UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio and TV Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Specific Vintage Equipment > Vintage Television and Video

Notices

Vintage Television and Video Vintage television and video equipment, programmes, VCRs etc.

Reply
 
Thread Tools
Old 27th Feb 2020, 11:00 pm   #321
System A
Pentode
 
System A's Avatar
 
Join Date: Feb 2006
Location: County Durham, UK.
Posts: 225
Default Re: Baird T5 restoration project.

Hi David, what a superb job you're making of this restoration.
I'm throughly enjoying this thread.
Regards.
Gary
System A is offline   Reply With Quote
Old 28th Feb 2020, 11:39 am   #322
mark pirate
Dekatron
 
mark pirate's Avatar
 
Join Date: Mar 2008
Location: Worthing, West Sussex, UK
Posts: 4,954
Default Re: Baird T5 restoration project.

I am in awe at your cabinet skills David, Looking forward to see the finish go on!

Mark
mark pirate is offline   Reply With Quote
Old 28th Feb 2020, 12:55 pm   #323
stevehertz
Dekatron
 
stevehertz's Avatar
 
Join Date: Sep 2011
Location: Rugeley, Staffordshire, UK.
Posts: 5,059
Default Re: Baird T5 restoration project.

This is a critical stage now as all that excellent woodwork needs to be topped with appropriate coloured lacquers and/or the use of stains beforehand. I once completely stripped a small Marconi radiogram. Once stripped, the various wood panels and edhe mouldings were different coloured woods. It was a hell of a game trying to get finishes to match up. I didn't quite achieve it! Best of luck David, I'm sure you're going to amaze us again.
__________________
A digital radio is the latest thing, but a vintage wireless is forever..
stevehertz is online now   Reply With Quote
Old 28th Feb 2020, 2:13 pm   #324
Panrock
Nonode
 
Panrock's Avatar
 
Join Date: Feb 2005
Location: Worcestershire, UK.
Posts: 2,033
Default Re: Baird T5 restoration project.

First, a big (and humble) "well done" for what David (DFWB) has achieved here. Not many would have taken this job on. Still fewer managed to obtain such a good result.

There are probably as many opinions on the subject of finishing as there are people here. As I've said before, I personally am opposed to the use of stains for tinting purposes. By the thirties and forties, coloured toning lacquers were the order of the day for the mass marketed radio industry, and using these again will be good for originality. Moreover, when using a spray gun, their density can be controlled by mixing with the filler/base coat. One advantage here is that you gain more grain pit filling, and another from using toner is that the colours of adjacent (different) sprayed panels will tend to converge.

I think David said he is going the French Polish route here, however. I'm sure the final result will be most impressive.

Steve
Panrock is online now   Reply With Quote
Old 28th Feb 2020, 4:21 pm   #325
FERNSEH
Dekatron
 
FERNSEH's Avatar
 
Join Date: Mar 2005
Location: Gateshead, Tyne and Wear, UK.
Posts: 6,435
Default Re: Baird T5 restoration project.

Panrock wrote:
"There are probably as many opinions on the subject of finishing as there are people here. As I've said before, I personally am opposed to the use of stains for tinting purposes. By the thirties and forties, coloured toning lacquers were the order of the day for the mass marketed radio industry, and using these again will be good for originality. Moreover, when using a spray gun, their density can be controlled by mixing with the filler/base coat. One advantage here is that you gain more grain pit filling, and another from using toner is that the colours of adjacent (different) sprayed panels will tend to converge."

I think David said he is going the French Polish route here, however. I'm sure the final result will be most impressive.


Hi Steve,

rather than French polishing the completed cabinet I'm considering passing the final finishing to a local firm to have it spray painted just as it was done in 1937 when the set was made. A very dark lacquer was used for the original finish, the norm for those times. It's something to be discussed with the owner of the set.

DFWB.
FERNSEH is online now   Reply With Quote
Old 28th Feb 2020, 4:31 pm   #326
FERNSEH
Dekatron
 
FERNSEH's Avatar
 
Join Date: Mar 2005
Location: Gateshead, Tyne and Wear, UK.
Posts: 6,435
Default Re: Baird T5 restoration project.

Quote:
Originally Posted by stevehertz View Post
This is a critical stage now as all that excellent woodwork needs to be topped with appropriate coloured lacquers and/or the use of stains beforehand. I once completely stripped a small Marconi radiogram. Once stripped, the various wood panels and edhe mouldings were different coloured woods. It was a hell of a game trying to get finishes to match up. I didn't quite achieve it! Best of luck David, I'm sure you're going to amaze us again.
Hi Steve,
on the previous page the picture of the almost completed cabinet clearly shows the different coloured woods used during the assembly. That's why I'm sure all those mass produced radios were always in a dark finish. Helps to hide some of the imperfections as well. How often have you seen that after stripping off the lacquered surfaces off old radios?

