, I sometimes think we all can be a bit when restoring these sets. I would like to get it a bit better centred than it currently is, on the D18/B18 there is a nice part of the line hold control where the picture seats into a nice fixed position across a good part of the control, I think this part should also give a good centred picture, but it doesn't (as seen in post 4). I still have plenty to check so I'm not drawn to a dead end yet and I'm sure with some attention I will get it sorted. Stevehertz, there's still a couple tucked away waiting for their superiors to turn up in the post. I don't think this will sort thd centring issue but it'll at least get rid of the hum bar on the picture which I'm certain is due to the smoothing can (also a nice hum on the audio).