UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Specific Vintage Equipment > Vintage Television and Video

Notices

Vintage Television and Video Vintage television and video equipment, programmes, VCRs etc.

Closed Thread
 
Thread Tools
Old 17th Jul 2016, 11:35 am   #1
FERNSEH
Dekatron
 
FERNSEH's Avatar
 
Join Date: Mar 2005
Location: Gateshead, Tyne and Wear, UK.
Posts: 5,445
Default Ekco T221.

The attachment shows the appearance of the Ekco T221 which was brought to the shop yesterday for service by a forum member.
I have fond memories of this model as a similar set was bought by a relative who lived in St. Andrew's Road in Hove. The set was purchased in early 1955, I remember that the set was tuned to the temporary transmitter at Truleigh Hill. The channel number was B2.
The Ekco employs a 14" CRT, the Mazda CRM141 which has a round screen and unlike the Mullard 14" CRT which has a rectangular faceplate.

This early 13 channel receiver employs a split heater chain of 0.2 and 0.1 amps which merged into the 0.3amp heater chain for the tuner valves and the CRT.

DFWB.
Attached Thumbnails
Click image for larger version

Name:	Ekco T221.jpg
Views:	193
Size:	51.7 KB
ID:	127497  
FERNSEH is offline  
Old 17th Jul 2016, 12:03 pm   #2
Nuvistor
Dekatron
 
Nuvistor's Avatar
 
Join Date: Aug 2013
Location: Wigan, Greater Manchester, UK.
Posts: 6,683
Default Re: Ekco T221.

Cannot remember much about the set but the split heater chain I think was used in other Ekco models, I repaired Ekco sets with this type of chain, cannot which models though.

One I can remember was in a house owned by two sisters, the decor in the house was straight out of the 1920's, very clean but a 40 watt bulb with a green baize shade, always took an anglepoise lamp with me. Mind they very nice people .

Did the T221 use the type of LOPTX that disintegrated?

A frank
Nuvistor is offline  
Old 17th Jul 2016, 12:36 pm   #3
FERNSEH
Dekatron
 
FERNSEH's Avatar
 
Join Date: Mar 2005
Location: Gateshead, Tyne and Wear, UK.
Posts: 5,445
Default Re: Ekco T221.

Hi Frank,
The house I used to stay at where the Ekco was in service from 1955 to 1963 was exactly the same, just like the '20s in terms of décor. The ritual was at weekends the set was wheeled into the front room which was normally out of bounds during the week.
The T221 and the 17" version does use the moulded plastic line output transformer housing. We'll find out later today if it is serviceable.

DFWB.
FERNSEH is offline  
Old 17th Jul 2016, 7:41 pm   #4
Freya
Octode
 
Freya's Avatar
 
Join Date: Jan 2009
Location: Falmouth, Cornwall, UK.
Posts: 1,567
Default Re: Ekco T221.

My very first restoration was on the T221, it gives a striking picture and is a reliable favorite.
The only issue I had was diminishing EHT caused by the damp in the overwind, it needed to be connected to the dc power supply for 4-5 hours to drive out the moisture.
the knob legend rings are missing, still to be replaced sometime.
Attached Thumbnails
Click image for larger version

Name:	testcard.JPG
Views:	204
Size:	18.6 KB
ID:	127529  
__________________
Stephen
________________________

"It`s only an old telly"
Freya is offline  
Old 17th Jul 2016, 7:47 pm   #5
Heatercathodeshort
Dekatron
 
Heatercathodeshort's Avatar
 
Join Date: Jun 2005
Location: Warnham, West Sussex. 10 miles south of DORKING.
Posts: 6,604
Default Re: Ekco T221.

