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-   -   Baird Garrick (https://www.vintage-radio.net/forum/showthread.php?t=145778)

beery 18th Apr 2018 12:30 am

Baird Garrick
 
5 Attachment(s)
Hi All,
I've just obtained this Baird Garrick.

There are only a couple of valves present and the tube has been necked.
Also there was a mouse nest in the PSU section at the bottom of the set.

However it is not all bad. The cabinet has survived quite well and still has a good finish. There is no sign of damp (appart from mouse wee). All the electronics seems to be present.

I made a start by removing the mouse nest and cleaning away all the droppings.
The PSU although corroded on top due to the mice, actually looks like new underneath. There are signs that there was once a mains EHT transformer fitted, although there is no socket for and EHT rectifier on the PSU chassis.
I checked the date on one of the electrolytics to be March 1948.

I would apreciate any service info or photos that anyone has. A photo of the back cover could be nice for a start.

Cheers
Andy

rogerdup 18th Apr 2018 6:39 am

Re: Baird Garrick
 
Hi Andy,
The cabinet looks nice. I will follow your restoration of this set when you decide to start on it.
Regards,
Roger

Argus25 18th Apr 2018 7:35 am

Re: Baird Garrick
 
I wonder if the mice ate the speaker cone or perhaps harvested the cone to help make their nest.

Its a great looking TV!

FERNSEH 18th Apr 2018 9:09 am

Re: Baird Garrick
 
4 Attachment(s)
Hi Andy,
Here's some pictures of the chassis assemblies in another Baird theatreland model, the "Lyric".
The Garrick and Lyric TVs were part of a series of models manufactured after WW2. There was also an Adelphi model.
The story goes that J.L. Baird's friend Jack Buchanan financed the TV manufacturing project.

From Helensburgh Heritage:
http://www.helensburgh-heritage.co.u...ird&Itemid=457

DFWB.

FERNSEH 18th Apr 2018 9:25 am

Re: Baird Garrick
 
1 Attachment(s)
A picture of the power supply unit.

DFWB.

Jac 18th Apr 2018 9:52 am

Re: Baird Garrick
 
4 Attachment(s)
Andy,

Please find attached the images I have of a Baird Garrick.
No picture of the back I'm afraid.

Jac

Panrock 18th Apr 2018 3:41 pm

Re: Baird Garrick
 
A rare bird indeed! I will follow with interest.

Steve

mark pirate 19th Apr 2018 6:46 pm

Re: Baird Garrick
 
Glad that the set went to a good home, a very rare set.
I noticed the CRT was necked, by the look of the LOPT it looks to have been shedding hot wax recently, hope it turns out to be OK....
:beer:
Mark

FERNSEH 19th Apr 2018 8:30 pm

Re: Baird Garrick
 
1 Attachment(s)
The CRT is the Mazda CRM121 or CinTel 12MW3A.
The HT rectifier Mazda UU8. RF pentodes Mazda 6F12 = EF91/6AM6.
It's possible the timebase circuits are similar to the pre-war Baird TVs, those pole piece extensions about the neck of the CRT will confirm if that is so.
The timebase valves are likely to be the Mazda 6P28 although it's worth noting that Ambassador employed a similar circuit in the TV2 and the valves employed in that set were two 20P1s.
The revised attachment shows the frame transformer pole pieces.

DFWB.

Argus25 19th Apr 2018 10:26 pm

Re: Baird Garrick
 
1 Attachment(s)
Quote:

The revised attachment shows the frame transformer pole pieces.
That is really interesting. I wonder what the frame linearity was like ? The closest thing I have seen to this are some of the experimental TV deflection systems in Von Ardenne's book (attached image) where there was a picture of a large iron cored pole piece/frame def coil. I guess it makes sense to make the actual coil the frame oscillator too, as it could avoid a frame output and frame oscillator transformer

FERNSEH 19th Apr 2018 11:32 pm

Re: Baird Garrick
 
Pre-war Baird TV receivers employed extended frame timebase transformer pole pieces.
Link to the CRT replacement topic in my Baird T23. Post No.33 shows the transformer and it's extended pole pieces.

