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Old 15th Nov 2016, 11:36 am   #41
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Default Re: Ekco T344

Hi LLoyd

I found the 0.1uf on the other end of the width adjustment resistor chain causing the width failing. The strange thing is that neither on the Ekco service sheet or the ERT sheet is this mentioned, the capacitor is simply not on the circuit. I managed to replace this very awkward positioned component without taking the tube out. Now the width is not shrinking I find that although a fairly decent picture is there on the screen it seems to take a lot longer to appear and at first the frame hold is a bit unstable the set warms and there the picture is.

bit more to do to it yet

Ken
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Old 15th Nov 2016, 11:46 am   #42
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Default Re: Ekco T344

Hi Ken.

Glad that bit's sorted, have included the Ekco component layout sheet to see if it's shown there.
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Last edited by Freya; 15th Nov 2016 at 11:56 am. Reason: info changed and added
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Old 15th Nov 2016, 5:49 pm   #43
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Default Re: Ekco T344

Thanks for that Stephen, An odd problem has now developed, some of the heaters are not lit and that also applies to the tube. I cant understand why, as all the heaters are in series.

The question is where do I go from here

Ken
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Old 15th Nov 2016, 5:54 pm   #44
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Default Re: Ekco T344

Are the heaters brighter than normal, look for shorts to chassis on the heater line. Check which valve is the last in the chain to light up and the short will be around that area. Could even be the valve.
I don't think set has two heater chains but could be wrong.
Frank
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Old 15th Nov 2016, 6:01 pm   #45
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Default Re: Ekco T344

It might be a decoupler gone short. Or a valve, but thats less likley.

There are only a few candidates
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Old 15th Nov 2016, 7:55 pm   #46
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Default Re: Ekco T344

Hi Stephen

I took a look at the way in how the heaters were wired in relation to the mains dropper and sectioned the series circuit off by taking a valve out and checking continuity wise and it seems all the heaters are ok in this respect. It looks like I may have to take the tube out to gain access to all of the decoupling capacitors along the heater chain. One thing that puzzles me is why all of a sudden these have played up. Its not gonna be easy to do unless there is a quick method of finding the culprit

Regards

ken
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Old 15th Nov 2016, 10:35 pm   #47
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Default Re: Ekco T344

Re post 44 and 45 with the diagram. Find the last in the chain to light up, the fault has to between that valve and the next one in the chain.
Decoupling cap is favourite as Freya says and also as he says there are only a few candidates.
Frank
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Old 16th Nov 2016, 12:30 pm   #48
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Default Re: Ekco T344

Hi frank

Found the culprit, it was a lump of solder that had fallen in between the valve bases, not sure where it came from but now just got to sort out the frame time base and re build the shroud for the LOPT.

Getting there, slow but sure, more to follow.

Ken
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Old 16th Nov 2016, 12:51 pm   #49
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Default Re: Ekco T344

Excellent, if there was one piece of solder it's possible someone has been there before, worth a quick look around for any more, only a few minutes of a job but may save problems later.
Frank
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Old 17th Nov 2016, 3:20 pm   #50
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Default Re: Ekco T344

Hi Frank

Yes, how true you are, that little piece of solder had sent me on a goose chase, I will check though to see if any more droplets of solder might be lurkin. In the meantime, I found several resistors which were all around the line and frame timebase area had gone really high from their stated values.

At the moment, I have a fairly good picture but with the width adjustment on it's minimum the width is slightly out as I can not see the castellation's which are on each side of the test card. Bit more work to find out why.

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Ken
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Old 17th Nov 2016, 4:19 pm   #51
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Default Re: Ekco T344

Hi Ken,

Its normal for this 100 degree tube to be over scanned and not see the side castellation's.

But, check the special HT boost tap which may have been moved in the past to attempt compensation for the previous width problem.

this is done using the R and B tap, for 230 volts mains R needs to be on 5, and B needs to be on 6.
for 240 volts R is on 6 and B is on 7

Hope this is helpful.
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Old 17th Nov 2016, 5:44 pm   #52
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Default Re: Ekco T344

Hello Stephen,

Thank you for that information on the picture width, and the settings on the Boost Tap, I hadn't realised the a couple of the tappings on the mains dropper were related to this. I have checked this and these are as they should be for our current mains voltage. The odd thing is although UK Power told me it is supposed to be 230V here, but I measured the voltage for the incoming mains and reads 221V but that was with a digital meter though, I might check it with my AVO.

Nearly time to put it all together,

Will update as and when I get to that stage.

Best wishes

Ken
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Old 17th Nov 2016, 6:05 pm   #53
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Default Re: Ekco T344

Hi Stephen

Just checked the connections as per your advice and the set works ok, but there seems to be some confusion, on the ERT sheet it states for 230V G on 1, W on 3, R on 6, B on 7. Before I used your settings it was as per ERT sheet, and even then the EHT rectifier heat glows quite bright like it is with your settings, is this normal?

Ken
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Old 17th Nov 2016, 8:28 pm   #54
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Default Re: Ekco T344

OK, Ekco sheet for the mains dropper 230 volt
G on 1,
W on 3,
R on 6,
B on 7,

The previous advice in #51 is only in case the leads had been moved because of the width.
Go with the ones above and on the ERT sheet for standard settings.
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Old 17th Nov 2016, 9:27 pm   #55
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Default Re: Ekco T344

Hi Stephen

Thank you for that, I will re adjust as per your advice. Will update on this.

Best wishes

Ken
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Old 18th Nov 2016, 9:58 am   #56
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Default Re: Ekco T344

Hi Stephen,

Found a few more resistors that have gone high in their stated values so changing those as I find them. One other thing puzzles me is why the picture takes so long to be on the screen, after around five minutes or so the picture starts to appear faintly and as the set warms up the picture gradually becomes more visual and then settles to a decent picture, any thoughts on this would be helpful.

Ken
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Old 18th Nov 2016, 10:21 am   #57
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Default Re: Ekco T344

Measure the LT voltage on the heater of the CRT. See if it corresponds to the picture appearing at roughly the right voltage.
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Old 18th Nov 2016, 10:22 am   #58
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Default Re: Ekco T344

When the picture is faint is it about the correct size or much larger or smaller than normal.
Normal size would perhaps point to video chain upto including CRT, check voltages. Too large would suggest low EHT and narrow picture a line output fault.
Frank
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Old 18th Nov 2016, 11:27 am   #59
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Default Re: Ekco T344

The mains dropper colour/number codes are either printed/coded on a phenolic plate inside the 'set, ....or on (the rear of) the actual removable cardboard backing- i can't quite remember. Green and blue are annoyingly close in colour, probably due to age (mine, or the pigment)

Any stray solder will go back to at least the early seventies so at least you can be assured it is lead/tin!
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Old 18th Nov 2016, 5:16 pm   #60
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Default Re: Ekco T344

Hi Frank

The picture size is of normal size, I will check through the video chain to see if there is anything obvious voltage wise, and I will also check the heater volts on CRT, although the heater appears to be of normal brightness. Yes, the colour coding of the wiring is ok and the detail of tapings are on the card above the dropper which are the same as written on the ERT sheet.

More to follow

Ken
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