Re: Baird Garrick
 

The HMV 1805 EHT transformer will provide 6 to 6.5KV which is possibly higher than that was delivered by the original Baird transformer.
The 0.1microfarad EHT smoothing capacitors in the HMV 1805/6 are rated at 7KV.

DFWB.

Re: Baird Garrick
 

Just out of curiosity, did you supply the HMV 1805 transformer to Mike to be rewound? Or did Mike supply the EHT transformer? (i.e. you didn't have one?) :)

Edit: in hindsight that sounded a bit impolite. What I meant to say is does Mike also supply transformers, rather than just rewind ones you send. My brother Draenog doesn't have an EHT transformer for his HMV 900 which makes the difference interesting.

Thanks Phillip

Re: Baird Garrick
 

That's a new one on me too, in the same pot.

I experienced that in combination on two pots when I was restoring the HMV 904. On one the carbon track had visibly broken about 10% from one terminal hence no connection end to end. On the other one bad handling meant the wiper had broken from the shaft, which was rotating freely, and the wiper wasn't connecting to the carbon track.

To have both those faults in the same pot is probably fairly unique :)

Please say what you discover is the cause ... Bad connections on all connections would be the mundane answer :(

As far as what I did to fix things, I superglued the wiper back onto the shaft (the original mounting had been shattered), and used silver paint to reconnect the carbon track.

Re: Baird Garrick
 

Hi Phillip,
sadly I doubt that Mike has a supply of original EHT transformers.
He can certainly make one from scratch as he did for my HMV 905 from which it was missing entirely.
For the Garrick, what was needed was a potted transformer and it was fortunate that Mike happened to find one.
From what I can tell, the Garrick had a choice of the T5 EHT transformer or another type which might be made to the Bush T91 design (I can't verify the T91 theory). Either way, both choices were potted, though the T5 transformer is much smaller and possibly has lower EHT than the other option.

About the contrast pot. I was never very clear about what the trouble was, so I am prepared that it may become intermittent in future. The carbon and the wirewound pots seem to be based on american designs (reliance branded), indeed the pot that gave you trouble in your 904 would have been american I think.

Cheers
Andy

Re: Baird Garrick
 

Hi All,
I've now made the CRT clamp that will enable the new tube to be held in place without a wrap around mask.

The first photo shows the dimensions (based on a TV22 CRT clamp).

The second photo shows a cardboard prototype.

The third photo shows a piece of 1mm thick brass cut to shape.

The fourth photo shows it folded into shape.

The last photo shows the clamp fitted in place on the old broken CRT (the focus coil is not fitted at present).

I need to find a brass (non-magnetic) screw and nut to finish it off.
That will be all for a while. First there is Christmas and then when we get back we have to deal with an unexpected house move.

Merry Christmas
Andy

Re: Baird Garrick
 

Hi Andy,
another very nice metal fabrication job. Good idea to use a down to air CRM121 CRT for test purposes. I'm doing the same for my Decca 101 recreation project.

DFWB.

Re: Baird Garrick
 

Hi all,
well it has been a very long time since my last post.

Now settled down in our new home, so ready to tinker...

I obtained a 0.1uF 7KV Visconal which I chain drilled on the base to open it up.
I then emptied it out (with precautions) and re-stuffed it with a new 8KV capacitor obtained from China.
I filled the base of the Visconal can with cut up lengths of hot melt glue sticks and then stuck the base on with a glue gun. The gaps from the chain drilling were filled with more hot melt. To keep the base straight whilst cooling. I bolted it to an empty baked been tin which I had drilled a hole in.

I re-made the EHT valve's mounting bracket. This time I made it 1 1/4" taller to clear the large EHT transformer. I also fitted the correct type bulgin style valve socket this time.

I then temporarily wired up the heaters to the EHT rectifier, attached my meter with a X10 probe and powered it up...

Hey presto, 5.83KV! I must admit that I was :censored: myself whilst doing this test, bearing in mind that the whole bracket is at EHT potential and also there being no bleader chain (there never was!).

That's all for now.

Cheers
Andy

Re: Baird Garrick
 

Switch Off
Isolate
Dump
Earth

8-o 8-o 8-o


Sterling work there Andy! Has anyone ever tackled another Garrick?