.https://www.vintage-radio.net/forum/...d.php?t=132064

Unsure if it was Baird Television Ltd or Fernseh AG that had developed this type of timebase generator.

DFWB.

beery 20th Apr 2018 10:07 am

Re: Baird Garrick
 
Hi all,
Thanks for your encouragement.

The speaker cone, yes some of it was found in the mouse nest. I'm not going to try to glue it back together ;)

I had the PSU on the bench last night and sketched out the circuit. It is indeed a UU8 that is required. I hope that's not too expensive.

I had a quick look at the sound receiver, indeed it seems to use 6F12 pentodes and maybe a 6D2 detector. I will trace out the circuit later. Interestingly the sound receiver is powered from the PSU in the radio, so I will probably start with the sound first.

The timebase section is all 4V, so I guess it would be a PEN46 used for each timebase output. I assume the line generator is a T41??
Anyway, a low current 6.3V feed goes to the timebase chassis to provide a 6.3V CRT heater option. This set has a Mullard MW31-14 or MW31-7 (the label is damaged). I think one of the photos of other sets shows this too. I intend to fit an MW31-74, but I need a cavity anode to top cap adaptor. I will place a wanted add for parts required.

About the chassis generally, it looks like an aluminium version of a Baird pre-war chassis. Indeed I think the pre-war Baird TRF unit would fit directly in place of the vision receiver.

More to follow this weekend as I start to draw up the circuits.

Cheers
Andy

Heatercathodeshort 20th Apr 2018 10:19 am

Re: Baird Garrick
 
I have a clip to cavity connector converter you can have FOC. If you would like it, please send me a PM and I will post. John.

FERNSEH 20th Apr 2018 11:52 am

Re: Baird Garrick
 
1 Attachment(s)
The timebase circuits of the Ambassador TV2.
Line and frame timebases are of the self oscillating type.

The earlier model TV1 employed thyratron oscillators.

DFWB.

FERNSEH 20th Apr 2018 2:17 pm

Re: Baird Garrick
 
1 Attachment(s)
The sync separator in the Ambassador TV2.
The 6F13 can be substituted with a 4volt Mazda SP41.

DFWB.

beery 21st Apr 2018 1:55 pm

Re: Baird Garrick
 
Quote:

Originally Posted by Heatercathodeshort (Post 1036661)
I have a clip to cavity connector converter you can have FOC. If you would like it, please send me a PM and I will post. John.

Thanks John,
I'll send you a PM.

Cheers
Andy

beery 26th Apr 2018 1:21 pm

Re: Baird Garrick
 
5 Attachment(s)
Hi all,
Here are some photos of the TV section.

The mask is completely unuesable, I plan to use the mask from a TV24 for now, but I don't know how to hold the CRT in place as it does not wrap around the bulb of the tube as the existing mask does.
Any suggestions?

The third photo shows a neon regulator an odd thing to find in a TV you might think, but then it is a Baird. However the nipkow disk that should go in front of it is missing :-D

The fourth photo shows the rogue line output and EHT transformer. It looks rather like the lopty from a Baird Townsman, so was it from a Baird repair?

The underside looks fairly straight forward though.

Cheers
Andy

mark pirate 26th Apr 2018 3:18 pm

Re: Baird Garrick
 
Quote:

The fourth photo shows the rogue line output and EHT transformer. It looks rather like the lopty from a Baird Townsman, so was it from a Baird repair?
It looks the same as the one in my T164 portable, definitely a Baird part.
Was it originally mains EHT?
I wonder if you could use webbing straps to hold the CRT in place, as seen on many HMV/Marconi sets?
:beer:
Mark

Jac 26th Apr 2018 3:43 pm

Re: Baird Garrick
 
Quote:

Originally Posted by beery (Post 1038437)
The fourth photo shows the rogue line output and EHT transformer. It looks rather like the lopty from a Baird Townsman, so was it from a Baird repair?

