The Ekco is a 7" CRT vision only TV receiver designed as a low cost entry model. The audio from the demodulator can be connected to the pick-up terminals of a radio receiver.
Earlier this year when the set was unattended the timebase mains transformer burnt out filling the room with black smoke. Mike Barker rewound the transformer to exactly the same specification and appearance of the original part.
Failure of the transformer can be attributed to the 8mfd reservoir capacitor having gone short circuit. The Mazda UU5 HT rectifier was also destroyed.
Work done so far is clean up the mess on the chassis and fit a replacement reservoir capacitor. The mains transformer will be fitted tomorrow.
There's evidence of sloppy 1990s repair work has been done to this set. Again, such work doesn't look right in a rare TV set made in 1938.
For a set designed to sell for a reasonable price it could be said it is a rather over-engineered receiver, for example three mains transformers!
Geordie McBoyne.
If that last pic is of Mike Barkers rewind job, I must congratulate him on superb workmanship.
That is indeed a nicely done rebuild.
Joe
Hi
Mike indeed does a superb job Joe, don't expect it to be returned in a hurry though.
The little Ekco is a lovely little set, I remember David bringing it here many years ago at one of my Scottish meets.
(17-07-2023, 07:13 AM)Murphyv310 Wrote: [ -> ]Hi
The little Ekco is a lovely little set, I remember David bringing it here many years ago at one of my Scottish meets.
Trevor,
Are you thinking of the same set?
I remember David bringing this one. Incredibly heavily built but worked well
[
attachment=22070]
Peter
Trevor,
I have been rewinding and making transformers for more than 50 years.
Dad taught me. SMALL transformers, not power distribution, but I do know about them.
I know nothing about TV anymore ( I have never really been interested in the first place ),
and my current TV is a computer. Analogue TV disappeared from Australia years ago.
I did cut my teeth and learn my valve theory way back in time when black and white was the ONLY TV standard available.
I mostly watch my computer TV on youtube, apart from the ABC news.
I do pay a couple of movie channels for the wife to watch.
So, to dissmantle, count and analyse the layer configuration of even the simplest transformer is not easy.
IF its been burnt ( overloaded ) its even worse and very messy.
If its Quad style, potted in bitumen, its a truly horrible job.
For some reason, that bitumen ends up on the car 200 yards away from the rewind area,
without having any contact with the car. ????
Then calculate the gauges, insulating layers, ( and old english traffos could be particularly frenetic in construction )
Layering, and then waxing ( common ) bitumen dipping, ( average cheap traffo ) varnish dipping without vacuum , then the hardest of all, vacuum impregnated,
then baked.
There are also PCB ( polychlorinated biphenyls ) filled mil spec stuff left over from some previous time, and in big stuff, oil filled.
ALL very tedius for anybody that has done it. Its NOT very inspiring.
Just my observation Trevor.
Joe
(17-07-2023, 09:03 AM)peter scott Wrote: [ -> ] (17-07-2023, 07:13 AM)Murphyv310 Wrote: [ -> ]Hi
The little Ekco is a lovely little set, I remember David bringing it here many years ago at one of my Scottish meets.
Trevor,
Are you thinking of the same set?
I remember David bringing this one. Incredibly heavily built but worked well
Peter
Hi Peter.
Indeed you are correct, David had brought the version with sound. I did see the vision only one on a visit to David a number of years ago.
The replacement mains transformer has been fully wired into the circuit. A Mazda UU4 HT rectifier fitted. Time to apply full mains to the receiver. Took quite a while for something to appear on the screen, the Mazda U21 EHT rectifier is of the slow warm-up type. As can be seen from the attached pictures the frame timebase needs attention. The T41 gas thyratron and PEN45 valves are OK so some serious fault finding is called for.
The Mazda CRM71 is excellent.
Interesting to note that this made in 1938 TV set has a standard Belling-Lee aerial socket.
Geordie McBoyne.
No ion or switch-off burn! (I have difficulty sometimes telling the difference). Didn't thyratrons in timebases have a reputation for jitter?
Steve
Hi Steve,
those Mazda T41 thyratrons are prone to erratic performance, sometimes you can get away with swopping the line and frame T41s around, but replacement is the only answer.
The timebase circuits and components in the TA201 continued to be employed in Ekco TV sets as late as 1948, models TS46, TSC93 etc.
The 6.3volt version, the 6K25 seems to be more reliable. Employed in the ViewMaster TV set.
This afternoon I will attempt to coax the frame timebase to generate more vertical scan.
Geordie McBoyne.