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Forum 141

Ekco TC435

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PYE625
(@pye625)
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Hi all,

After the delivery of this and a Pye TV14 all the way down from Crusty Towers, (Grateful Thanks to Valvebloke and Cathovisor),
I couldn't wait to have a peek inside the Ekco. (The Pye looks good too, but one at a time :aao )

After a re-form of the multi-section electrolytic via a 15w lamp-limiter and removal of the first valve in the heater chain to allow HT to rise, things looked promising.

Anyway, I applied limited power with all valves fitted and was greeted by noise from the speaker and line whistle.
After a few moments of carefully watching for any signs of distress, a raster appeared but with frame collapse.
I switched off to avoid any further stress as there are a large number of rather sick looking sticky waxies to be changed.
So it looks like good news as far as the Lopt and tube are concerned.
I will start the restoration process shortly !! :qq1

To understand the black art of electronics is to understand witchcraft. Andrew.

 
Posted : 13/04/2015 10:34 pm
Cathovisor
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Started already?! That's enthusiasm for you :qq1

 
Posted : 13/04/2015 10:51 pm
neil1974
(@neil1974)
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I recognise that set :aaj .

Cheers
Neil.

 
Posted : 13/04/2015 11:03 pm
PYE625
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I recognise that set :aaj .

Cheers
Neil.

He he, I thought you might....it's a well travelled set :qq1

Just ordered some 0.1uf 1kv caps....what a time to find I ain't got none :bbd

To understand the black art of electronics is to understand witchcraft. Andrew.

 
Posted : 13/04/2015 11:13 pm
sideband
(@sideband)
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Ahh! The excellent Pye 11U chassis!

I've just been watching a vintage film on mine. I shall be following this thread with interest. :thumb

 
Posted : 13/04/2015 11:30 pm
Marc
 Marc
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Hi Andrew,

Well done on bagging the Ecko, :aad
I always fancied it myself but I couldn't exactly sneak it out of Crusty's tucked under my jumper could I ! :bba

Looking forward to seeing it up and running

Marc.

Marc
BVWS member
RSGB call sign 2E0VTN

 
Posted : 14/04/2015 12:14 am
freya
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Hi Andrew,

I think I have the genuine Ekco sheets for this one, not that you are likely to need them.

 
Posted : 14/04/2015 9:11 am
crustytv
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I can trump you :qq1 I have the entire service manual. In fact in addition to many of the sheets mentioned, I have a few of these type of manuals for Ferranti and EKCO.

Anyway, if required it can be scanned but in essence its an 11U which is more than adequately covered in the library already.

Great start Andrew and I'm sure we will see a Test card very soon.

CrustyTV Television Shop: Take a virtual tour
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Posted : 14/04/2015 9:26 am
Nuvistor
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I had forgotten how many wax capacitors were in the chassis. The 19 inch version T433 was my main TV running 625 only from 1970 to about 76. After refurbishing it was a very reliable TV and gave very little trouble capable of a cracking picture.
Frank

Frank

 
Posted : 14/04/2015 9:32 am
The_Teleman
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I remember seeing this set at Chris's . I notice the set has a Mazda gold star crt .
I have the 19 inch T433 they are nice sets .
Chris

 
Posted : 14/04/2015 7:56 pm
PYE625
(@pye625)
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Ello all,

Well, she is all but running now after a re-cap, just awaiting some 1kv 0.1uf (used a couple of 47n 1kv temporary).
I'm plagued by a strange frame fault though.
There seems to be plenty of gain as far as height is concerned, but the bottom half of the picture is folded over and squashed towards the middle.
Linearity is awful, very stretched at top but can be adjusted down, however this causes the bottom to reduce too.
I've got the service manual so will probe around properly later, already had to replace a selenium rectifier in the frame stage this was completely open circuit. I used a 1n4148, not entirely sure this is suitable :aaq

I will post some pictures tonight so is more clear to see. :qq1

To understand the black art of electronics is to understand witchcraft. Andrew.

 
Posted : 15/04/2015 9:59 am
Tazman1966
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Have you checked the cathode electrolytic and associated bias resistor. That could cause symptoms such as this.