Hi Andy,

The LOPT also looks the same as the one in my Baird T29A.

A mask can be made from MDF material. I did this for a Philips 383A and for a Pye 817.

Jac

beery 29th Apr 2018 9:08 pm

Re: Baird Garrick
 
3 Attachment(s)
Hi all,
Thanks for all your ideas and encouragement.

I'm not quite sure yet what to do about the tube mounting.

Yes, it had mains EHT originally and the mounting points for the EHT transformer etc have been used in the past. For now I will restore it as it is, with a view to converting it back as soon as I know the transformer rating etc.

I spent friday night at my parents house and went hunting for parts.
I now have most of the valves I need and many other parts, some of which are shown in the first photo.
I found 3 UU8 valves!, but only one PEN46 and it does not look too clever.
I did not have any 6F12 valves, so I will have to fit EF91 valves for now, which hopefully won't affect the alignment too much. Luckilly it looks like the RF coils have never been got at and I don't intend to touch them either.
I could not find a 10" speaker unfortunately.

The second photo shows a new MW31-74 CRT. I still need an ion trap magnet for this.

The third photo shows the anode cap adaptor which Heatercathodeshort kindly sent me. This allows me to use a later CRT without changing the anode connector.

Restoration has now started and is continuing on several fronts simultaneously. However, I shall write it up chassis by chassis. The aim is to get the sound working first.

Cheers
Andy

beery 29th Apr 2018 9:26 pm

Re: Baird Garrick
 
2 Attachment(s)
Hi all,
Here is the TV sound section of the Baird.

There are no waxies in the sound section, so a quick clean up with an oil soaked scouring pad was all that was needed.
This chassis is made of tin plate, so I had to be gentle with it. I did not want to use rust converter or anything like that as I am mindful of not wanting to mess anything up, given that there is no service info available.
I also fitted the missing valves and a sensitivity control knob. The original style knob is probably impossible to find, but as it is an internal control I'm not too bothered.

I've not needed to draw out the circuit for this at present. Hopefully I won't need to revisit this chassis, although it is very easy to get to. I will however change the cable mounted octal plug that is fitted to this chassis as soon as I get hold of one as the locating spigot is missing.

The TV sound output is stage is located in and shared with the radio section, so this is my next area of focus as well as the TV PSU as both have parts that require painting.

Cheers
Andy

beery 9th May 2018 11:48 pm

Re: Baird Garrick
 
2 Attachment(s)
Hi All,
I've now gutted and re-stuffed the electrolytics from the TV PSU and the radio chassis.
I used 10uF film capacitors to replace the original 8uF sections in the TV PSU. I would not normally use these as they are much more expensive than electrolytics, but I managed to obtain quite a number of them from old high quality fluorescent lighting balasts that were being thown out at work.

The second photo shows the capacitors glued back together with epoxy resin and temporarily held together with tape whilst the glue sets.

Cheers
Andy

beery 11th May 2018 7:42 pm

Re: Baird Garrick
 
4 Attachment(s)
Hi all,
I've now put the PSU back together.

When I initially drew out the circuit, I found that two resistors in series were providing a link between the timebase HT and vision strip HT. Originally one resistor would have been used, but presumably the original burnt out. Of the two that were fitted one was also burnt out and the printed value was burnt off too.
I suspect that there will be a leaky wax decoupling cap in the vision section that caused the overload in both cases.
The outer ceramic covering of the burnt out resistor was removed so that a good section could be measured to work out the aproximate value. It worked out to be 1.2K to 1.3K ohms, which with the other resistor of 330 ohms works out to be a 1.5K resistor aproximatley.

