Bob Howe's 405 Line TV Thread. - UK Vintage Radio Repair and Restoration Discussion Forum

bobhowe · 9th Sep 2021, 6:34 pm

Hi i was at David Boynes shop yesterday and he was showing the TV he is working on & it is a Stella ST1011U what a well constructed & engineered set was this one one the easiest sets to work on ? kind regards Bob

bobhowe · 9th Sep 2021, 6:54 pm

Moderators please can you change title to What is the easiest 404 line tv to work on thanks

murphyv310 · 9th Sep 2021, 7:00 pm

Probably make it 405 Bob

Station X · 9th Sep 2021, 7:07 pm

The title was updated to avoid a proliferation of 405 line TV threads as we had with Bush DAC90/90A's.

bobhowe · 9th Sep 2021, 7:09 pm

Hi Trevor would be a rare set if it is 404 line

kind regards Bob

bobhowe · 9th Sep 2021, 7:12 pm

Quote:

Originally Posted by Station X

The title was updated to avoid a proliferation of 405 line TV threads as we had with Bush DAC90/90A's.

I undersand Graham kind regards Bob

Station X · 9th Sep 2021, 7:14 pm

Quote:

Originally Posted by bobhowe

Moderators please can you change title to What is the easiest 404 line tv to work on thanks

Quote:

Originally Posted by murphyv310

Probably make it 405 Bob

Quote:

Originally Posted by bobhowe

Hi Trevor would be a rare set if it is 404 line

kind regards Bob

Radio Wrangler · 9th Sep 2021, 7:36 pm

System A-1

David

Heatercathodeshort · 9th Sep 2021, 8:19 pm

Just twiddle the line hold a tiny fraction.

The Philips TG100U series [I think that is the Stella version David is working on] is certainly the easiest chassis to work on and saying that you very rarely have to work on it. Everything is accessible and removing the locking screw on the left latch allows you to remove the whole chassis in less than a minute.
I don't think I have ever cleaned the screen on one of this series and the Mullard AW43-88/ AW53-88 never fail and will probably carry on forever. Unfortunately the LOPTs after 60 odd years have become a problem. Note there are two different types that are not interchangeable. John.
Later Philips models had swing out panels rather than the whole chassis. Some of the most reliable receivers ever produced at Commerce Way Croydon.
PS How did they get that contrast range and video drive from an EF80! I don't think Philips used the PCL84 in any of their receivers. The later models reverted to the old 1950 World series PL83 as video output.

FERNSEH · 9th Sep 2021, 10:14 pm

The Stella version of the Philips 21TG100U is the ST1011U, electrically identical differing only in cabinet presentation.
The line output transformer in the Stella set I'm working on was found to be faulty and the grand plan was to fit the later Philips "Style70" line output transformer.
In many respects the later transformer is similar to the transformer in the ST1011. The replacement transformer was donated by the owner of the Stella.
The Style70 LOPTx was subjected to the warming up procedure by passing a small current through the EHT and primary windings, transformer left in this condition over five days.
The "new" transformer was wired into the circuit, final checks to confirm everything was in order before switching on.
But it was bad news, the replacement transformer lasted only one minute, the insulation between two separate windings in the transformer broke down. So now the plan is fit a Thorn jellypot transformer. That job is now well underway so we'll know the results by the weekend.
The circuit of modified line output stage will resemble the early production versions of these receivers. The attachment shows the early line timbase circuit.
Nevertheless, the Stella ST1011 and the Philips 21TG100U were among the very best 405 line TV receivers on sale in 1960.
Easy to service and at the time excellent back-up service from the manufactures' service department.

DFWB.

murphyv310 · 10th Sep 2021, 8:07 am

Hi.
These Philips transformers certainly haven't bode well after years of having a rest. In fairness they were not that reliable even during the sets normal service life.
Youll never kill a jellypot unless the tags get damaged the only real weak point on them.

Panrock · 10th Sep 2021, 9:21 am

Here's my 17TG100U.

It's now on its third LOPT. Another weak spot is the sound quality, which tends to be thin. But with the sharp, bright picture and the easy servicing this is easy to forgive.

Steve

Heatercathodeshort · 10th Sep 2021, 10:10 am

This chassis is unusual in obtaining the anode voltage for the sound pre-amp section of the PCL83 from the boost rail via a 2.7M resistor. It forms a noise limiter circuit and when the resistor goes high as it always does, the sound at first becomes distorted, then fails altogether.
Another very common fault with early versions using potted scan coils was failure of the frame section of the coils giving a frame collapse with the classic wavy line. The replacement coils supplied by Philips were of the conventional open type.

That is a nice example Steve. The early version of the LOPT in a 21TG100U has just failed at the Dulwich Museum! We are not alone. John.

bobhowe · 10th Sep 2021, 11:33 am

Hi why is the LOPT so unreliable.? its a shame for s well built set kind regards Bob

dazzlevision · 10th Sep 2021, 12:02 pm

Maybe because the windings are not encapsulated in either wax or pitch - or a design fault, with inadequate insulation between windings.

