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Ekco T311 (was: CRT substitution?)

 
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Ekco T311 (was: CRT substitution?)

Post by Till Eulenspiegel » Wed Jan 20, 2016 1:39 am

Later production line output transformers were supplied with the U26 instead of the soldered in U25.
This helped to stop of the degeneration of the perspex transformer housing.
What range of valves has your set? Earlier 17" sets have split heater chains consisting of 0.1amp and 0.2amp heater valves. The heater chains merge to a single 0.3 amp chain which consists of the CRT heater and the tuner valves.
From 1956 on Ekco sets used a single 0.3amp heater chain just like almost every other TV manufacturer.

The set is well worth preserving. There is not all that many of this type of set left in existence . It can always be passed on to another collector when you get tired of it.

Till Eulenspiegel.

 
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Re: CRT substitution?

Post by marc » Wed Jan 20, 2016 1:45 am

Just checked both of my TMB272's and the one with the earlier serial number has a U25 and the other set has the U26, both sets appear to have their original LOPT's.
So along with Till's info maybe your set is original with the U26. :aaq

 
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Re: CRT substitution?

Post by Cathovisor » Wed Jan 20, 2016 1:48 am

All being well, I might wrap up well (although TBH it's not that cold here at the moment) and take the set apart tomorrow to clean it and douse the cabinet with woodworm killer. Then we'll find out a bit more about the internals.

 
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Re: CRT substitution?

Post by sideband » Wed Jan 20, 2016 12:23 pm

marc wrote:So along with Till's info maybe your set is original with the U26. :aaq


They (Ekco) tended to use either. My old T283 had a U26 (B9A) reccy but the slightly later T310 (which we had as a main set) had a U25 (wire-ended). Seeing as the T310 and T311 are essentially the same set it seems that either were used. Perhaps the U26 was a later change to help preserve the casing of the LOPT.....

 
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Re: CRT substitution?

Post by marc » Wed Jan 20, 2016 1:09 pm

sideband wrote:Perhaps the U26 was a later change to help preserve the casing of the LOPT.....

Yet ironically with all my Ekco/Dynatron sets past and present it's the ones fitted with U26 that have rotted housings and U25 fitted LOPTs have been fine.... :aab
That reminds me, I must get hold of some perspex to replace the housing on my T344 :aaq

Marc.

 
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Re: CRT substitution?

Post by Cathovisor » Wed Jan 20, 2016 3:01 pm

Lovely day outside today, so a few photos of the chassis:
T311_dusty.jpg
The chassis before cleaning.
T311_under.jpg
An under-chassis view.
T311_lopt.jpg
The LOPT.
The EHT wiring keeps falling off everywhere!

 
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Re: CRT substitution?

Post by Till Eulenspiegel » Wed Jan 20, 2016 4:11 pm

It's the later chassis equipped with valves that have 0.3amp heaters.
The under chassis view clearly shows the extra ballast resistor which is connected across the HT supply when the set is switched to FM radio. When switched to radio the timebase valves are switched off and the 2200ohm resistor introduced into the circuit. Not very green but that's how they did things in those times.

Till Eulenspiegel.

 
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Re: CRT substitution?

Post by nuvistor » Wed Jan 20, 2016 5:30 pm

I don't remember much about them but I did repair them at one time. Apart from the LOPTX disintegrating thats about it, there must have been other faults I fixed but too long ago.
That LOPTX looks in very good condition.

Looking at the chassis, it appears to be in two pieces screwed or riveted together, I wonder if the were two seperate assembly lines working on the Timebase and Signal sections and brought together for final Assy?
Frank

 
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Re: Ekco T311 (was: CRT substitution?)

Post by Cathovisor » Wed Jan 20, 2016 6:40 pm

Some more photos.
T311_clean.jpg
The chassis after hoovering and a bit of white spirit.
T311_ready_for_Christmas.jpg
Date stamp on chassis (cabinet's a day earlier):
did it get to the shops for Christmas?
T311_foam_cleaner.jpg
That looks a bit less filthy!