Steve

Re: Baird Garrick
 

Hi all,
finally back to mouse turd central.
After removing the scanning gantry (I'm not sure yoke is the right term for this design), I was able to clean behind it. This as the last part of the chassis that had to be cleaned and yes, turds galore, but hopefully that is the last of them.

Now I have started to put it back together. I still have to fit the lopty and then it is time to rebuild the caps in the timbases.

Oh yes, in answer to Panrock's question back in May...

I know of two surviving Lyrics, one of which has been restored to working order. These use the same chassis and I have been able to take electrical measurements from the restored set thanks to the kind owner.
I have not found any surviving Adelphi sets (same chassis again) or even a photo of one.
Including my set, I have found three Garricks. One (with a different coloured cabinet) is in a museum and the other is privately owned, but, in storage and unlikely to be restored anytime soon.
So as far a Garricks go, no, I don't know of any working examples...

Cheers
Andy

Re: Baird Garrick
 

Great work Andy! Yes I know of another guy that has tackled with success, another Garrick.

Can you believe that EHT capacitor mounted at the back of the chassis...Yes it is correct even to the overhang. It's the first thing your cat would ponce on when you took the back off! Lethal, no wonder very few of these receivers survived. Regards, John.

Re: Baird Garrick
 

Who designed these sets, was it Bush?

Peter

Re: Baird Garrick
 

Nothing to do with Bush Radio although some design elements of the T5 were incorporated in the Theatreland models. Most notable is the frame scanning system which employ extended pole pieces from the oscillator transformer.
There is evidence that the first Ambassador TVs used some of the technology from the Theatreland Baird sets.
Wasn't the post-war Baird TV manufacturing financed by J.L.Baird's friend Jack Buchanan? http://www.bairdtelevision.com/Buchanan.html

DFWB.

Re: Baird Garrick
 

Thanks for the info Andy.

Shouldn't that read "very few of the owners survived"? :laugh2:

Steve

Re: Baird Garrick
 

Hi Peter,
well as Fernseh points out obviously not Bush, but then again Bush must get some credit as most of the design is lifted from the pre-war Baird T18. The timebase has seen the simple change from B5 Cossor 41MP output triodes to Mazda octal PEN46 pentodes which are triode connected. Similar changes are found elsewhere in the set, but the design is really the television part of a T18 with updated valves. The only new parts of the design are the RF stages.
Anyway, I have no clue as to who updated the design and re-designed the sound and vision RF stages.

I've included a picture of the scanning yoke from the T18 so you can compare it with the photo in my last post. I should measure the coil resistance values and check them against the T18 manual.

Cheers
Andy

Re: Baird Garrick
 

Thanks David and Andy,

Yes, thumbing through Baird's biography co-authored by Malcolm Baird it looks as if in July 1944 Baird wrote to Buchanan with a view to setting up "John Logie Baird Ltd" along with his lawyer Shelley for the manufacture of television receivers and also cinema television.

In terms of receivers, their first was the giant Grosvenor of which only one was ever made and it appeared in early 1946. It looks as if the 27" CRT was an in house product but Plessey provided the television chassis, radiogram and cabinet.

After Baird's death and under Buchanan's chairmanship the theatreland models were apparently built at a factory in Rayner's Lane, Harrow and the Grosvenor was intended to be the top of the line model.

Peter

Re: Baird Garrick
 

A similar frame timebase circuit was used in the Ambassador TV2. See post #14. It would be interesting to find out which company designed the frame timebase. The original Baird company had links with Fernseh AG.

https://en.wikipedia.org/wiki/Fernseh

DFWB.

Re: Baird Garrick
 

I see a reference to a Baird Patented vertical deflection here:
https://www.earlytelevision.org/fernseh.html

I've emailed Darius asking if he knows the patent number.

Peter

Re: Baird Garrick
 

I've had a look through a stack (180) of Baird patents but I can't find it and unfortunately Darius can't locate it either.

In the biography there is a reference to "Baird's former assistant Anderson, who had continued with the company as technical partner, was asked to develop a table-top television set for the American standards."

The name EDWARD GEORGE ORME ANDERSON does appear in some of the Baird patents so he may have been the circuit designer of the "vertical deflection" circuit.