A new 1.5K 14W resistor was fitted and positioned slightly further away from the wiring than the previous two in order to protect the insulation of the transfomer wires which were slightly burnt when the resistor originally failed.

The second and third photos show the before and after of the underside of the PSU. I refered to the earlier photo when re-fitting the electrolytics so that they were rotated round exactly the same way in their clamps.

The fourth photo shows the top view of the PSU. The transformer now looks a little bit untidy next to the newly painted smoothing choke. I might paint it in situ at a later date, but for now I must focus back on the radio section.
I've not tested the whole PSU yet as I need to attach a load to it first. I have tested the transformer though and it runs nice and cool.

Refitting the mains EHT is a job for much later, it can wait for now, but I am accumulating the necessary parts.

Cheers
Andy

red16v 12th May 2018 9:18 am

Re: Baird Garrick
 
I came into telly bashing in the 80's working on broadcast monitors so the circuits involving valves etc are a compete mystery to me!

Just wanted to say how much I am enjoying your restoration, I hope it won't sound too condescending to say I admire your ingenuity and your 'cunning' methods to disguise new parts as old parts! I only wish I understood the technical descriptions of how the circuits work.

Really enjoying your updates and I'm looking forward to seeing the final set with pictures (and maybe sound via youtube?).

dseymo1 12th May 2018 11:55 am

Re: Baird Garrick
 
I'll remember your technique of measuring what's left of a burnt-out resistor. Wouldn't have occurred to me, but potentially very useful!

beery 22nd May 2018 12:13 pm

Re: Baird Garrick
 
4 Attachment(s)
Hi everyone,
thanks for the messages of encouragement. This is quite a long slog, but it keeps me out of mischief.

Remember the mouse eaten speaker? I've included a photo of the front of it just to show how bad it was.
I managed to obtain a period speaker from ebay which thankfully had a mounting point for an output transformer.
The output transformer was removed from the original speaker, but is was too big for the mounting on the new one, so instead I fitted a transformer recovered from a pre-war HMV radio.
The speaker has now been fitted to the set and it looks like it has always been there :)

The radio unit is slowly going back together, it still need its waxies replaced, but I may do this one at a time due to there being no circuit diagram available.

Cheers
Andy

McMurdo 22nd May 2018 9:09 pm

Re: Baird Garrick
 
Watching intently, Andy. I was one of no doubt many who was tempted to buy this then chickened out in deference to some higher being.

beery 8th Jun 2018 1:18 pm

Re: Baird Garrick
 
4 Attachment(s)
Hi all,
progress has been slow and some of my time has been spent winding prototype switched mode (flyback) transformers for work.

The photos show the initial condition of the radio section, although I've added a few valves in this photo.

The next two pictures show the cleaning of the chassis.

The fourth photo shows the current state of the underside of the chassis, with most of the waxies rebuilt and temporary electrolytics tacked in.

On power up the HT rail was found to be about 100V to high, this is due to the mains transformer having been replaced in the past with one that does meet the original spec. I've now added a 1.5K resistor in the smoothing circuit to compensate for this for now. I'm looking to rewind or replace this transformer.
The radio showed signs of life on MW, but SW turned out to be very deaf. However this may not be a fault as it is hard to pick up any radio in Ware. I will check the alignment though.
I also tried the TV sound section and it works, though again, not very sensitive, but this is unrelated to the SW insensitivity.

I'm planning to have a look at another set this weekend to take some measurements and see how the back panel is made, as well as have a look at the EHT section.

Cheers
Andy

beery 29th Jun 2018 10:37 pm

Re: Baird Garrick
 
5 Attachment(s)
Hi all,
Yes, slow progress on the Baird again.

I was able to pay a visit to another TV collector who has the only working example of one of these sets that I know of, though his is actually a Lyric, which uses the same chassis. It worked quite well acutally
By taking some measurements on the working set I was able to ascertain that the non-original mains transformer in the radio section is indeed giving out too many volts, so I will have to replace it.

