2 duds and a repair

[Mikey405]

Hi everyone. I thought I ought to write up the exploits of a weekend spent not getting very far and then a remarkable restoration – although remarkable in a quite unremarkable way.

A couple of weekends ago my pal Tone turned up at the door demanding admittance to have a go at sorting out some of the old junk that I hadn’t got round to fixing in years (which is most of my stuff to be honest). Against a background of my plaintive whingeing, a suitable set was extricated from the back room, a Pye VT2. The set was duly dumped onto the workbench and work began. In true John-Wakely style we plugged the beast into full mains almost immediately and turned on. There were heaters and no sizzling noises or loud bangs, which was good enough for Tone. Unfortunately after a few minutes there was also no line whistle. A very quick prod around with the voltmeter revealed no screen grid supply to the PL81 combined line oscillator and output valve. The HT was good and the 5.6K feed resistor was okay so this could only mean one thing – The line oscillator transformer was open circuit. Damn. So, after a mere 20 minutes of prodding, the set was carted back to the stock room and another set was selected for a day of tele-fiddling.

This time a nice little Ekco T161 was selected as being a suitable candidate. As Tone allegedly did his back in some time during the early 1980s, he was far too fragile to help with moving the Ekco and I was left to struggle with the set over the assault-course of magazines, components, valves and all manner of other detritus littering my hall and into the workshop. I was quite shocked at how heavy the set felt in my ancient old age; I’m sure I’m nowhere near as strong as I was a few years back – I’d have thought a little 12 inch Ekco a pretty light affair in my thirties but now I’m in my forties I struggle lifting anything much heavier than a mobile phone. Anyway, the back removed and with Tone now gaily blowing clouds of dust out of the back of the set into my coffee, the next restoration was started in earnest. Once again power was applied in a manly fashion by plugging the set in without any thought to reforming anything, least of all the delicate smoothing and reservoir caps, and once again the valves all lit up, but, once again, no picture appeared - although this time we had some semblance of EHT at the top cap. Although we had no picture, turning the set off revealed a brief image of the cathode – or what was left of it – on the CRT face. The tube, one of Mazda’s finest 12-inch triodes, showed a brief dull circular outline of the cathode surface on the screen without the slightest hint of anything left in the middle with which to emit electrons. Connecting the tube to the workshop's trusty B and K tube tester with a set of croc-clips revealed the full glory of the emissive surface – or lack thereof. The needle stayed very firmly on the “zero” line and attempts to bop the poor old thing into life provided no tangible results whatsoever. So the set went back on the “AP” pile and a third set was brought out for attention.

This time it was a little Baird T163 or, as the service manual would have it, a Scophony-Baird Portable Televisor. This was a fair bit lighter and easier to man-handle into the workshop on my own. First thing first was to work out how the back (or rather the front) was removed. Bairds of this period always seem to like using rather obviously-placed screws in locations where no other manufacturers would dream of putting them - in the middle of the top of the cabinet for instance – A shame really as the cabinets always seem to be the best bits. Any-who, the front removed and the chassis somewhat begrudgingly slid out of the cabinet on a set of bent and flimsy aluminium slide-rails, we started work for a third time. This time I put my foot down and insisted that the HT capacitors were reformed as the set looked as though it was a bit more interesting than the other two common-or-garden models. Tone, being made of sterner stuff than me, didn’t really like the idea but whilst he was outside smoking his pipe I connected up my death-trap capacitor reformer and gave the smoother and resevoir a quick once-over before disconnecting the thing quickly and hiding it away again when I heard Tone’s footsteps approaching. I pretended I’d been struggling to replace the dropper resistor instead as the door opened – which actually turned out to be the case with the nasty ancient high-melting-point solder proving almost impossible to remove. These sets are very simple affairs really and quite odd in their design and I wasn’t expecting great things from the set with its flat-face 9 inch GEC 6506A triode tube, so - I was quite astonished that the first time I switched the dear little thing on, a picture appeared. Excitedly plugging in the Aurora and twiddling the brightness / contrast controls showed a bright, fully-scanned perfectly-linear picture, although it did have a bit of “cogging” on the test card image. Diving in to the circuit revealed that the sync-coupling cap had been previously replaced in the 1960s (at a guess) with one of those RS plastic blue 0.1uF caps that BRC seemed to love so much in their monochrome sets. The cap was removed with some difficulty – all the solder in the set just crystallised as it melted and made everything very awkward to unsolder – and I managed to pull the end off of one of the wax caps in another part of the circuit, so that had to be replaced at the same time (along with a resistor which was wrapped around it and a second resistor which I also skilfully managed to snap in the process of removing the original cap).

