21st Apr 2018, 9:12 am | #81 |
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Re: First TV Project - Ekco TCG316 - Any Advice Appreciated
I am still not happy with the condition of the LOPT and this must be eliminated.
The only way to do this takes some care. I would suggest you remove the screening can around the LOPT. Take a note of the connections, there are only a few. Remove the self tapping securing screw and remove the transformer. DO NOT CLEAN IT! With a hot iron, applied to the EHT anti corona cap on the LOPT remove the anode 'ring' connection from the cup. Now this is where the care bit is important. Unsolder the overwind output lead from cup from beneath and very gently ease it free from the cup. It is a thin wire but with care it will unsolder easily. For the next part you may find it of help here to extend the few leads from the LOPT so that you can stand it beside the chassis. No need to connect the EHT lead at this point. Switch on and see if there is a lively spark from the EHT overwind connection wire that you have unsoldered and isolated from the case. If everything has livened up the case is conductive and you will have to fabricate a replacement from sheet Paxolin, Perspex or a spare plastic translucent ceiling tile. If it does liven up you can plug the U26 back into it's holder leaving the anode connection free. If all is well it should light up. It's very difficult when we are not 'hands on' and I suspect the guys on this thread would have had a result in 20 mins if this had been possible. I'm sure we will end up with a good result but as you can imagine you can't learn all of the tricks of the trade with one chassis. Let us know the results. John. |
21st Apr 2018, 10:35 am | #82 |
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Re: First TV Project - Ekco TCG316 - Any Advice Appreciated
I dragged this Ekco T331 from the depths of the earth this morning. It has an almost identical chassis to your TCG.
The pictures show the size of spark obtained when an insulated screwdriver is brushed across the 30P4 top cap. It is quite small. The screwdriver when brought close to the U25/26 anode produces a very lively 1/4" spark. The LOPT in this particular chassis is the early version with wired in EHT rectifier type U25. Other than that the LOPTs are identical. Just use a plastic handled tool for the test. It is quite safe but do not short the blade to chassis. As mentioned the 'plastic' case is a weak point with all Ekco models from the T221 through the 300 series. The windings themselves are very reliable and I have never known these to be faulty and believe me I have serviced many of these Ekco chassis. The pictures give some idea of the sparks that should be obtained and the excellent picture obtainable when all is correct. John. |
21st Apr 2018, 12:12 pm | #83 |
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Re: First TV Project - Ekco TCG316 - Any Advice Appreciated
This is a fascinating thread. I get very tempted to buy a set to restore but have been put off by the EHT and finding space for the set. I will continue to follow this with interest.
I think that John's comment about experienced restorers being able to find faults quickly is very relevant. It would be great to be in a workshop with experienced technicians there and to be able to ask quick questions as you proceed.
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21st Apr 2018, 3:22 pm | #84 |
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Re: First TV Project - Ekco TCG316 - Any Advice Appreciated
Thanks for the advice, Nick and John
I tried testing for a spark with an insulated screwdriver and as you would have guessed, hardly anything. I have to basically touch on the EHT anode to get a tiny speck of light, no fat spark just a minuscule dot of light. Touching the anode of the 30P4 gives even worse results, again, I have to essentially contact the screwdriver on the anode cap and only then if you're in pitch black and leaning in really close can you see the smallest speck of light possible! I'll go over the LOPT and scan coil connections against the diagram and see if I find anything unusual. I still don't know where that loose wire goes that I mentioned earlier connected to R92 Before I touch the LOPT, I'm a little confused at the way you described what to do with it, my fault not yours! I made a quick sketch of what I think you mean, is it correct? I don't really know what the anti-corona cap looks like either haha Peter |
21st Apr 2018, 3:57 pm | #85 | |
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Re: First TV Project - Ekco TCG316 - Any Advice Appreciated
Quote:
I suspect that piece of wire has fractured off either the linearity coil or the width coil. Study this area carefully. Check the connections to both the width & lin coils. Good luck! Nick |
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21st Apr 2018, 5:00 pm | #86 |
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Re: First TV Project - Ekco TCG316 - Any Advice Appreciated
I believe the loose wire did in fact come off the width coil, will probably be a nightmare to get it soldered back in place
As the the LOPT, I have it removed and noticed the smaller winding is a loose rattle fit around the core, I know it doesn't really matter because it works on induction but should the winding go over that rubber sleeve and be a bit more of a snug fit? Also it you look on the top you will notice a few hairline cracks when the light is shining at the right angle. The EHT cable worked its way off the tube socket and I'll get it soldered back in situ. |
21st Apr 2018, 6:22 pm | #87 |
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Re: First TV Project - Ekco TCG316 - Any Advice Appreciated
All set up and tested, Heath Robinson eat your heart out.