9th Sep 2021, 6:34 pm	#1
bobhowe Heptode Join Date: Jun 2005 Location: Sunderland, Tyne and Wear, UK. Posts: 661	Bob Howe's 405 Line TV Thread. Hi i was at David Boynes shop yesterday and he was showing the TV he is working on & it is a Stella ST1011U what a well constructed & engineered set was this one one the easiest sets to work on ? kind regards Bob

9th Sep 2021, 6:54 pm	#2
bobhowe Heptode Join Date: Jun 2005 Location: Sunderland, Tyne and Wear, UK. Posts: 661	Re: Bob Howe's 405 Line TV Thread. Moderators please can you change title to What is the easiest 404 line tv to work on thanks

9th Sep 2021, 7:00 pm	#3
murphyv310 Dekatron Join Date: Sep 2006 Location: Kilmarnock, Ayrshire, UK. Posts: 5,422	Re: Bob Howe's 405 Line TV Thread. Probably make it 405 Bob __________________ Cheers, Trevor. MM0KJJ. RSGB, GQRP, WACRAL, K&LARC. Member

9th Sep 2021, 7:07 pm	#4
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,288	Re: Bob Howe's 405 Line TV Thread. The title was updated to avoid a proliferation of 405 line TV threads as we had with Bush DAC90/90A's. __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

9th Sep 2021, 7:09 pm	#5
bobhowe Heptode Join Date: Jun 2005 Location: Sunderland, Tyne and Wear, UK. Posts: 661	Re: Bob Howe's 405 Line TV Thread. Hi Trevor would be a rare set if it is 404 line kind regards Bob

9th Sep 2021, 7:36 pm	#8
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,869	Re: Bob Howe's 405 Line TV Thread. System A-1 David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

9th Sep 2021, 8:19 pm	#9
Heatercathodeshort Dekatron Join Date: Jun 2005 Location: Warnham, West Sussex. 10 miles south of DORKING. Posts: 9,147	Re: Bob Howe's 405 Line TV Thread. Just twiddle the line hold a tiny fraction. The Philips TG100U series [I think that is the Stella version David is working on] is certainly the easiest chassis to work on and saying that you very rarely have to work on it. Everything is accessible and removing the locking screw on the left latch allows you to remove the whole chassis in less than a minute. I don't think I have ever cleaned the screen on one of this series and the Mullard AW43-88/ AW53-88 never fail and will probably carry on forever. Unfortunately the LOPTs after 60 odd years have become a problem. Note there are two different types that are not interchangeable. John. Later Philips models had swing out panels rather than the whole chassis. Some of the most reliable receivers ever produced at Commerce Way Croydon. PS How did they get that contrast range and video drive from an EF80! I don't think Philips used the PCL84 in any of their receivers. The later models reverted to the old 1950 World series PL83 as video output.

9th Sep 2021, 10:14 pm	#10
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: Bob Howe's 405 Line TV Thread. The Stella version of the Philips 21TG100U is the ST1011U, electrically identical differing only in cabinet presentation. The line output transformer in the Stella set I'm working on was found to be faulty and the grand plan was to fit the later Philips "Style70" line output transformer. In many respects the later transformer is similar to the transformer in the ST1011. The replacement transformer was donated by the owner of the Stella. The Style70 LOPTx was subjected to the warming up procedure by passing a small current through the EHT and primary windings, transformer left in this condition over five days. The "new" transformer was wired into the circuit, final checks to confirm everything was in order before switching on. But it was bad news, the replacement transformer lasted only one minute, the insulation between two separate windings in the transformer broke down. So now the plan is fit a Thorn jellypot transformer. That job is now well underway so we'll know the results by the weekend. The circuit of modified line output stage will resemble the early production versions of these receivers. The attachment shows the early line timbase circuit. Nevertheless, the Stella ST1011 and the Philips 21TG100U were among the very best 405 line TV receivers on sale in 1960. Easy to service and at the time excellent back-up service from the manufactures' service department. DFWB. Attached Thumbnails

10th Sep 2021, 8:07 am	#11
murphyv310 Dekatron Join Date: Sep 2006 Location: Kilmarnock, Ayrshire, UK. Posts: 5,422	Re: Bob Howe's 405 Line TV Thread. Hi. These Philips transformers certainly haven't bode well after years of having a rest. In fairness they were not that reliable even during the sets normal service life. Youll never kill a jellypot unless the tags get damaged the only real weak point on them. __________________ Cheers, Trevor. MM0KJJ. RSGB, GQRP, WACRAL, K&LARC. Member

10th Sep 2021, 9:21 am	#12
Panrock Nonode Join Date: Feb 2005 Location: Worcestershire, UK. Posts: 2,533	Re: Bob Howe's 405 Line TV Thread. Here's my 17TG100U. It's now on its third LOPT. Another weak spot is the sound quality, which tends to be thin. But with the sharp, bright picture and the easy servicing this is easy to forgive. Steve Attached Thumbnails __________________ https://www.radiocraft.co.uk

10th Sep 2021, 10:10 am	#13
Heatercathodeshort Dekatron Join Date: Jun 2005 Location: Warnham, West Sussex. 10 miles south of DORKING. Posts: 9,147	Re: Bob Howe's 405 Line TV Thread. This chassis is unusual in obtaining the anode voltage for the sound pre-amp section of the PCL83 from the boost rail via a 2.7M resistor. It forms a noise limiter circuit and when the resistor goes high as it always does, the sound at first becomes distorted, then fails altogether. Another very common fault with early versions using potted scan coils was failure of the frame section of the coils giving a frame collapse with the classic wavy line. The replacement coils supplied by Philips were of the conventional open type. That is a nice example Steve. The early version of the LOPT in a 21TG100U has just failed at the Dulwich Museum! We are not alone. John.

10th Sep 2021, 11:33 am	#14
bobhowe Heptode Join Date: Jun 2005 Location: Sunderland, Tyne and Wear, UK. Posts: 661	Re: Bob Howe's 405 Line TV Thread. Hi why is the LOPT so unreliable.? its a shame for s well built set kind regards Bob

10th Sep 2021, 12:02 pm	#15
dazzlevision Dekatron Join Date: Sep 2003 Location: Near Swindon, North Wiltshire, UK. Posts: 3,611	Re: Bob Howe's 405 Line TV Thread. Maybe because the windings are not encapsulated in either wax or pitch - or a design fault, with inadequate insulation between windings.