Peter

Re: Baird Garrick
 

From google patents, an amplifier attributed to Edward George Orme Anderson.
https://patents.google.com/patent/US2537807

Patent filed 1951 as a phase splitting amplifier. But this amplifier which employed the Mullard TSE4 secondary emission valve was used in this application in 1938 in the Baird T20 and T23 TV receivers.

DFWB.

Re: Baird Garrick
 

There are lots of Baird patents from the mechanical era and I didn't inspect many from the early 1930s but I think I looked at most of the mid 30s onwards. I did come across the video amp one but nothing that looked like a vertical deflection circuit. I am skeptical about JLB being a circuit designer. I was just clutching at straws with Anderson in my ignorance of any other obvious name. I did try looking at Geoffrey George Bernard, A. G. D. West, Paul Vernon Reveley, Alfred Sommer apart from JLB himself without success.

Peter

Re: Baird Garrick
 

I wonder if it might be Rudolf Jan Hamilton Forman?
https://worldwide.espacenet.com/publ...=&locale=en_EP

Peter

Re: Baird Garrick
 

Hi Peter,
you might be on to something. However this patent is about line deflection. Note that it mentions 6kHz which is 25Hz x 240 lines. It could well be the same person who designed the frame deflection as well though.

Cheers
Andy

Re: Baird Garrick
 

Hi Andy,

There is some similarity.

Peter

Re: Baird Garrick
 

Also:

https://worldwide.espacenet.com/publ...FT=D&DB=EPODOC

https://worldwide.espacenet.com/publ...FT=D&DB=EPODOC

https://worldwide.espacenet.com/publ...FT=D&DB=EPODOC

https://worldwide.espacenet.com/publ...C&locale=en_EP

Re: Baird Garrick
 

From the Baird Television website. About Jan Forman:

http://bairdtelevision.com/forman.html

DFWB.

Re: Baird Garrick
 

I think this is the patent that describes the combined frame oscillator transformer and scan coil.

https://worldwide.espacenet.com/publ...C&locale=en_EP

There are also some further patents from George Richard Tingley relating to the front scanned CRT used in the 27" Grosvenor and the 11" front scanned projection tubes.

https://worldwide.espacenet.com/publ...C&locale=en_EP

Peter

Re: Baird Garrick
 

Hi Peter,
That looks like the frame scanning patent we're looking for although the text doesn't mention anything about the pole extension pole pieces.

The text does mention extra the winding on the transformer used to counter the standing valve anode current. Without this winding the picture will be deflected off the screen.

The Murphy V136 of 1948 employed a self oscillating frame timebase. In this receiver the frame oscillator transformer is also the scanning yoke.

That projection CRT used in the Grosvenor set is an interesting device. Some provision for keystone correction of the raster will be necessary.

DFWB.

Re: Baird Garrick
 

Hi David,

Perhaps Tingley thought it unnecessary to show the pole piece configuration because anyone using the GB463972 description would be forced to use extended pole pieces anyway. The other Tingley patents I mentioned do show extended poles in their figures.

As I understand it there were two televisions showing the 1946 victory parade in the Savoy. One had a 5' projection display that magnified the image from an 11" front scanned CRT and the other was the "Grosvenor" which had a 27¾" front scanned CRT viewed directly. I think there was talk of using the "Grosvenor" CRT for larger projections but that probably got overtaken by the "Teapot" projection CRTs.

Peter

Re: Baird Garrick
 

As Peter says, look at page 5 of the above patent. It clearly shows the extended pole pieces

Peter, How do you find all this stuff?

Cheers
Andy

Re: Baird Garrick
 

Hi Andy,

Nothing clever I'm afraid. Just searching in Espacenet for any likely inventor names and sometimes one leads to another. "John Logie Baird: A Life" also gave a few starting points.

Thanks for the page 5. I missed that.

Peter

Re: Baird Garrick
 

The Fernseh DE6 didn't employ the Baird patented frame timebase transformer with the extended pole pieces. The scanning coils look like a conventional type. Chassis construction different from the Baird T5.
Link to a topic about the DE6: https://www.vintage-radio.net/forum/...ad.php?t=42854
A picture of the internals of the set appears in post No.9.

DFWB.

