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Forum 141

Ekco T141

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freya
(@freya)
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I bought this set from ebay with the tube down to air with obvious trauma to the evacuation point, my hope was to find a replacement.A very kind forum member sorted a CRM121A which out for me and it eventually made its way with the T141 and a TU142 down to cornwall.

During the weekend i set about having a look and was amazed to find the chassis was very very clean with no signs of rust and very little dust or dirt.
Looking on the underside of the chassis it was apparent was untouched.
I set about sliding the dud CRM121A tube from its precarious cradle arrangement and refitting the replacement CRM121A.
After snipping the input capacitor i powered up and after only about 15 seconds i had a weird wispy raster moving around the screen accompanied with loud buzzing sound, a new 100uf+60uf capacitor on the main smoother sorted this and i now have this full screen confused testcard.
Where to go next, i dont want to start ripping out all the waxies as the result is so good so far, my guess is start on the little coloured band 0.003uf capacitors in sound and IF strip..

 
Posted : 22/10/2013 7:05 pm
malcscott
(@malcscott)
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A set this age will need all of the wax caps replacing.

 
Posted : 22/10/2013 7:24 pm
freya
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It was my hope to get a testcard up with the minimal components being changed, my usual method is one at a time and see the results however seeing the full frame with good EHT put ideas in my head.

 
Posted : 22/10/2013 7:48 pm
mark pirate
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Changing one cap at a time is a good idea, less chance of a mistake when going for blanket replacement.
As Malc rightly says, all of the caps should be replaced, I would also check the resistors while you are at it.

Looks like you have a good Mazda tube there, I wonder who had it :aaj

 
Posted : 22/10/2013 8:29 pm
freya
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What was odd about the tube was when the set was powered with the faulty smoothers the raster looked like it showed ion burn in the way of a dark round circle about 2 1/2 inches diameter.....but it moved about. I can only conclude it was a reflection in some way of the cathode ?

I may be inclined to remove said capacitors for a photo to show what i mean.

To go on with the set, i changed the 2uf sync coupler and now have this:

 
Posted : 22/10/2013 8:54 pm
freya
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Had a heart stopping moment last night after changing some of the capacitors in the line stage and with the set on and running but raster same as before, there was a bright flash from the rear of the chassis and both fuses had blown, also taking out the circuit breaker.
My fears were immediately for the mains transformer that powers all the heaters, after spending some time last night looking through the rubber wiring that is still very good and no problems found i decided to give it a rest and sleep on it.

This morning in fresh light and taking some measurments it was not looking good, until that is i disconnected the mains switch from the transformer. At this point the short was still evident indicating the problem was between the mains input and the switch. Testing between the terminals proved the switch to be the problem measuring 10k between the live and neutral terminals.
As the switch is so accessible it was removed and opened with the aid of my dremmel. The contacts have been destroyed and much carbon deposited everywhere.

Strapping the switch out and replacing the fuses restored the set to its previous working condition.

 
Posted : 23/10/2013 1:30 pm
unixmanuk
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Wonder if the negative picture is down to a duff vision detector, Stephen?

John

 
Posted : 23/10/2013 2:24 pm
freya
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Not sure, the line is only just locked too.
All capacitors in timebase and frame stages changed now with no change to raster. Next step is into the IF although i hope it is not going to need re alignment :aae

 
Posted : 23/10/2013 2:37 pm
unixmanuk
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May be worth swapping V5 (6D2) and checking associated components, as this is both the vision detector (V5a) and vision interference limiter (V5b). Could try a swap with V13 (sound detector) as a test.
Check the position of the interference limiter switch too. Just a thought...

Does the contrast/brightness setting have any effect?

John

 
Posted : 23/10/2013 3:52 pm
unixmanuk
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One other thing I thought - might the input signal be too high from the Aurora?

As I understand it, the set can be aligned to any of the Band 1 channels, so perhaps this alignment may be slightly out too?

John

 
Posted : 23/10/2013 4:19 pm
freya
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News:
I sat feeling pleased with myself to and the build quality of previously mentioned transformer was great after all.
Next to the capacitor stock ;
Seeing no 3.3nf 0.0033 and only 4 off 4.7nf 0.0047 limited my recapping of the IF stage, i set about carefully removing the legs from one end of the exsisting 0.003 beasties, checking just for capacity with the capacitor tester on the fluke. Still one at a time.
Strangely i only found three that were miles out and one with no capacity so i changed those and checked again.

Just out of curiosity i checked the wax capacitors removed from line and frame stages, with the exception of the sync capacitor they were all perfect upto 500 volts, the sync capacitor started breaking down at 200 volts

 
Posted : 23/10/2013 4:32 pm
unixmanuk
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Result!

Nice picture, Stephen, tube looks good too. Well done - easier than I'd expected. :thumb

John

 
Posted : 23/10/2013 4:49 pm
Lloyd
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That picture looks really good, well done!

I always thought Ekco's mains transformers were pretty good, I've got a number of their radio's, and only 1 has a duff transformer. Well, I think it's a dud, it reads really low on the primary, and lights a 100w bulb brightly. I don't dare try it on full mains just in case it goes with a bang!

Lloyd.

 
Posted : 23/10/2013 7:26 pm
Brian Cuff
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That looks great, Stephen. Well done. :aap

Forum Memorial

 
Posted : 23/10/2013 7:33 pm
mark pirate
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That has come up really nicely, you were very lucky to find such a good tube for the set. I have a couple of sets in the collection I would love to get working, but both have duff Mazda tubes :aai

 
Posted : 24/10/2013 10:02 am
IJK2008
(@ijk2008)
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I agree with all comments. You have obtained a great result there.

I have an Ekco TS114 to do and after seeing your results I think it is time I started it!

Cheers

Ian

 
Posted : 25/10/2013 5:33 pm
Till Eulenspiegel
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The Ekco TC138 I picked up in Wales is electrically similar to the T141. Brian's mighty TSC1113 is also similar except that it has a 10KV mains derived EHT system. Has a switched radio tuner.
The original model, the TS88 was a TRF made in London and Birmingham versions. TS105 looks like the TS88 except it has radio.
The 100pF capacitor in the line oscillator can fail. It is in a Miller integrator circuit.
Ekco's third post-war chassis. Second if you discount the TSC30 which was in essence a pre-war model.

Till Eulenspiegel.

 
Posted : 25/10/2013 9:50 pm
freya
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Hi Till, if you would like a copy of the genuine Ekco sheet for the TC138 i have it.

 
Posted : 25/10/2013 9:59 pm
Till Eulenspiegel
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Hi Steven,
Many thanks, the service info will help me greatly. The TV138 is in the workshop awaiting restoration.
I'll post a picture of it shortly when I return to the shop.

Till Eulenspiegel.

 
Posted : 25/10/2013 10:18 pm
Till Eulenspiegel
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Pictures of the Ekco TC138.

Till Eulenspiegel.

 
Posted : 26/10/2013 12:06 am
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