My Uncle had one of these sets back in the 70s. He bought it second hand and it was great on 405 but rubbish on 625!

Tas

 
Posted : 15/04/2015 10:41 am
Refugee
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Are you sure the 1N4148 has a high enough voltage rating for a valve output stage?
It could be working like a zena diode if it is not up to the job.

 
Posted : 15/04/2015 10:49 am
Cathovisor
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Hi Andrew,

As has already been said, check the cathode bias resistor and the associated decoupling electrolytic for the frame output valve - this is a classic fault.

The 1N4148 should be fine if it's doing what I think it is.

Edit: it appears on the 67 chassis as an "Interlace filter" in the grid circuit so if it's doing the same thing here, it should be fine.

 
Posted : 15/04/2015 10:52 am
Nuvistor
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Hi Taz,
The valve UHF tuners used in these sets were very deaf, I was lucky, Winter Hill is line of site about 8 miles away and with an MBM46 in the attic (still there and working on Freeview) I had no problems. It was used only on 625 with a really good picture.
I am not sure why these tuners were so poor, they used the same valves as Philips tuners which were much more sensitive. The Ekco had the enough IF gain after they replaced the last IF with a EF184, I think is was, frame grid anyway. I think it was just a poor UHF tuner design.
Frank

Frank

 
Posted : 15/04/2015 12:33 pm
PYE625
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An update....
I checked all of the suggestions and found the items in question all to be ok, except the cathode resistor was slightly high at 410 ohms so replaced it with a wire wound 390 ohm. Made no difference, as expected.
Now, I more or less ruled everything around the PCL85 out because waveforms all look exactly as in the manual.
My only suspicion now was the frame output tx and scan coils.... :ccf

But wait !!.....whats this? a thermistor type VA1054 on the scan coils that reads an unstable 50 ohms and drops only 3-7 ohms when heated.
So, I short it out and gain a perfect raster.
Anyone know the spec. of a VA1054?? :bba

First pic is with height and linearity controls set for the maximum I could get.
Second is with sensible adjustments and height pot in a midway position.

Set is on 625 lines and the UHF tuner seems pretty sensitive, surprisingly.

To understand the black art of electronics is to understand witchcraft. Andrew.

 
Posted : 15/04/2015 7:49 pm
Nuvistor
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I have looked on line and cannot find VA1054, lots of thermistors but not that one. The thermistor is there to combat the rise in the scan coil resistance from cold to normal working temp. Suggestion is to measure the difference in the scan coils and try to match a thermistor for that range with perhaps a shunt resistor across the thermistor to get a better match.
I had to smile, while searching for the VA1054 I can across A Practical TV from 1965 with an article by L. Lawry-Johns on servicing the earlier chassis Ekco T418 and he mentions the thermistor for causing frame collapse.
http://americanradiohistory.com/Archive ... 965-09.pdf

Looks a good bright picture on the set.

Frank

Frank

 
Posted : 15/04/2015 9:54 pm
PYE625
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Hi Frank,
Thanks for the input....I will have a play with some thermistors :qq1
Here is a pic with it working on 405....I can't believe how bright and sharp the tube is, the pic don't really do it justice :)

To understand the black art of electronics is to understand witchcraft. Andrew.

 
Posted : 15/04/2015 10:35 pm
neil1974
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That's a very good picture you have there :aad . and i'll be coming round to collect the set now it's working :aaj :aak .

Cheers
Neil.

 
Posted : 15/04/2015 10:41 pm
PYE625
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Thanks Neil.. :bba
What amazed me is not only did it work perfect on 625, sound too, but the definition on 405 is fantastic.
I was pulling my hair out a bit with the frame fault, but got it sorted after a fashion...just gotta select a suitable thermistor and job done.
No fiddly alignment needed either :aad
I changed all the wax candles and there were one or two resistors notably R119 270k which was in a yellow sleeve coming from the Lopt that had gone high. Its in series with C94, a 12pf high voltage cap. I think it must be some sort of feedback network.
Anyway, a bit of tidying up and I'll post some more pics later in the week. :qq1

To understand the black art of electronics is to understand witchcraft. Andrew.

 
Posted : 15/04/2015 11:24 pm
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