DFWB.

Last edited by FERNSEH; 28th Feb 2020 at 4:52 pm.
FERNSEH is online now   Reply With Quote
Old 28th Feb 2020, 9:53 pm   #327
Magpie66
Diode
 
Join Date: Jul 2018
Location: Chesham, Buckinghamshire, UK.
Posts: 6
Default Re: Baird T5 restoration project.

When we rescued this T5 it was full of woodworm and dust and was only held together by the veneer and varnish. Now look at it. A piece of history brought back to life. After we acquired this Television we were unsure what to do with it as it was in such a bad condition but thanks to feedback from various members on this forum we decided to have it renovated and so many people recommended David.
You have done a grand job and I donít think we could have chosen a better person to complete the work.
Keep it up.
Ant and Tina
Magpie66 is offline   Reply With Quote
Old 29th Feb 2020, 12:00 pm   #328
stevehertz
Dekatron
 
stevehertz's Avatar
 
Join Date: Sep 2011
Location: Rugeley, Staffordshire, UK.
Posts: 5,059
Default Re: Baird T5 restoration project.

Quote:
Originally Posted by FERNSEH View Post
Panrock wrote:
"There are probably as many opinions on the subject of finishing as there are people here. As I've said before, I personally am opposed to the use of stains for tinting purposes. By the thirties and forties, coloured toning lacquers were the order of the day for the mass marketed radio industry, and using these again will be good for originality. Moreover, when using a spray gun, their density can be controlled by mixing with the filler/base coat. One advantage here is that you gain more grain pit filling, and another from using toner is that the colours of adjacent (different) sprayed panels will tend to converge."
I think David said he is going the French Polish route here, however. I'm sure the final result will be most impressive.

Hi Steve,
rather than French polishing the completed cabinet I'm considering passing the final finishing to a local firm to have it spray painted just as it was done in 1937 when the set was made. A very dark lacquer was used for the original finish, the norm for those times.
It's something to be discussed with the owner of the set.

DFWB.
Definitely the way to go. Nonetheless, a lacquer - even a dark one - can only 'equalise' the colour of woods underneath to some extent. Personally I would consider using stains on the bare wood to 'help' the process prior to spraying, and that would also mean that you would not have to use such a dark lacquer. As I recall, the T5 was not finished in a dark colour, more of a medium brown.

The original lacquer would have been cellulose. Not sure if you're able to get someone to use that, but that's what it was.
__________________
A digital radio is the latest thing, but a vintage wireless is forever..
stevehertz is online now   Reply With Quote
Old 3rd Feb 2021, 6:36 pm   #329
FERNSEH
Dekatron
 
FERNSEH's Avatar
 
Join Date: Mar 2005
Location: Gateshead, Tyne and Wear, UK.
Posts: 6,435
Default Baird T5 restoration project.

It's almost a year since I posted up anything about this set.

https://www.vintage-radio.net/forum/...152005&page=17

Work on the set continues.
The cabinet is ready for the final finish to be applied to the surfaces.
However, the plan was to use the original CRT mounting board, but now I'm having second thoughts about using it and the replica board is to be fitted instead. The CRT bulb sits on this board and the hole has to be chamfered to the correct angle to accommodate the shape of the tube. A special router tool was bought for this purpose. A piece of 9mm plywood with a 7 inch diameter hole cut out in it was to used so that the wheel on the router tool can be guided just away from the edge of the hole in the CRT board.
That job has been done and now I've turned my attention to the replica focus coil mounting board. Again the same router tool was used to make the chamfered edge in the four inch hole for the focus coil plate.

DFWB.
Attached Thumbnails
Click image for larger version

Name:	Baird_T5_CRT_Board.jpg
Views:	193
Size:	102.8 KB
ID:	225903   Click image for larger version

Name:	Baird_T5_Focus_Coil_Board.jpg
Views:	176
Size:	62.7 KB
ID:	225904  
FERNSEH is online now   Reply With Quote
Old 5th Feb 2021, 8:06 pm   #330
FERNSEH
Dekatron
 
FERNSEH's Avatar
 
Join Date: Mar 2005
Location: Gateshead, Tyne and Wear, UK.
Posts: 6,435
Default Re: Baird T5 restoration project.

It's getting close to the stage where a CRT must be fitted in the cabinet to confirm that all the new parts are in the correct positions. But it would be certainly unwise to use the original tube for the purpose. Once that component has been installed it stays in unless other reasons arise. With TV sets having a 12" diameter tube I have a down-to-air CRM121 which is used to determine the installation arrangements before a good tube is fitted. An example is my Beau Decca TV recreation.