Re: Baird Garrick
 

David,

Darius' reference was to the Fernseh HPE 5R. https://www.earlytelevision.org/fernseh.html

HPE 5 R (1939). Projection set produces a 17" by 20" picture on a directional screen attached to the lid. This set appeared in a 1939 magazine and was identified as being at the 1939 Berlin Exposition. It was to be sold for about $225. It uses Baird's patented vertical deflection. Baird was a member of Fernseh A.G. (Information courtesy of Darius-Karim Mottaghian-Milani).

Peter

Re: Baird Garrick
 

Hi all,
Last night I drew up the circuit of the timebase section of the Baird Garrick as it currently is, with flyback EHT. See the attached PDF.

The focusing arrangement is interesting with a constant current sink which works by comparing the voltage across VR6 with a 100V reference provided by neon stabiliser V1. The grounded grid of the SP42 looks very odd at first.

Also note the DC restoration diode on the CRT grid, however no such diode appears on the cathode circuit. Remember that the black and red wires from the vision receiver provide a negative and a positive video output.

When the set was adapted to flyback EHT, VR4, L3 and C4 were added together with V8 and C17.

I don't know the actual value of wirewound screen feed resistor R8 as it has overheated, loosing all of its outer cement and causing the resistance wire to spring out. I will attempt to measure what is left.

The frame circuit is very similar to the Baird T18.

Cheers
Andy

Re: Baird Garrick
 

Hi all,
in the circuit of the timebase that is in my last post, you can see that the screen feed resistor of the line output valve (R8) is labelled 3K3? The reason why becomes clear when you look at the attached photo of it...

Anyway, you can just make out that the very left hand part of this resistor is still intact. By measuring its resistance and width I was able to extrapolate it. This produced a value in the range of 6K to 8K, so I have ordered a 6K8 14W resistor to try.
It is interesting to note that the screen feed is not decoupled unlike in the Baird Countryman (which is probably where the flyback EHT line output transformer comes from). The pre-war T18 circuit is of no use here either as it uses a triode for the line output.

Cheers
Andy

Re: Baird Garrick
 

Hi all,
I've been re-stuffing the waxies on the underside of the timebase chassis of the Baird. Now I turn my attention to the electrolytics...
The first photo shows a metal bodied electrolytic who's can might have been shorting against the tag next to it. This would be one reason for the burn up in the line output stage. Anyway, it is not original, so I set out to make up a cardboard one copied from others in the set.

I obtained a spare Plessey capacitor of the right size and different value. First I removed the label and pulled off the lead out wires by waggling them until they snapped.
Then (picture 2) I drilled a 0.8mm hole just under the rivet on each end cap.

The capacitor is then sliced open (picture 3) and the insides removed.

A new capacitor is fitted with extended lead out wires which are threaded through the holes that were drilled in the end caps (picture 4).

The end caps were then glued in with UHU, the cut slot was also glued with UHU and a single layer of sellotape was wound round to hold it together whilst the glue set.
The tape was left on, but covered up by covering with a lablel of the correct value which I had made by colour photocopying it from one of the other capacitors in the set (which was also rebuilt).

Finally the capacitor was put back in place of the metal bodied one. You can see this at the top of picture 5. The capacitor that was copied is at the bottom of the picture and the three waxies at the bottom end have also been re-stuffed. Note the burnt out resistor has been replaced with a new one and the damaged wiring re-sleeved.

Cheers
Andy

Re: Baird Garrick
 

Very nice! :)

Peter

Re: Baird Garrick
 

This is the way it's going with the restoration of early TVs and radios. We're do our very best to return the old electronics back to the original appearance. No more horrible Hi-Viz capacitors on show. The only worry of course is if a set was to fall into the hands of someone else who then takes a look at all the old looking components and decides to replace everything we painstakingly replicated. It would be a good idea to keep a service record with every set.

DFWB.

Re: Baird Garrick
 

I have seen masks successfully cut from large pieces of expanded polystyrene (easily obtainable) and the area of the mask that you see is then overlaid and shaped with plaster of paris by scraping and sanding etc. Alternatively - though far less easy - fashion from wood.

Re: Baird Garrick
 

Hi all,
not long to go before power up :)
Here you can see a general view of the vision chassis. Note that the rogue flyback EHT line output transformer has been put back for now.

The waxies on the tube base panel still need rebuilding, felt strips need to be added to the woodwork to cushion the tube, the aquadag earthing needs to be worked out and the new CRT fitted.