I've attached a photo of one of the smaller electrolytics from the radio chassis. These capacitors are hard to restuff especially when (as in the case of this capacitor) they are not held in place with a clamp. The only option seems to be to cut the capacitor length ways, though this means they never go back together properly. Anyway, you still can't see it when the capacitor is back in its original position.
I have now rebuilt all the capacitors in the radio section. One thing I found along the way is the poor standard of construction. Whilst all the solder joints are good, none of them are properly mechanically secured. Where wires and components join to solder tags they don't pass through the tag eyes, but are merely pushed against the side of the solder tag ???

I had to replace the smoothing choke in the radio section as I have taken the original to form the line output transformer. The original choke was 10H 170 ohms which is overkill, but it was really designed for the TV PSU which has an identical choke.
A replacement choke was given to me, but it measured 3H 68ohms. I wanted at least 5 henries and something nearer the right resistance. I unwound it and found it had 2080 turns of 31 SWG wire. Experience led me to pick two sizes smaller, so I filled the former up with 33 SWG, of which I managed to fit 3250 turns, which came out to 6H 155 ohms. In order to measure the inductance the core has to be reassembled together with the core gapping paper.
After putting the choke together I decided I really needed to clean and paint its rusty U clamp, so until the paint hardens I can't try it.

I now need to look at the problem of the mains transformer, before I try to solve the problem of mains hum on 405 line sound. The hum is not helped by the fact that the set does not switch off the audio when switching between radio and TV, it merely switches the heater supplies over from the radio RF/IF to the TV sound receiver.

I've removed the vision reciver from the TV section and this revealed yet more mouse droppings :'( It also showed up a mystery, a missing valve which I assumed is an SP41 has a grounded top cap or grid, very odd.

I've also included a nice photo of the position of the contrast control. Not only have you got to remove the back and run the set with its nasty exposed mains EHT (more on that when I get an EHT transformer for it), but you have to reach right in and run the risk of breaking the CRT vacuum pip when adjusting it :o So why put it there, why not put the pot shaft sticking out of the rear of the chassis?? Answers on a postcard please.

That's all for now.

Cheers
Andy

mark pirate 2nd Jul 2018 8:22 am

Re: Baird Garrick
 
Quote:

I've also included a nice photo of the position of the contrast control. Not only have you got to remove the back and run the set with its nasty exposed mains EHT
That is utter madness, at least the pot could have been fitted to the rear end of the chassis?
I have to agree about the poor build quality of Baird sets, My T164 is no where near the quality of it's peers of the time, but apart from the very poor CRM92, performs quite well.
:beer:
Mark

Panrock 2nd Jul 2018 7:24 pm

Re: Baird Garrick
 
Quote:

I have to agree about the poor build quality of Baird sets
With my Baird Townsman, I gave up - and installed a Bush TV24A chassis. A great improvement.


Steve

beery 1st Aug 2018 10:12 pm

Re: Baird Garrick
 
5 Attachment(s)
Hi all,
so the saga of the radio section of the Baird continues.

One of the issues was that the original drop though mains transformer had been replaced with an enclosed chassis mounting type which also produced HT which was 100V too high!

First I took one of the end covers, cut its legs of and made a slot for the voltage ajustment panel.

Then I unwound the secondaries of the transformer. With a drop through transformer we need all the wires to come from one side of the windings, ie. we cannot have wires that have to run past the lamminations. One way of doing this would be to rewind the primary with the wires emerging at the correct point. However, I decided to take the easier route of fitting a couple of wires to take the live and neutral connections round to the other side of the transformer. To do this I had to drill some extra holes in the coil former without damaging the primary winding and a strip board track cutter proved perfect for this.

The transformer, accounting for load worked out at 6 turns per volt, so 1500 turns of 36 SWG wire were wound for each half of the HT winding. Then 30 turns of 18 SWG for the rectifier heater, followed by 38 turns of 19 SWG for the 6.3V heater supplies.