Unfortunately I'm still getting a minuscule dot of light instead of a healthy spark... https://youtu.be/UpAJyUNUn5s |
21st Apr 2018, 7:55 pm | #88 |
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Re: First TV Project - Ekco TCG316 - Any Advice Appreciated
Hi Peter,
Have you attended to the broken wire on the width coil? With the wire broken, in effect it means that one of the line coils is not connected. This will have a significant effect on the operation of the line O/P stage. In one of your earlier pictures, the winding with two turns powers the heater of the U26. It won't matter where this is positioned or that it is a loose fit on the plastic former. Cheers Nick |
21st Apr 2018, 8:38 pm | #89 |
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Re: First TV Project - Ekco TCG316 - Any Advice Appreciated
Funny you should say that Nick! It's what I've been doing for the past 2 hours. The thin wire had snapped right inside the coil so I had to do a bit of open heart surgery, took quite a bit of finding! It's a bit of a bodge and I don't even know if it will work again but I couldn't think of anything else.
Peter |
21st Apr 2018, 8:41 pm | #90 |
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Re: First TV Project - Ekco TCG316 - Any Advice Appreciated
Well done for persevering, I had wondered if it was the inside end that had broken away.
Fingers crossed for improvement on the EHT now.
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21st Apr 2018, 8:58 pm | #91 |
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Re: First TV Project - Ekco TCG316 - Any Advice Appreciated
I don't think it's good news though, I'm not getting any continuity in that part of the coil, I'm certain I soldered it correctly, maybe all that verdigris on the coil has something to do with it...
Edit: I think the coil's a dud, I opened it up and re-soldered it just to be sure but it's still not passing the continuity test. Last edited by Vakito227; 21st Apr 2018 at 9:23 pm. |
21st Apr 2018, 9:38 pm | #92 |
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Re: First TV Project - Ekco TCG316 - Any Advice Appreciated
Not so much green spot corrosion, more like green splat.
A post in the wanted section may turn something up, I don't have any scrap chassis with that coil unfortunately. I think you could bypass it for test purposes, short term.
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Stephen _________"It`s only an old telly" ___ |
21st Apr 2018, 9:49 pm | #93 |
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Re: First TV Project - Ekco TCG316 - Any Advice Appreciated
Yeah I could give the wanted page a whirl. What I'll do is if I find out the plastic case for the LOPT is no good, I can post them both on the same thread, I'm also in need of a new channel selector ring I think the previous owners have ran their thumbs over it when changing channels and rubbed all the lettering off!
Peter |
22nd Apr 2018, 9:00 am | #94 |
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Re: First TV Project - Ekco TCG316 - Any Advice Appreciated
Your sketch is correct Peter. The Anti Corona solder cup is the circular terminal on the transformer case connecting the fine wire from the overwind to the U26.
I would hold off this test until you get that width coil sorted. That will have a dramatic effect on the operation of the line output stage. It's a rare failure. I will have a look through my junk, you never know! If the case is dragging it down when you have sorted the width coil it is not difficult to construct one from insulated sheet. Just three straight pieces are required cut to size. John. |
22nd Apr 2018, 3:39 pm | #95 |
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Re: First TV Project - Ekco TCG316 - Any Advice Appreciated
I have managed to find a width coil [two windings]for the Ekco TMB272. It is very similar to the one you require and should do the job.
Please PM me with your details and I will arrange to post FOC. Take care when fitting it. It has lead out wires that can be damaged with heavy handling. John. |
25th Apr 2018, 7:01 pm | #96 |
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Re: First TV Project - Ekco TCG316 - Any Advice Appreciated
Big thanks to John for the new coil, fitted without problem although it was more stressful than eye surgery!
The continuity tests good now on both windings and I'll have another go at powering it up once I finish my non-television related jobs Peter |
25th Apr 2018, 7:11 pm | #97 |
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Re: First TV Project - Ekco TCG316 - Any Advice Appreciated
The forum comes up trumps again, well done John, Peter and fingers crossed again for the next power up.
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25th Apr 2018, 8:03 pm | #98 |
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Re: First TV Project - Ekco TCG316 - Any Advice Appreciated
....nope! I think the new coil has cured A problem but not THE problem.
However I did catch the U191 valve trying to cremate itself, I'm unsure whether it was caused by the new coil (Unlikely) or me just being unobservant the previous times (Very Likely). Perhaps it can give us some leads though, optimism is key. Peter |
25th Apr 2018, 8:47 pm | #99 |
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Re: First TV Project - Ekco TCG316 - Any Advice Appreciated
OUCH!!
Looks like the poor U191 is conducting the entire HT current straight down to chassis! I suspect you have a short somewhere! Are you sure you have wired the width coil into the correct places? With the set switched OFF, measure the resistance from the top cap of the U191 to chassis with your meter set to ohms. It should be at least 150K Ohms looking at the circuit. If it's very much less, you need to find out why. If the reading is 150K or more, the problem is elsewhere. Good luck Nick |
25th Apr 2018, 8:56 pm | #100 |
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Re: First TV Project - Ekco TCG316 - Any Advice Appreciated
I remember this fault, it was quite common. The insulation of the width coil breaks down and short circuits to the metalwork.
DFWB. |