Of course a replacement set of valves has been fitted (they were nearly all missing), most of which were NOS. When I opened up the box containing the rare SP42, I found it was from the BBC valve department - I hope they don't want it back ;D

Cheers
Andy

Re: Baird Garrick
 

Hi all,
after re-stuffing the remaining caps on the CRT base board, I thought now might be a good time to power the set up before I fit the CRT.

I lugged the heavy PSU on to the bench and connected it up with the fuse to the mains EHT transformer disconnected.
In the second picture you can see the orange glow of the 100V reference for the focus regulator.
At first there was no line whistle, although there was a very loud noise coming from the frame coils. I swapped the Mazda PEN46 that I had fitted in the frame generator position with the VT127 (PEN46 clone) which I had in the line stage and this time I got line whistle, but no frame noise.
I did wonder if the Rayethon VT127 (which was a NOS WW2 air ministry valve) was no good in a self oscillating output stage. I didn't have a spare Mazda PEN46, but fortunately I did have a spare NOS VT127. Lucklily this one worked ok.
The third photo shows the faulty valve - it looks ok and I was the first person to open the box since it was re-labled with a CV number.

I attached a scope to the feedback winding of the frame output circuit and it showed a nice waveform which had 50Hz nicely in the range of the hold control. Turning up the height seemed to cause a breakdown which turned out to be the spark gap in the x100 scope probe :-[ Notice the size of the flyback pulse on the scope 8-o. Removing the probe enabled me to turn the height control right up. The scope probe survived intact ;D. I wonder how high the anode voltage goes during the frame flyback?

I attached the scope probe across the line coils and got a lovely waveform. Again 10KHz was easily in range of the hold control. I then fed in the test card from an Aurora and was able to lock the timebases. The scope picture shows a nice 10.125KHz locked waveform :)

The HT was 365V.
The flyback EHT was rather low at 4.11KV. Maybe the EY51 is a little tired. However, when the set was first obtained it was noted that there had been a wax leak from the line output transformer. It turns out that the wax from the EHT rectifier's heater winding has gone gooey, so maybe there is an EHT leak there. I must look out an EHT stick and try it.

That's all for now.

Cheers
Andy

Re: Baird Garrick
 

Hi all,
this is the first of a two part update.

I tried an EHT diode in place of the EY51, but still got no more than about 4kV. So I put the EY51 back in circuit.

I used a piece of 35mm waste pipe to ansue that the scan coils and CRT clamp were reasonably in line.

Next I attached some felt strips to the wooden CRT support, together with an aquadag earthing contact.

Next up - fitting the CRT...

Cheers
Andy

Re: Baird Garrick
 

Hi all,
part 2 of 2 of my update.

I installed a NOS CRT. It is an MW31-74 which has a cavity style anode connector and also requires an ion trap magnet. John (Heatercathodeshort) very kindly provided me with an ion trap magnet and a cavity to top cap anode adaptor (see second photo).

I powered up the set and after fiddling with the ion trap magnet, I got a picture of a sort...

The focus is poor due to the low EHT and the line linearity is terrible. I will have a go at trying different screen feed resitor valves for the line output valve when I get the chance; to see if that solves both problems.

Another issue is image cut off slightly on the left-hand side. This is mostly due to the ion trap magnet no quite being in the right place. The fourth picture shows the problem. The magnet ring is behind the focus coil, and it is just below the 10K resistor behind the paxolin panel. It really needs to be nearer the tube base, but if put the other side of the panel it interferes with the solder tags. I need to think about this one...

The last photo shows the CRT guarantee card. Do you think it is still valid?

Cheers
Andy

Re: Baird Garrick
 

Hi Andy,

I wonder if this might be another case of David's magnetised scan yoke and shifting the ion trap to compensate for it is cutting off the beam?

Peter

Re: Baird Garrick
 

Reopened by request
Cheers
Mike T

Re: Baird Garrick
 

Hi everyone,
Mike has kindly reopened this thread because finally the end of this restoration is in sight.

After a long hiatus, the purchase of a suitable rubber mask was the push this project needed to get it going again.
More on this a bit later today I hope.