I painted the top cover and cut some Nomex paper to insulate around the voltage selector.

With the transformer back in place the chassis is looking much more like it should do. The HT is now correct at 250V DC.

Extra hum and occasional bright purple fireworks with spectacular yellow sparks flying off its cathodes pointed to a very unhappy 5Z4G. A replacement restored reliable operation of the radio.

Hum was still a problem with the TV sound though and this was traced to a poor connection between the chassis and a solder tag which provides the ground return for HT, Heaters and audio from the TV sound unit. I added a wire from the tag straight to the grounding point of the 6.3V heater winding from the mains transformer and that cured the problem.

The next thing is to make a cover plate to blank off the holes in the chassis where the mains adjustment had once been fitted. I also need to re-align the TV sound unit.

In other news, I now have some lovely 9mm playwood for the back panel and have made a template from another collector's Bair Lyric. The two cabinet styles are very similar in overall height and width, but the chassis' are mounted at a different height to my set, so a little more work is needed to establish where everything goes.

That's all for now. Plodding on slowly, plod, plod...

Cheers
Andy

beery 1st Aug 2018 11:11 pm

Re: Baird Garrick
 
Hi all,
I've just noticed I said 'playwood', well I don't know what that is, maybe it is a bit like plywood, but more fun. BTW 9mm plywood for a back panel is plain bonkers of course, what was wrong with a bit of cardboard?

Cheers
Andy

Heatercathodeshort 2nd Aug 2018 7:11 am

Re: Baird Garrick
 
Yes! My old Gran would have said 'All show and no knickers'. Crazy overspend on the cabinet and a load of rubbish inside.
HMV did the same thing with the 1807. John.

beery 14th Aug 2018 6:52 am

Re: Baird Garrick
 
4 Attachment(s)
Thanks for the encouragement John.

So, much like my crazy overspend on a valveless cabinet and a load of mouse :censored: inside then...

Sometimes external events influence the order in which a project progresses and indeed this is what is now happening here, in a good way though :)

A week's visit to my parents place provided the opportunity to use the vice mounted folding tool to make up the supporting bracket for the EHT rectifier.

First folded to shape, drilled and then a q-max cutter was used to make the hole for the valve socket. Finally the top radius was added and then a check to see what it looks like in the set. Yes folks the EHT capacitor does sit off the edge of the chassis (the original cap was even bigger!) and yes the entire bracket is at EHT potential ;D

Now back home, but with my wife and daughter at my parents for another week I can do some noisy bits (my daughter's room is above my work room), so work on the cabinet back has now started.

Cheers
Andy

line sync 14th Aug 2018 8:04 pm

Re: Baird Garrick
 
Hi Andy
I like that vice mounted bending jig , very useful bit of kit.
Keep up the good work.

Robin

beery 4th Sep 2018 2:38 pm

Re: Baird Garrick
 
5 Attachment(s)
Hi all,
an update on the Baird.

I drew out the circuit of the TV sound section (attached). Notice the inefficient capacitor coupling between stages. Also the aerial input coil needs to be terminated with load of the aerial input of the vision section in order to work properly.

The TV sound section was unstable at high gain. I found that C4 was missing and that R7 had been replaced with 100 ohm and 150 ohm resistors in series. The remains of C4 could be seen soldered to the chassis, so I found suitable vintage parts and fitted them. The sound TRF unit is nice and stable now.

I made a small aluminium plate to cover the hole that had been left by moving the mains voltage selector. I also replaced the 50s double insulated mains input cable with a twisted pair of blue and black wires as it would have had originally.

The back cover of the set has now been drilled and routed and the brass screw cup inserts have been fitted. The mains input hole needs to be filed into a slot and the CRT neck box needs to be assembled.
The rear controls do not extend as far as the back panel, so it is a case of having to stir around the controls with your fingers! To make things more interesting the identity of the rear controls are not marked on the rear panels of the other sets I have seen.