The main smoothing electrolytic is a type that I have some relatively NOS (made in 1980s) ones of that have been reformed recently (about three months ago) and even have clear plastic sleeves, so that's good: the cabinet is now outside and under cover, well doused in woodworm killer and all the holes have been injected too. The chassis is in the car at the moment!

The polythene surround for the side panel has distorted somewhat so I think I'll be attacking that with a hot-air gun to get it to resettle in a more sensible position.

I'm at a loss what the enormous VDR across the EHT was for.

I think this set might be an interesting exercise...

 
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Re: Ekco T311 (was: CRT substitution?)

Post by marc » Wed Jan 20, 2016 6:48 pm

Cathovisor wrote:I think this set might be an interesting exercise...

I'm pleased to hear that Catho, I would like to see this set done and working especially with the tube substitution. :)
The chassis certainly looks better now too :aad

Marc.

 
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Re: Ekco T311 (was: CRT substitution?)

Post by nuvistor » Wed Jan 20, 2016 7:28 pm

The enormous VDR would probably be a Metrosil, help EHT stability. They used to disintegrate if I remember correctly, don't remember changing one, seemed to work ok without, or at least well enough for the customer not wanting to pay for another.

Frank

 
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Re: Ekco T311 (was: CRT substitution?)

Post by sideband » Wed Jan 20, 2016 8:40 pm

Yes it's a metrosil. They used to fall to bits. Never bothered to replace them and the EHT stability didn't seem too bad. By the time I started in the Trade, these sets were getting on for 15 years old so maybe the flatish tubes compensated for the poorer EHT regulation.....

 
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Re: Ekco T311 (was: CRT substitution?)

Post by Katie Bush » Thu Jan 21, 2016 12:44 am

Ahaa....

1957... Same year as my Dynatron TV34 (and me!).. I'm inclined to believe it's the same chassis in that case, even down to the front control knobs and the FM radio feature.. Visually, it looks the same, and the only difference that stands out is the control triplet panel.. On the Dynatron, those controls are arranged in a neat row of three 'edge' controls between the two main front control clusters.. On this chassis, they're the usual EKCO style side mounted (hidden) triad.

The Dynatron TV34 also used a U26 for the EHT rectifier, ex-works, and I'd surmise the EKCO did likewise.

Once you reach first light, I'd bet on the majority of faults being in the frame linearity, and possibly an issue with the Contrast control, moreover, a constant need to readjust the contrast setting as the set warms up, and potentially, no sound or picture at next switch on (unless you readjust the contrast control again, and do the same routine as the set warms up) I have yet to investigate mine.

If you find the picture doing a crazy sideways twitch on bright scenes, that's were the Metrosil will need attention.. My Dynatron still has its original rod type.. The LOP stage will also make a characteristic 'chip-chip-chip-chip' sound in time with the twitch.. Reducing the contrast can stop the twitch, but obviously, the picture will look flat as a pancake.

The picture quality is superlative, once the set is fully up and running - lovely.... :aad

Dynatron CRT heater volts also = 12.6V nominal.

Marion

 
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Re: Ekco T311 (was: CRT substitution?)

Post by sideband » Thu Jan 21, 2016 11:02 am

Katie Bush wrote:The picture quality is superlative, once the set is fully up and running - lovely.... :aad


The 311 (and the 310) have virtually the same chassis as the earlier T283 (that had a round CRT CRM141) so I would expect this 311 to give the same superb picture as the 283. It was by far the best B/W picture I saw on any set (possibly only exceeded by certain Murphy models).

 
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Re: Ekco T311 (was: CRT substitution?)

Post by Cathovisor » Thu Jan 21, 2016 1:45 pm

Well, good news for this telly; a kind anonymous benefactor has donated a CRM172 to the cause, so it'll be going with the original type of tube :)

 
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Re: Ekco T311 (was: CRT substitution?)

Post by nuvistor » Thu Jan 21, 2016 3:45 pm

Look forward to seeing it working, Ekco/Ferranti provided my bread and butter for quite a few years, always a soft spot for them.

My radios, few that they are mainly Ekco/Ferranti just one Pye, all 50/60's. Must get around to checking the transistor radio I have , not sure if it is Ekco or Ferranti.
Frank


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