The Cathodevisor CRT has a 41mm neck diameter. A wound steel tube is fitted over the CRT neck, the line scanning coils are fitted close to the flare of the bulb and the frame scanning coils are mounted on the CRT mounting board.

The dummy tube won't be a CRT but a length of tubing attached to a wood disc which will be placed in the position where tube bulb rests on the upper board. The attached picture shows a piece of plumbers pipe which is almost the same diameter as the CRT neck.

DFWB.
Attached Thumbnails
Click image for larger version

Name:	Baird_T5_CRT_Sub..jpg
Views:	126
Size:	48.8 KB
ID:	226039  
FERNSEH is online now   Reply With Quote
Old 8th Feb 2021, 10:05 pm   #331
FERNSEH
Dekatron
 
FERNSEH's Avatar
 
Join Date: Mar 2005
Location: Gateshead, Tyne and Wear, UK.
Posts: 6,435
Default Re: Baird T5 restoration project.

The 15MW4 CRT is a post-war replacement. Certain modifications were required to install the tube including an octagonal shaped wood adaptor block to move the position of the focus coil.

The pre-war tube was the Cathodevisor 15MW1 or 15MW2. A 15MW3 was made but this was a post-war tube which was similar to the Mazda CRM151.

DFWB.
Attached Thumbnails
Click image for larger version

Name:	BairdT5_Televisor_15MW4_2-3.jpg
Views:	79
Size:	113.6 KB
ID:	226331  
FERNSEH is online now   Reply With Quote
Old 9th Feb 2021, 6:15 pm   #332
beery
Heptode
 
beery's Avatar
 
Join Date: Jun 2006
Location: Ware, Hertfordshire, UK.
Posts: 837
Default Re: Baird T5 restoration project.

Hi David,
That's great.
I've now received the mouse eaten line output transformer.
I will be attempting a simple repair of the outer layer rather than full rewinding.
First of all I need to remove the lamminations, which shouldn't be too hard because these transformers were never varnished.

I will report back on my progress at this end.

Cheers
Andy
Attached Thumbnails
Click image for larger version

Name:	IMG_20210209_151015s.jpg
Views:	100
Size:	97.7 KB
ID:	226388  
beery is online now   Reply With Quote
Old 19th Feb 2021, 10:13 am   #333
beery
Heptode
 
beery's Avatar
 
Join Date: Jun 2006
Location: Ware, Hertfordshire, UK.
Posts: 837
Default Re: Baird T5 restoration project.

Hi all,
I've now repaired the Baird T5 line output transformer.

The outer (synch injection) winding had been chewed by some wee beastie.

I took off the laminations to get to the windings. The laminations are T and U stampings, which were alternatively arranged as in a mains transformer, this is unusual in a line output transformer where we would expect the laminations grouped together and gapped.
The outer layer consisted of 10 turns of 36SWG (0.19mm) SSC (Single Silk Covered wire) which was no enamelled. A few of those turns were broken in the same place.
I unwound the damaged layer and found 33 healthy turns. 3 turns from this layer were unwound to provide a good lead in to a wire splice. I then covered the good layer back up with craft tape, cut back the wire to about 1 turn and spliced on some new 36SWG enamelled wire. I then added another 12 turns to get back to where we were before. As it was the final layer, there was space to spread the wire out a bit, which would give more even support to the lead out terminal.
Some transformer tape was used to stabilise the windings, but I was careful not to let it go too near the edges of the craft paper. So that the bright yellow tape would be hidden when the repair was completed.
A layer of craft tape was added and the terminal was connected and secured with fibre glass tape. More craft tape was added over the top.
Finally about half of the original varnished cloth outer insulation was glued back on. The damaged insulation on the top part of the transformer was replaced by similar material that was recovered from a scrap GPO 3000 type relay.
I will post the transformer back to David next week.

Some observations on the transformer design:-
Very unusually proportioned laminations made for a narrow, but thick coil, i.e. many layers, each with a small number of turns - this makes for a transformer with low inter-turn capacitance, great for responding to the rapid flyback of the line scan. Single Silk Covered wire has a slightly larger overall diameter than enamelled copper wire and this will have assisted in reducing the winding capacitance. For VHF coils often Double Silk Covered wire was used in pre-war sets.
Anyway, the use of a narrow but tall winding Single Silk Covered wire can be considered an alternative to wave winding a line output transformer. As I had only to replace 12 turns on the outer layer then enamelled copper wire slightly spaced out will be fine. If I had to rewind the whole thing then another approach would have to be considered. Synthetic silk covered wire is available, but it is very very expensive.