That's all for now.

Cheers
Andy

FERNSEH 5th Sep 2018 11:39 am

Re: Baird Garrick
 
Hi Andy,
That's a very nice back you have made for the Garrick cabinet. I'd image that the CRT neck protection box will be made from wood also.

Will it be painted black or simply left in the condition it is now?

Excellent circuit diagram of the sound RF amplifier and demodulator. Audio output is positive going so no possibility of AVC. Note the simple noise limiter, clips the positive going spikes.

DFWB.

beery 5th Sep 2018 3:11 pm

Re: Baird Garrick
 
1 Attachment(s)
Hi David,
thanks for the comments. I've attached the only picture I have of a Garrick back. The back on the Lyric that I have been using as a reference has a slightly different back because the timebase chassis and radio sections are at different heights in the cabinet compared to the Garrick.

So, yes the neck box is also wood and the whole lot will be painted black

Cheers
Andy

beery 7th Sep 2018 12:29 am

Re: Baird Garrick
 
3 Attachment(s)
Hi all,
I've attached a photo of a Baird Lyric back as reference for the kind of thing I am aiming for with the replacement back panel for the Garrick.

The vision RF unit has now been cleaned up ready for evaluation. One photo shows what a couple of the heater decoupling capacitors looked like after cleaning, to the right of them you can just make out the two that still needed cleaning.
The last photo shows the finished look after rubbing down with an oil soaked scouring pad.

The cleaning of the RF unit involved and unpleasant and surreal task. Yes, I say surreal because never in a million years would I have thought that I would end up spending an evening removing individual mouse turds from a TV set's RF coils with a pair of tweezers :'( Still, it's all part of the hobby I suppose ;D

Cheers
Andy

red16v 7th Sep 2018 7:39 am

Re: Baird Garrick
 
Enjoying your updates, well done so far.

beery 8th Sep 2018 11:24 pm

Re: Baird Garrick
 
1 Attachment(s)
Hi all,
Thanks again for people's encouraging comments.

I've attached the diagram for the vision TRF section. Do have a look, it is very unusual. If I had not drawn it out then I would have put the detector valve in the wrong socket for sure.
I've never seen push-pull video drive before. However I assume that vision output 1 is for the CRT (as it has a peaking coil) and vision output 2 is for the sync separator. I've not traced out the CRT connections, so I can't say for sure.

Cold checks have revealed that R8 has increased in value by 10 times and is looking decidedly brown. R14 is also high an a little bit discoloured.
The really odd fault is that VR1 is open circuit at both end connections, in that there is no reading between them and no reading between either terminal and the wiper irrespective of the wiper position; that's a new one on me.

I'm not sure how much more work I will do on it for the time being as I am gearing up for a trip to Malaysia in a couple of weeks, so I really do need to take time out to pack...

Cheers
Andy

line sync 9th Sep 2018 8:54 am

Re: Baird Garrick
 
Very neatly drawn circuit diagram of the vision RF stages andy , must have tock you a while to do that.
I`m enjoying reading about your progress with this set .

Robin

whiskas 9th Sep 2018 10:29 pm

Re: Baird Garrick
 
Nice to see your updates on this restoration - hope you get it fully working in the end!

beery 16th Sep 2018 7:11 pm

Re: Baird Garrick
 
5 Attachment(s)
Hi All,
I'm sure this really is my last update before Malaysia.

Quote:

Originally Posted by line sync (Post 1073706)
Very neatly drawn circuit diagram of the vision RF stages andy , must have tock you a while to do that.
Robin

Thanks Robin.
Drawing circuits is part of my day job, though there are no valves used at work! When I started drawing out the sound circuit I started off using rectangular resistor symbols which looked out of place, so I changed them for the zig-zag style symbol. I also made a mistake in the vision circuit in that the sensitivity control should actually be labled contrast.

