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Old 26th May 2017, 7:48 am   #21
Heatercathodeshort
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Default Re: EKCO 15" table model T164. 1952

Thanks Kevin, the 1939/46 15" console HMV 1803 still gives me a sly look every morning. I will get my own back..
Yes David it does work rather well. The harmonics of the spot wobble oscillator must be clear of the channel 1 frequencies. With the arrival of Band 3 it must have been more difficult to remove the patterns and by 1955/6 the spot wobble was gone.
Hello Lloyd, there are so many variations on these early triple link chassis. The symptoms indicate something amiss with the frame blanking or maybe the 1st anode supply decoupling. Should be an easy one . The low gain may well be the screen decouplers in the IF amplifier. They have a dramatic effect if O/C.John.
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Old 26th May 2017, 8:38 am   #22
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Default Re: EKCO 15" table model T164. 1952

Lovely job John as always, and yes the picture is bright!

Peter
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Old 27th May 2017, 6:22 am   #23
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Default Re: EKCO 15" table model T164. 1952

Another excellent job done john.
Bet you never thought all those years ago when the old lady gave you this set that it would be restored to perfect working order in 2017 ?
You were lucky those two dirty crm153 crt`s turned out to be good ones.
Could the other crm 153 be used in the HMV 1803 console if the emiscope crt is no good ?

Robin
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Old 27th May 2017, 8:10 am   #24
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Default Re: EKCO 15" table model T164. 1952

Thanks Robin. The pre war 15" EMI 3/6 in the 1803 is 100%. The EHT is mains derived of course and sits at just 4kv. What there is of a raster is very bright. It's just a major job that I will carry out this year. The receiver has an amazing history. Regards, John.
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Old 27th May 2017, 10:08 am   #25
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Default Re: EKCO 15" table model T164. 1952

Quote:
Originally Posted by Heatercathodeshort View Post
The spot wobble effect. Spot the difference. Regards, John.
That effect is very impressive and seems to greatly enhance the horizontal resolution. The first set I repaired as a teenager was a T231 and regardless of the frequency I always thought the spot wobble degraded the picture.

Peter
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Old 27th May 2017, 11:21 am   #26
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Default Re: EKCO 15" table model T164. 1952

Very nice restoration John.

Peter, the horizontal resolution stays about the same from what I see...
(The photos are not taken at the same height.)
Interesting effect, the spot wobble. I hadn't seen it illustrated so clearly. Thanks for these photos John.

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Old 27th May 2017, 12:22 pm   #27
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Default Re: EKCO 15" table model T164. 1952

The spot wobble oscillator frequency should in the order of 15Mhz with a some adjustment to remove any patterning. Didn't telecine CRTs use spot wobble to remove the line structure? Ekco was the only manufacturer to employ this method of line structure removal over a wide range of models. Other models that come to mind are the mighty HMV 1820 of 1952, the first 21" CRT TV to be marketed in the UK and the equally huge Murphy V290, another 21" model.

DFWB.

Last edited by FERNSEH; 27th May 2017 at 12:32 pm.
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Old 27th May 2017, 12:32 pm   #28
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Default Re: EKCO 15" table model T164. 1952

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Peter, the horizontal resolution stays about the same from what I see...
(The photos are not taken at the same height.)
Jac
Score zero for observation!

Doh!

Peter
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Old 27th May 2017, 1:18 pm   #29
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Default Re: EKCO 15" table model T164. 1952

Peter, I was first surprised of the resolution as well, but I couldn't quite believe it and started counting the bars...

David, it is interesting to know the spot-wobble frequency. Thank you. I was just wondering how high it had to be.

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Old 27th May 2017, 4:17 pm   #30
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Default Re: EKCO 15" table model T164. 1952

Hello Jac,
At 15Mhz there is absolutely no possibility of any degradation of horizontal resolution, also at such a high frequency it wouldn't matter if it was a an exact multiple of the line repetition rate or not.
KB employed another type line eliminator in the 1962/63 VV series dual standard receivers. The focus electrode was supplied with an adjustable negative going voltage. It was said that this introduced a degree of astigmatism in the vertical direction, thus filling the gaps between the lines.
OK for 405 lines but there was no facility to switch off the line eliminator on 625 lines.

DFWB.
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Old 27th May 2017, 9:13 pm   #31
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Default Re: EKCO 15" table model T164. 1952

Catching up with a few posts brought me to this thread. Once again John, an excellent read and a nice result too
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Old 28th May 2017, 7:39 am   #32
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Default Re: EKCO 15" table model T164. 1952

Hi John,

What an excellent set and what luck to have been given those two CRM153's all those years ago and better still they are good examples.

I enjoyed following the success of the CRT replacement and modifications to implement it, I also followed your explanations and descriptions of the various parts of the circuit alongside trader sheet 1087 which really helped paint the picture.
The way the spot wobble works is most interesting and I never knew that it operated on such a high frequency but then thinking about it, I guess it has to so as not to degrade the picture definition.

The only part where I found myself cowering behind my sofa was when I came across the image of that huge bulb face down on your work bench! YIKES!! You have to be brave to deal with a fearsome bulb like that! (waiting to be called a Wendywoo any minute now!)

An excellent job and write up done John, thanks for sharing it here

Cheers
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Old 28th May 2017, 8:36 am   #33
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Default Re: EKCO 15" table model T164. 1952

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Wendywoo
Ha! ha! Lee and thanks for your comments. That is a word, once heard and never forgotten! Regards, John.
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