Baird T5 restoration project. - Page 7 - UK Vintage Radio Repair and Restoration Discussion Forum

1100 man · 13th Feb 2019, 10:54 pm

Hi David,
I've been following your progress with this restoration with great interest! At least with the cabinet in that bad a state, the decision to replace most parts of it is made rather easier.
It must have been a very satisfying project so far. Of course, when you come to the veneering, things will get even more difficult! Have you much experience of doing this?
Well done on progress so far.

All the best
Nick

FERNSEH · 14th Feb 2019, 11:35 am

Hi Nick,
fortunately there is not too much veneering work required for this job.
The CRT screen panel, the new control panel and the front panel will need veneering. The side panels are furniture grade plywood and have very nice wood grain patterns. The new panels can be stained and polished before final assembly. The mirror lid is in good condition and requires little attention other than stripping off the old lacquer and a few minor repairs to the veneers.

The screen aperture has a 30 degree chamfer around the edges. That part of the job went well, see second picture. However, things didn't go well when it came to routing out the 5mm recess for the implosion glass. The router tool kinda went wild and ruined the panel. So that panel will join the woodworm damaged parts. Scrap!

DFWB.

FERNSEH · 18th Feb 2019, 11:09 am

It will be possible to repair the damaged CRT display panel but instead I will make a new one which will be constructed from two pieces of 6mm plywood glued together.
I'm now on the lookout for veneer for the front panels.

DFWB.

Hunts smoothing bomb · 18th Feb 2019, 10:42 pm

Great progress David, the skills that you possess in cabinetry I find nothing short of amazing!

This is going to be a super set when finished.

Cheers

FERNSEH · 20th Feb 2019, 12:20 pm

Hi Lee,
The cabinet reconstruction is progressing very well. The control panel is the last cabinet part to be made. I'll attempt to do this later this week. In the meantime let's take a look at the vision receiver. Signals are supplied direct to the mixer, no RF amplifier. This was a common practise in early TV receivers. Because the intermediate frequency is low the four stage amplifier should provide excellent gain. The Mullard TSP4 pentodes have a gm of 4.2ma/V which is a good figure for early television RF pentodes. Because the set employs a large CRT a full wave demodulator is employed in order to avoid a fine dot pattern appearing on the screen. A Mullard 2D4A double-diode is used as the vision detector. A TSP4 is used as the video amplifier.
Positive going video is supplied to the CRT grid via a capacitor. No DC restorer.

DFWB.

ThePillenwerfer · 27th Feb 2019, 12:31 am

Come on, David, let's have an up-date. The suspense is killing me: have the woodworm eaten you?

FERNSEH · 27th Feb 2019, 11:02 am

"have the woodworm eaten you?" Hi Pillenwerfer,
But they have made a good meal of every plywood panel. The control panel is the last cabinet part to be made and it is proving to be a bit difficult replicate but I will have something show on the forum by the weekend.
The vision receiver and the power supply units are on the bench for servicing. We'll soon find out the intermediate frequency and the passband characteristics of the IF amplifier.

DFWB.

FERNSEH · 27th Feb 2019, 5:56 pm

Testing the power supply unit. The 16mfd reservoir capacitor and the 24mfd main smoothing capacitor were found to be useless so for the time being two 8 + 8 mfd capacitors will be used until the correct components can be found.

Under no load and with only 150VAC supplied from the variac the smoothed HT voltage is 300V. Later today the vision and sound receivers will be connected to the power supply.

DFWB.

ThePillenwerfer · 27th Feb 2019, 7:03 pm

Good to hear that your steadily progressing.

FERNSEH · 28th Feb 2019, 11:28 am

In fact as the picture shows I've little choice but to make a new control panel.

DFWB.

ekjdm14 · 28th Feb 2019, 11:48 am

Wow, only just seen this thread & the first thing that springs to mind is that episode of The Young Ones... "Vivien, eat the telly!"