Cheers
Andy
Attached Thumbnails
Click image for larger version

Name:	IMG_20210212_115306s.jpg
Views:	104
Size:	103.5 KB
ID:	227070   Click image for larger version

Name:	IMG_20210212_135856s.jpg
Views:	98
Size:	108.3 KB
ID:	227071   Click image for larger version

Name:	IMG_20210212_143131s.jpg
Views:	98
Size:	95.9 KB
ID:	227072   Click image for larger version

Name:	IMG_20210215_193751s.jpg
Views:	102
Size:	100.1 KB
ID:	227073  
beery is online now   Reply With Quote
Old 20th Feb 2021, 8:55 am   #334
peter_scott
Nonode
 
peter_scott's Avatar
 
Join Date: May 2003
Location: Edinburgh, UK.
Posts: 2,686
Default Re: Baird T5 restoration project.

A really beautiful repair.

Well done!

Interesting construction too.

Peter
peter_scott is online now   Reply With Quote
Old 20th Feb 2021, 8:59 am   #335
ChristianFletcher
Heptode
 
ChristianFletcher's Avatar
 
Join Date: Dec 2003
Location: South Yorkshire, UK.
Posts: 565
Default Re: Baird T5 restoration project.

Yes I agree that transformer repair is very impressive
__________________
Every Silver Lining Has Its Cloud !
ChristianFletcher is offline   Reply With Quote
Old 20th Feb 2021, 4:29 pm   #336
FERNSEH
Dekatron
 
FERNSEH's Avatar
 
Join Date: Mar 2005
Location: Gateshead, Tyne and Wear, UK.
Posts: 6,435
Default Re: Baird T5 restoration project.

Hi Andy,
many thanks for doing a superb job, it looks great. As soon as it arrives I'll set about restoring the timebase unit. It's the only unit that hasn't been been fully checked over. The T23 can be employed as the test receiver, assuming of course the CRT can be made to work again.
The attachment shows the circuit diagram of the self-oscillating line timebase.
The line scanning coils are fitted on the CRT neck in the usual manner and the frame timebase employs that clever arrangement in which the oscillator transformer has those laminations which extend out to the neck of the CRT.

DFWB.
Attached Thumbnails
Click image for larger version

Name:	BairdT5LTB_cct_2.jpg
Views:	28
Size:	34.2 KB
ID:	227217  
FERNSEH is online now   Reply With Quote
Old 20th Feb 2021, 5:40 pm   #337
beery
Heptode
 
beery's Avatar
 
Join Date: Jun 2006
Location: Ware, Hertfordshire, UK.
Posts: 837
Default Re: Baird T5 restoration project.

Hi David,
can you measure the scan coil resistances for completeness? It would be interesting to compare them with my Garrick which is a development of the T18.

I've measured the resistances and inductances of the windings on the T5 line output transformer. They are:-
1st winding, Brown leads, 322ohms, 2.5H
2nd Winding, Brown leads, 59 ohms, 635mH
3rd winding, Yellow leads, 55 ohms, 406mH

The leads for the start of each winding emerge from the top of the transformer and the leads for the end of eacj winding emerge from the bottom of the transformer. As the transformer is mounted on its side in a drop-through style then it really does not matter which way round it goes. Well it does now of course because the wires having been cut to length when the set was made will now only fit one way! Anyway, the idea of having all windings start on one side and finish on the other is very clever in its simplicity and also fool proof.

Cheers
Andy
Attached Thumbnails
Click image for larger version

Name:	IMG_20210215_193807s.jpg
Views:	30
Size:	117.1 KB
ID:	227222  

Last edited by beery; 20th Feb 2021 at 5:43 pm. Reason: Typo in inductance figures
beery is online now   Reply With Quote
Old 20th Feb 2021, 7:27 pm   #338
FERNSEH
Dekatron
 
FERNSEH's Avatar
 
Join Date: Mar 2005
Location: Gateshead, Tyne and Wear, UK.
Posts: 6,435
Default Re: Baird T5 restoration project.

Hi Andy,
I've checked the DC resistances of the line scanning coils in the T5 and T23, both read 29ohms.
There is a 50mfd DC blocking capacitor in series with the scanning coils. It is safe to suggest the waveform at the grid of the 41MP triode is negative going as one would expect in an oscillator, the presence of the series capacitor will supply the coils with a sawtooth waveform symmetrical about zero.
All the Cossor 41MP triodes I've come across in Baird TV receivers are triode connected tetrodes or pentodes. Very early 41MP valves were true triodes.
High peak voltages are present at the anode of the line output valve, hence the ceramic valveholder.
Some info about the Cossor 41MP: https://www.radiomuseum.org/tubes/tube_41mp.html

DFWB.
FERNSEH is online now   Reply With Quote
Reply

Thread Tools



All times are GMT. The time now is 6:39 pm.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2021, vBulletin Solutions, Inc.
Copyright ©2002 - 2021, Paul Stenning.