These are absolutely first class Ekco receivers from 1954, the first turret tuned Band 3 model from Ekco and probably the best of the early ITA receivers.
Very straightforward with no odd faults, an engineers delight.
Common faults as mentioned is the LOPT case [If disintegrating, easily fabricated from Paxolin]. It was the first model to employ the moulded case [ a bit like a railway bridge] unlike the earlier Ekco models that had the arched Perspex case. This early type never gave any problems.
It will be capacitors all the way. Decoupling, mains filter, boost, the ones that look like resistors, including the oil filled ones in the frame and the nasty Visconol if it has not been linked out already...
The tuner was used by Ekco with slight modifications from 1954 to 1965. One of the best multi channel tuners ever.
The Truleigh Hill relay at Brighton David was on channel 3. Rowridge was on the books and they didn't want the public to require another retune only 18 months later.
It was Folkstone that was channel 2. Very early translators commissioned in time for the Coronation.
[Oh by the way David, When I last visited the St Andrews Road area of PORTSLADE it was surrounded by the Sludge works on one side, the Council tip on the beach just about viewable from an upstairs bedroom if it were not for the huge fish guano works blocking the view at the bottom of the garden. Is it definitely Hove or the far more interesting industrial area of Portslade I have described?] Regards, John.
Heatercathodeshort is offline  
Old 18th Jul 2016, 1:47 pm   #6
FERNSEH
Dekatron
 
FERNSEH's Avatar
 
Join Date: Mar 2005
Location: Gateshead, Tyne and Wear, UK.
Posts: 5,445
Default Re: Ekco T221.

First observations confirm that the line output transformer housing is in good condition. The 20P4 is exhibiting a blue glow on certain parts of the glass bulb, it's the kind of glow that indicates a particularly good vacuum rather than a gassy valve.
No spark present at the anode of the U25. I'll unsolder this valve and see what happens.

A 1954 BBC report about the temporary transmitter at Truleigh Hill:

http://downloads.bbc.co.uk/rd/pubs/reports/1954-01.pdf

DFWB.
FERNSEH is offline  
Old 18th Jul 2016, 5:20 pm   #7
FERNSEH
Dekatron
 
FERNSEH's Avatar
 
Join Date: Mar 2005
Location: Gateshead, Tyne and Wear, UK.
Posts: 5,445
Default Re: Ekco T221.

As I expected there is no drive to the grid of the 20P4 line output valve.
The line multi-vibrator consists of one section of a 20L1 double triode and the screen grid of the 20P4, that forms the oscillator start up circuit. When fully functioning oscillator feedback takes the form of a 15pF pulse capacitor connected between the grid of the triode and a tapping on the line output transformer.

DFWB.
FERNSEH is offline  
Old 18th Jul 2016, 9:40 pm   #8
1100 man
Heptode
 
1100 man's Avatar
 
Join Date: Apr 2016
Location: Ventnor, Isle of Wight, & Great Dunmow, Essex, UK.
Posts: 986
Default Re: Ekco T221.

Hi all,
Many years ago, I bought a whole pile of tv's from Wooton Basset. Among them was an Ekco with a round tube. I never got round to doing anything with it and it has resided in my storage barn ever since being guarded by the woodworm and spiders. The picture at the start of the thread made me curious and I went to investigate my one. It is a T293 and peering through the back it also has a Mazda round tube. It also looked very unmolested and intact.
I assume this is a slightly later set than the T221. Does anyone know whether the chassis has much in common with the T221? Or indeed any other comments about the T293?
Cheers
Nick
1100 man is offline  
Old 18th Jul 2016, 10:06 pm   #9
Heatercathodeshort
Dekatron
 
Heatercathodeshort's Avatar
 
Join Date: Jun 2005
Location: Warnham, West Sussex. 10 miles south of DORKING.
Posts: 6,604
Default Re: Ekco T221.

Hello Nick,
The T293 is in fact a 17" model with a rectangular tube, either a CRM171 or CRM172. It also has provision for FM radio that performs surprisingly well.
It has very much in common with the T221 but uses the later .3amp Mazda range valves doing away with the three heater chains. It was a deluxe model at the time appealing to the traditional customer rather than the 'moderns.' Performance is outstanding as in common with all Ekco receivers.
It is very close to the T330/331 models released the following year. A search should bring up a couple I did some years back. Regards, John.
Heatercathodeshort is offline  
Old 18th Jul 2016, 10:07 pm   #10
FERNSEH
Dekatron
 
FERNSEH's Avatar
 
Join Date: Mar 2005
Location: Gateshead, Tyne and Wear, UK.
Posts: 5,445
Default Re: Ekco T221.