Right, now I've got that off my chest I shall go back and continue reading. It looks like one heck of a project and I doff my hat to you for taking it on.

beery · 1st Mar 2019, 3:09 am

Hi David,
I'm loving the progress by the way.
I've uploaded a photo of how the vision unit would have looked with the original capacitors. The electrolytics in the one you are restoring have been very neatly fitted, so I would say definitely a manufacturer's post war overhaul.

Another thing I have noticed by looking at photos of other surviving T5 sets is that sometimes the speaker is on the other side of the cabinet. I can't see any reason why moving it to the other side would help really, so maybe it is just random...

Cheers
Andy

FERNSEH · 1st Mar 2019, 12:47 pm

Today's report is about the good progress I'm making with the sound and vision receiver units. The oscilloscope trace shows the negative going video present at the grid of the TSP4 video output valve. Despite having no RF amplifier the vision receiver has high gain. It has been established that the vision IF amplifier is aligned to the upper sideband which means there is a deep "trough" between the vision and sound passbands. The vision IF is 13mc/s, much higher than I thought it would have been.
Much more work needs to be done on the vision receiver but the results so far are very encouraging.

DFWB.

FERNSEH · 2nd Mar 2019, 5:21 pm

Today the new control panel was test fitted.

The panel is canted back 35 degrees which made it necessary to adjust the angle of the cutting disc on that scary saw bench.

DFWB.

Magpie66 · 7th Mar 2019, 9:21 pm

Hi Dave.

Got one of those saws myself,not my favourite tool.

Nice to see your progress on the T5. I remember you saying that you were enjoying this restoration. Hope the problems you have encountered haven’t changed your mind.

Keep up the good work, Anthony.

FERNSEH · 7th Mar 2019, 11:24 pm

Hi Anthony,
The restoration of the Baird T5 is progressing well. Just two more jobs to do before the wood veneers are applied to the surfaces of the cabinet front panel, the control panel and the CRT screen panel.
First task to do this weekend is make the specially shaped beading fitted between the control panel and the upper panel, see the attached pictures. It might be possible to use ordinary stock beading available from B & Q. Again, the saw bench will cut out the 30 degree chamfer.

The second task is to make the cut out in the front panel for the door to access the timebase controls.

DFWB.

FERNSEH · 14th Mar 2019, 10:20 pm

The cut out in the front panel for the timebase controls door was made today.
The front panel is now ready for the surface veneers to be applied.

DFWB.

beery · 15th Mar 2019, 2:26 am

I see you have included a cat sized fire escape via the speaker aperture...

FERNSEH · 27th Mar 2019, 1:40 pm

All the interior surfaces of the cabinet are matt black and of course the best paint for the job is that used for blackboards.

DFWB.

FERNSEH · 2nd Apr 2019, 3:37 pm

Decisions, Decisions. The attachment shows two CRT support panels, the one on the left is the original and the other is the newly made replica.
The CRT panel was the only plywood part in the set that wasn't totally destroyed by woodworm, only one corner of the panel had been invaded by the worms.
So, the question is, in order to maintain some originality should the refurbished panel be used in the reconstruction or, should we play safe and fit the replica part?

DFWB.

13th Feb 2019, 10:54 pm	#121
1100 man Octode Join Date: Apr 2016 Location: Ventnor, Isle of Wight, & Great Dunmow, Essex, UK. Posts: 1,377	Re: Baird T5 restoration project. Hi David, I've been following your progress with this restoration with great interest! At least with the cabinet in that bad a state, the decision to replace most parts of it is made rather easier. It must have been a very satisfying project so far. Of course, when you come to the veneering, things will get even more difficult! Have you much experience of doing this? Well done on progress so far. All the best Nick

14th Feb 2019, 11:35 am	#122
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,375	Re: Baird T5 restoration project. Hi Nick, fortunately there is not too much veneering work required for this job. The CRT screen panel, the new control panel and the front panel will need veneering. The side panels are furniture grade plywood and have very nice wood grain patterns. The new panels can be stained and polished before final assembly. The mirror lid is in good condition and requires little attention other than stripping off the old lacquer and a few minor repairs to the veneers. The screen aperture has a 30 degree chamfer around the edges. That part of the job went well, see second picture. However, things didn't go well when it came to routing out the 5mm recess for the implosion glass. The router tool kinda went wild and ruined the panel. So that panel will join the woodworm damaged parts. Scrap! DFWB. Attached Thumbnails

18th Feb 2019, 11:09 am	#123
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,375	Re: Baird T5 restoration project. It will be possible to repair the damaged CRT display panel but instead I will make a new one which will be constructed from two pieces of 6mm plywood glued together. I'm now on the lookout for veneer for the front panels. DFWB.