Having replaced the sync-coupling cap (and the three other components damaged in the process), the set was powered up again. This time we had a bright, fully-scanned, perfectly linear picture and lovely boomy sound from the speaker - all from replacing 5 components (and probably just two components had I not been so clumsy).

And so that was it. As the picture hadn’t budged after an hour of running it was decided to box the set up and treat it as a “repair” as opposed to a “restoration” and leave all the wax caps until they actually warranted changing. The photos below show the picture produced by the set and some of the Baird’s peculiarities. The first picture shows a bit of an oddity of the Baird circuit which is a PL36 being used in the self-oscillating FRAME stage – It’s supposed to be a KT36 (the same as the line stage) but it has been modified some time in its life and a PL36 now resides there. (The valve on the right of the picture.) Another oddity here is that there is no voltage adjustment for the HT – The valve heaters tapping can be adjusted but the HT just gets whatever it’s given. The second picture is of a tiny amount of dust burning off the dropper, and the third picture is of the set working as it was the first time the sync coupling cap was replaced. The height and width in the last picture appear too narrow but the original 5:4 rubber mask was completely melted so an Ekco TMB272 4:3 mask was expertly sellotaped in its place. There is no width control to compensate for the Ekco’s double-D mask so the height has also been reduced to keep the picture roughly the correct aspect-ratio. The slight pincushion distortion is, I believe, a feature of the set and its peculiar pre-war-esque DC-frame-shift electromagnets around the sides of the tube neck.

And that’s it. Thanks for reading everyone.

Kind regards.

From Mike.
PS. If anyone has a line-oscillator coil from a Pye V2 or a Pye VT2 (or a CRM121 tube) then I can write up the other two sets as well.

[line sync]

Great stuff mike , I enjoyed reading that.
I love the picture of the smoking chassis and whats with the corned beef tin ?

Robin

[Radio Wrangler]

Originally Posted by Mikey405

I was quite shocked at how heavy the set felt in my ancient old age; I’m sure I’m nowhere near as strong as I was a few years back – I’d have thought a little 12 inch Ekco a pretty light affair in my thirties but now I’m in my forties I struggle lifting anything much heavier than a mobile phone.

It's not a linear progression, Mike. Those in their teens and twenties seem completely unable to lift anything other than a mobile phone...

David

[mark pirate]

Nice job on the Baird Mike
I have the later T164, quirky little thing but sadly let down by a flat CRM92.

whats with the corned beef tin ?

It certainly does not appear to be a condenser, unless Fray Bentos have moved in to electrical components

Mark

[beery]

Hi Mikey,
Great stuff, but I'm not sure that the corned beef tin is at all right. I think you should be using a tin of Carnation Condensered milk!
I'll get my coat...

Andy

[Herald1360]

There's wires going into it in the bottom left of picture 4 and a ground soldered to the top.

Maybe Corned Beef Dubilier is an offshoot of Corning-Dubilier?

[Mikey405]

Thanks for the kind comments everyone.

The Dubilier corned-beef-condenser was, of course, only fitted to fringe models so is not often seen in TVs of this age. And if it ever goes wrong then it can be re-stuffed easily using the little key on the side of the tin.

[Heatercathodeshort]

Originally Posted by mark pirate

I have the later T164, quirky little thing but sadly let down by a flat CRM92.Mark

Interesting Mark. The T164 is the big brother of the T161 with a 15" either CRM152B or 153 Mazda CRT, both equally iffy... Maybe you have the shrunken head model. John.

[Mikey405]

Isn't the T164 the little 9" portable set which looks like a small "Townsman" with the same curved slot in each side and a picture of JLB on the front John?

[mark pirate]

You are correct Mike, I think John is thinking of a different model. (see below)

Mark

[beery]

I think the confusion might be between Baird and Ekco...

Cheers
Andy

[Heatercathodeshort]

Yes Mike, you are correct. It was the Ekco T161 that took my attention. Any mention of an Ekco usually locks me into tunnel vision. I just can't get any enthusiasm for post war Bairds... John.