Cheers
Andy

Re: Baird Garrick
 

Here we go! First of all the story of the mask and another CRT

I recently found a 12" round CRT being advertised for sale online. What was unusual about it, was that it was mounted on a wooden frame, together with part of the front of an old TV and included the CRT mask as well.
I put in an offer and it was accepted. I offered more than an untested 12" CRT, because it was the mask I was really after and I didn't want to miss out on the sale.

A friend helped me collect it from a place near the Cambridge fens, between Cambridge and Peterborough. IT turned out to be amongst the last items being sold by a collector who had to give up his hobby for health reasons. He still kept his favourite sets and it was nice seeing the small collection he had left. Whilst there I was able to buy some vintag components as well.

When I got home I found that the CRT in question was a Mullard MW31-18. Being a straight gun tube, it is a much better replacement for the original MW31-7 in the Baird Garrick other than the MW31-74 that I had fitted. The ion trap magnet of the MW31-74 was really in the way of things. I tested the CRT and it was just into the good area, in fact I was sure it was better than this as the meter on my tester is a bit sticky.

The rubber mask is a much better replacement than the Bush TV24 style mask that I was planning to use. The extra picture width required to fill the 'double D' mask was going to be a problem, the cabinet had no way of mounting the mask and the outer edges of the mask were not wide enough to fill the safety glass.
The newly obtained mask was of the type that holds the safety glass as well. This arrangement ususally causes the mask to deform due to the weight of the glass and this mask was starting suffer in that way. As the Baird Garrick hs the safety glass fixed to the cabinet, I decided to cut off the part of the mask that retains the glass.

More to follow...

BTW, I never did find out what set the CRT came from. The scan coils look a bit PYE like, indeed the mask looks like a larger version of the LV30 mask, rather than a GEC one which has much thinner rubber. The scan coils had a four pin plug on a bit like a Vidor and the focus unit was an off the shelf item. The badge at the front was merely a transfer (now missing), I wondered it if was from a Sobel. Any ideas?

Cheers
Andy

Re: Baird Garrick
 

"BTW, I never did find out what set the CRT came from. The scan coils look a bit PYE like, indeed the mask looks like a larger version of the LV30 mask, rather than a GEC one which has much thinner rubber. The scan coils had a four pin plug on a bit like a Vidor and the focus unit was an off the shelf item. The badge at the front was merely a transfer (now missing), I wondered it if was from a Sobel. Any ideas?"
Hi Andy,
it might be from a Peto-Scott. There's a TV127 chassis and scan coils upstairs and the coils look similar to those on your CRT unit.

DFWB.

Re: Baird Garrick
 

Hi David,
I think you've found it!

Cheers
Andy

Re: Baird Garrick
 

There appears to be very few adverts for Baird receivers especially the Garrick.
You may have seen this one Andy. W.W. November 1948. John.

Re: Baird Garrick
 

Thanks for that John. I have got another copy of it somewhere.
The points listed in the advert are indeed its best points.
The push-pull video drive gives great contrast without flyback lines.
The focus is indeed current regulated.

There is no mention though of the poor picture linearity (no adjustments for that) or that the contrast control is buried deep within the set or of course one of the most lethal mains EHT arrangments that there ever was.

Anyway, back to the restoration.
Folks may remember that the original style line output transformer needed to be recreated. Early on in the restoration I swapped out the smoothing choke in the radio section for another one of a different shape. This gave me the lamminations and bobbin for the line output transformer (they are a very unusual size).
For the original transformer, a split bobbin was used. To achive this I made up a gerber file, using Altium, of the outline of one half of one of the end cheeks. I then used a CNC router to rout two identical end cheek halves. These were then glued to the bobbin with epoxy.

As for turns ratio, wire size and inductance, I knew none of these. I had planned to take some detailed measurements from the restored Lyric set, but Covid restrictions prevented this. So it was trial and error. After serveral iterations, I now have something that works. The primary is much fatter than the original and I could have another go at with thinner wire, but as it works I shall leave it as it is. This transformer is not wavewound. The split bobbing helps lower the capacitance, but also the over sized bobbin allows quite thick wire to be used for the primary which greatly helps to reduce capacitance by producing a fatter coil.
The primary is 1250 turns of 27 SWG and the secondary is 600 turns of 29 SWG. I think that 29 SWG for both windings would have been better.
Anyway, it works quite well. Line linearity is not perfect, but was better than with the tranformer that was in the set when I got it.

More to come...

Cheers
Andy