18th Feb 2019, 10:42 pm	#124
Hunts smoothing bomb Octode Join Date: Oct 2005 Location: Wimborne, Dorset, UK. Posts: 1,406	Re: Baird T5 restoration project. Great progress David, the skills that you possess in cabinetry I find nothing short of amazing! This is going to be a super set when finished. Cheers __________________ Lee

20th Feb 2019, 12:20 pm	#125
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,375	Re: Baird T5 restoration project. Hi Lee, The cabinet reconstruction is progressing very well. The control panel is the last cabinet part to be made. I'll attempt to do this later this week. In the meantime let's take a look at the vision receiver. Signals are supplied direct to the mixer, no RF amplifier. This was a common practise in early TV receivers. Because the intermediate frequency is low the four stage amplifier should provide excellent gain. The Mullard TSP4 pentodes have a gm of 4.2ma/V which is a good figure for early television RF pentodes. Because the set employs a large CRT a full wave demodulator is employed in order to avoid a fine dot pattern appearing on the screen. A Mullard 2D4A double-diode is used as the vision detector. A TSP4 is used as the video amplifier. Positive going video is supplied to the CRT grid via a capacitor. No DC restorer. DFWB. Attached Thumbnails Last edited by FERNSEH; 20th Feb 2019 at 12:30 pm.

27th Feb 2019, 12:31 am	#126
ThePillenwerfer Octode Join Date: Mar 2011 Location: Sheffield, South Yorkshire, UK. Posts: 1,453	Re: Baird T5 restoration project. Come on, David, let's have an up-date. The suspense is killing me: have the woodworm eaten you? __________________ "Experts are only good at one thing: explaining why something will not work!"

27th Feb 2019, 11:02 am	#127
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,375	Re: Baird T5 restoration project. "have the woodworm eaten you?" Hi Pillenwerfer, But they have made a good meal of every plywood panel. The control panel is the last cabinet part to be made and it is proving to be a bit difficult replicate but I will have something show on the forum by the weekend. The vision receiver and the power supply units are on the bench for servicing. We'll soon find out the intermediate frequency and the passband characteristics of the IF amplifier. DFWB. Last edited by FERNSEH; 27th Feb 2019 at 11:09 am.

27th Feb 2019, 5:56 pm	#128
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,375	Re: Baird T5 restoration project. Testing the power supply unit. The 16mfd reservoir capacitor and the 24mfd main smoothing capacitor were found to be useless so for the time being two 8 + 8 mfd capacitors will be used until the correct components can be found. Under no load and with only 150VAC supplied from the variac the smoothed HT voltage is 300V. Later today the vision and sound receivers will be connected to the power supply. DFWB.

27th Feb 2019, 7:03 pm	#129
ThePillenwerfer Octode Join Date: Mar 2011 Location: Sheffield, South Yorkshire, UK. Posts: 1,453	Re: Baird T5 restoration project. Good to hear that your steadily progressing. __________________ "Experts are only good at one thing: explaining why something will not work!"

28th Feb 2019, 11:28 am	#130
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,375	Re: Baird T5 restoration project. In fact as the picture shows I've little choice but to make a new control panel. DFWB. Attached Thumbnails

28th Feb 2019, 11:48 am	#131
ekjdm14 Banned Join Date: Feb 2019 Location: Congleton, Cheshire, UK. Posts: 609	Re: Baird T5 restoration project. Wow, only just seen this thread & the first thing that springs to mind is that episode of The Young Ones... "Vivien, eat the telly!" Right, now I've got that off my chest I shall go back and continue reading. It looks like one heck of a project and I doff my hat to you for taking it on.