Hi Nick,
The Ekco models T283 and T284 were introduced in 1956, the T283 employs the round 14" CRT. The intro year for the T293 I'm not sure about as service information for it is in the 1957/57 R & T servicing book, but it might well be a 1956 model.
The principle difference is that these sets is that the Mazda 0.3 amp range of valves are employed. These valves are much easier to find compared with those 0.1 and 0.2 amp heater valves used in the T221.
Also the later sets have a simple and efficient line flywheel system.
As long as the line output transformer housing is OK all these Ekco sets are easy to get back to working order.

DFWB.
FERNSEH is offline  
Old 18th Jul 2016, 10:16 pm   #11
Heatercathodeshort
Dekatron
 
Heatercathodeshort's Avatar
 
Join Date: Jun 2005
Location: Warnham, West Sussex. 10 miles south of DORKING.
Posts: 6,604
Default Re: Ekco T221.

Quote:
Originally Posted by FERNSEH View Post
As I expected there is no drive to the grid of the 20P4 line output valve......DFWB.
Oh dear. I fear you are going to make a drama of this David.
Given a handful of bananas and the circuit diagram, my pet Orang A Tang, who is called 'Northern Angel' would have had a picture on that by sunset.. Regards, John.
Heatercathodeshort is offline  
Old 18th Jul 2016, 10:39 pm   #12
FERNSEH
Dekatron
 
FERNSEH's Avatar
 
Join Date: Mar 2005
Location: Gateshead, Tyne and Wear, UK.
Posts: 5,445
Default Re: Ekco T221.

Hello John,
Drama from me, surely not. OK then, News Flash! The failed line oscillator was caused by a faulty 20L1. I've replaced it and now there is drive to the grid of the 20P4. However, only a tiny spark is present at the U25 EHT rectifier. Remove the top cap from the U301 boost diode and the EHT comes up. it's gotta be a short circuit boost capacitor.
That's it for now, will return to the set tomorrow.

DFWB.
FERNSEH is offline  
Old 19th Jul 2016, 2:09 pm   #13
1100 man
Heptode
 
1100 man's Avatar
 
Join Date: Apr 2016
Location: Ventnor, Isle of Wight, & Great Dunmow, Essex, UK.
Posts: 986
Default Re: Ekco T221.

Hi John,
You are too good for me After you said that the T 293 had a rectangular tube, very faint bells started to ring! I vaguely recall that in the batch of Ekco tv's, one had a broken tube neck and was dismantled. The back was then used on the set I thought was a T293 just to confuse me.
Sure enough, I've just checked and the T293 back has a remote control socket!! I dug out the scrap chassis and lo and behold, it also has a remote socket. So that mystery is solved.
On removing the incorrect back and inspecting the set it has a round Mazda CRM 141 tube and the date on a capacitor is August 1955. It also has two aerial sockets mounted very close, side by side. I am guessing one for band 1 and one for band 3??
So there you go, is it another T221?
Cheers
Nick
1100 man is offline  
Old 19th Jul 2016, 3:54 pm   #14
FERNSEH
Dekatron
 
FERNSEH's Avatar
 
Join Date: Mar 2005
Location: Gateshead, Tyne and Wear, UK.
Posts: 5,445
Default Re: Ekco T221.

Normally these are the easiest sets to get going, however this one is proving to be the exception.
After replacing the boost capacitor other strange things started to happen.
The line oscillator would not start up unless it was shocked into doing so, like switching the set off and on a few times. This action would usually get the line oscillator started. Another problem is the line drive waveform was not continuous taking the form of bursts. Squegging in fact.
The EHT spark is also very weak. Well I've never replaced a line OP transformer in these sets but what about the scan coils? These have been disconnected and now there is a flame like spark present at the anode of the U25 EHT rectifier. Also the squegging has stopped and now there a continuous line drive waveform present at the grid of the 20P4.