Anyway. I unsoldered the contrast control (VR1) and found a dry joint at one end, so now I had end to end continuity, but nothing on the wiper. I took the control apart by squeezing its metal body slightly with pipe grips so that the metal end cover came off. I did bend the wipers in the process, so I couldn't say what was causing the problem. After bending the wipers to shape and greasing the wirewound track it seemed to work ok.

I replaced R14 (10K) with a vintage type. R8 (5K1) I had to replace with a vintage 4K7 type. Interestingly if I heated up R8 very hot with a soldering iron it would read ok until it cooled and flicked back to around 50K, very odd.

I fitted EF91 pentodes and an EB91. I connected the vision reciever to the HT of the radio and connected the heaters to the DC bench supply set to 6.3V. I hooked up the scope to vision output 1 and fed in test card C from the Aurora and hey presto it worked :D

So the photos show the contrast control, R8 before and after replacement, the RF unit connected to the radio chassis and the output on the scope.

Cheers
Andy

FERNSEH 16th Sep 2018 10:12 pm

Re: Baird Garrick
 
Hi Andy,
everything is looking good. Your set is going to be the best of the surviving Baird "Theatreland" sets.
I notice that there is two vision demodulators feeding separate video amplifiers. I presume the amplifier with the anode peaking coil supplies positive going video the CRT modulator grid and the other negative going video to the sync separator.

DFWB.

beery 24th Oct 2018 7:05 am

Re: Baird Garrick
 
5 Attachment(s)
Hi all,
Whilst the rest of my family stay on a few more weeks in Malaysia, I am back home and so have the house to myself to do some of the bigger jobs.

The first photo shows the neck box being constructed for the back panel. The box is 7" x 7" x 3 1/2" which is ridiculous really.

The second photo shows the neck box being clamped to the back. After this the back was flipped over and the pilot holes were drilled through for the neck box mounting screws.

The third photo shows the start of painting the back. Towards the top of the photo you can just see the painted neck box. The main back panel has just had the inside of all the holes painted at this time.

The fourth photo shows the vision chassis as it was when I obtained it.

The fifth photo shows how shiny the chassis is after cleaning. The vision receiver has been removed from the left hand side, and on the right hand side the rogue line output transformer and a choke have been removed to facilitate the chassis cleaning.

Cheers
Andy

beery 31st Oct 2018 2:12 pm

Re: Baird Garrick
 
5 Attachment(s)
Hi all,
An update on the Baird.

The back cover is now finished, it just needs some replica labels to be made for it.

I've replaced the CRT socket with a Duodecal type to fit the new tube and replaced the rubber wiring on the socket. I've kept the rather messy look of the wiring.

I've also replaced the rubber wires running from the PSU plug to the timebase chassis.

I've has a quick go at cleaning up the cabinet and have put the radio chassis inside.

The last photo shows the view looking down through the CRT protection glass to the glowing valves of the radio chassis.

I've started to draw up the timebase chassis, but I'm now taking a little break from the Baird whilst I go back to the HMV 905 for a bit.

Cheers
Andy

beery 9th Dec 2018 8:54 pm

Re: Baird Garrick
 
2 Attachment(s)
Hi all,
just a very quick update on the Baird.
Progress seems slow at the moment as I am also working on the HMV 905.

Another transformer clamp and the focus coil have been cleaned up and painted. No photos of these yet.

The PSU chassis now has an EHT transformer thanks to Mike Barker. This is from and HMV 1805. It fits the mounting holes, but is a bit taller than the original transformer, so I will have to re-make the bracket for the EHT rectifier to be a little taller.

I'm also making up a tube clamp. This is based on the early type of TV22 (non-ion trap CRT) of which I have included a photo. It is made of 1mm thick brass.

That's all for now.

Cheers
Andy

line sync 9th Dec 2018 10:39 pm

Re: Baird Garrick
 
Keep up the good work andy.

Robin


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