1st Mar 2019, 3:09 am	#132
beery Heptode Join Date: Jun 2006 Location: Ware, Hertfordshire, UK. Posts: 984	Re: Baird T5 restoration project. Hi David, I'm loving the progress by the way. I've uploaded a photo of how the vision unit would have looked with the original capacitors. The electrolytics in the one you are restoring have been very neatly fitted, so I would say definitely a manufacturer's post war overhaul. Another thing I have noticed by looking at photos of other surviving T5 sets is that sometimes the speaker is on the other side of the cabinet. I can't see any reason why moving it to the other side would help really, so maybe it is just random... Cheers Andy Attached Thumbnails __________________ www.youtube.com/user/andyvalve100

1st Mar 2019, 12:47 pm	#133
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,375	Re: Baird T5 restoration project. Today's report is about the good progress I'm making with the sound and vision receiver units. The oscilloscope trace shows the negative going video present at the grid of the TSP4 video output valve. Despite having no RF amplifier the vision receiver has high gain. It has been established that the vision IF amplifier is aligned to the upper sideband which means there is a deep "trough" between the vision and sound passbands. The vision IF is 13mc/s, much higher than I thought it would have been. Much more work needs to be done on the vision receiver but the results so far are very encouraging. DFWB. Attached Thumbnails

2nd Mar 2019, 5:21 pm	#134
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,375	Re: Baird T5 restoration project. Today the new control panel was test fitted. The panel is canted back 35 degrees which made it necessary to adjust the angle of the cutting disc on that scary saw bench. DFWB. Attached Thumbnails

7th Mar 2019, 9:21 pm	#135
Magpie66 Diode Join Date: Jul 2018 Location: Chesham, Buckinghamshire, UK. Posts: 6	Re: Baird T5 restoration project. Hi Dave. Got one of those saws myself,not my favourite tool. Nice to see your progress on the T5. I remember you saying that you were enjoying this restoration. Hope the problems you have encountered haven’t changed your mind. Keep up the good work, Anthony.

7th Mar 2019, 11:24 pm	#136
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,375	Re: Baird T5 restoration project. Hi Anthony, The restoration of the Baird T5 is progressing well. Just two more jobs to do before the wood veneers are applied to the surfaces of the cabinet front panel, the control panel and the CRT screen panel. First task to do this weekend is make the specially shaped beading fitted between the control panel and the upper panel, see the attached pictures. It might be possible to use ordinary stock beading available from B & Q. Again, the saw bench will cut out the 30 degree chamfer. The second task is to make the cut out in the front panel for the door to access the timebase controls. DFWB. Attached Thumbnails

14th Mar 2019, 10:20 pm	#137
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,375	Re: Baird T5 restoration project. The cut out in the front panel for the timebase controls door was made today. The front panel is now ready for the surface veneers to be applied. DFWB. Attached Thumbnails

15th Mar 2019, 2:26 am	#138
beery Heptode Join Date: Jun 2006 Location: Ware, Hertfordshire, UK. Posts: 984	Re: Baird T5 restoration project. I see you have included a cat sized fire escape via the speaker aperture... __________________ www.youtube.com/user/andyvalve100

27th Mar 2019, 1:40 pm	#139
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,375	Re: Baird T5 restoration project. All the interior surfaces of the cabinet are matt black and of course the best paint for the job is that used for blackboards. DFWB. Attached Thumbnails

2nd Apr 2019, 3:37 pm	#140
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,375	Re: Baird T5 restoration project. Decisions, Decisions. The attachment shows two CRT support panels, the one on the left is the original and the other is the newly made replica. The CRT panel was the only plywood part in the set that wasn't totally destroyed by woodworm, only one corner of the panel had been invaded by the worms. So, the question is, in order to maintain some originality should the refurbished panel be used in the reconstruction or, should we play safe and fit the replica part? DFWB. Attached Thumbnails