DFWB.
FERNSEH is offline  
Old 19th Jul 2016, 7:34 pm   #15
Heatercathodeshort
Dekatron
 
Heatercathodeshort's Avatar
 
Join Date: Jun 2005
Location: Warnham, West Sussex. 10 miles south of DORKING.
Posts: 6,604
Default Re: Ekco T221.

Very early versions of the T221 did have a scan coil problem David. They are usually incredibly reliable and I find it odd that they should fail now. Has the chassis been played around with? If so you will have to start from scratch and check literally everything. You may have an incorrect connection somewhere or maybe someone has mixed up the scan coil connections but why they would do this with any Ekco is beyond me.
I have a T283 that uses the same scan coils. It's been hanging around for years with bits missing and you are more than welcome to the scan coils if yours are definitely faulty/shorting. John.
Heatercathodeshort is offline  
Old 19th Jul 2016, 8:41 pm   #16
FERNSEH
Dekatron
 
FERNSEH's Avatar
 
Join Date: Mar 2005
Location: Gateshead, Tyne and Wear, UK.
Posts: 5,445
Default Re: Ekco T221.

Hi John,
It's all very strange. Unplug the scan coils and the EHT goes up and the oscillator squegging stops.
Next, connect up the scan coils again and disconnect one of the wires to the scan coil socket, the fault returns even though the coils are in a sense fully disconnected.
In the T221 the two sections of the scan coils are series connected to the line transformer in the normal manner, one end to the boost rail and the other to a tapping on the line OP transformer. Where the set differs from others is that the width and linearity coils are connected between the two sections of the scan coils. This circuit arrangement was carried forward to the 1955/56 models including the T293.
From 1957 on the width control circuit was simplified consisting of a tapped resistor in the HT supply to the boost diode. Models T310 and T311.

DFWB.
FERNSEH is offline  
Old 19th Jul 2016, 8:54 pm   #17
TonyDuell
Dekatron
 
Join Date: Jun 2015
Location: Biggin Hill, London, UK.
Posts: 3,016
Default Re: Ekco T221.

Could it be :

A short between the 2 windings on the width control

A short between the line coils and the frame coils?
TonyDuell is online now  
Old 19th Jul 2016, 9:05 pm   #18
Heatercathodeshort
Dekatron
 
Heatercathodeshort's Avatar
 
Join Date: Jun 2005
Location: Warnham, West Sussex. 10 miles south of DORKING.
Posts: 6,604
Default Re: Ekco T221.

My thoughts exactly Tony. David, try disconnecting the frame coils completely and see if it makes any difference. I wish I could find the Ekco notes for 1954/5. I will have another look. J.
Heatercathodeshort is offline  
Old 19th Jul 2016, 9:18 pm   #19
Heatercathodeshort
Dekatron
 
Heatercathodeshort's Avatar
 
Join Date: Jun 2005
Location: Warnham, West Sussex. 10 miles south of DORKING.
Posts: 6,604
Default Re: Ekco T221.

Hello David,
I found these notes quicker than I had first thought. This is from 'James Huxleys' service dept. British Radio and Television. June 1956. J.
Attached Thumbnails
Click image for larger version

Name:	Ekco T221.jpg
Views:	116
Size:	128.9 KB
ID:	127622  
Heatercathodeshort is offline  
Old 19th Jul 2016, 9:31 pm   #20
FERNSEH
Dekatron
 
FERNSEH's Avatar
 
Join Date: Mar 2005
Location: Gateshead, Tyne and Wear, UK.
Posts: 5,445
Default Re: Ekco T221.

Hi John,
when I return to the workshop tomorrow I'll disconnect the frame coils, it's an easy task, just unsolder the wires to the scan coil socket.
I've found a scan coil assembly which was removed from a scrap TMB272, it's possible these will work in the T221. Circuits are very similar.

DFWB.
FERNSEH is offline  
Closed Thread

Thread Tools



All times are GMT +1. The time now is 5:49 am.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Copyright ©2002 - 2019, Paul Stenning.