EKCO TMB272. Questions.

[Geoff 555]

Hello all, I could do with some help please.A short intro. to the set. Thanks to HCS (John.) and his invaluable help it was sorted bit of a job because it had been got at with wiring missing etc. The LOPX was a queer one as well ***.
At some time in the past it had had a bad clout in the rear corner on the aerial socket side.Right hand side looking from the front.The aerial plug could not be put into the socket because the chassis was bent out of shape. Dropped on that corner I should think.A lump hammer and block of wood came into use.
Now down to the problem, the picture is tapered It is not the mask out of shape which is what I first thought, using a test card the left side vertical line is 5 3/4" tall, the right hand side is 5 1/2" tall. I know it is only small but it is really noticeable. Height apart from the taper, width,focus etc. is good.
If I was really picky then the rectangle with lines on the bottom right corner of
the test card is about 10% smaller. The scan coils and focus magnets are square on the tube and the neck is central in the mounting bracket. I cant seem to alter the shape.

*** LOPTX while discussing the problems of no EHT with John it transpired that the replacement transformer that had been fitted had actually been made by him. Hows that for a coincidence.
No offence was intended by calling it queer I was having a leg pull.

Something happened yesterday when I turned it on and this is not a leg pull but the raster had moved a good 3/8" to the right and when I removed the cover off the set I was staggered to see that the raster had moved back.
I havnt put it back as I was waiting for suggestions.
Puzzled.
Cheers.
Geoff.

I have just had a thought, I had to remove the tube to straighten and sort various things out I did take pictures and made notes but as it was obvious that it had been taken apart before is it possible that the scan coils were put on 180 degrees out, it is possible.

[high_vacuum_house]

Good evening,
Could it be (and I dont want to appear gloomy ) that if the telly has been dropped in the past that the electron gun in the CRT has had its alignment between electrodes disturbed ?

If so then moving the scan coils and focus coils slightly out of alignment to the chassis then the scan errors could be minimised or eliminated.

Christopher Capener

p.s Is the ion trap magnet in the right place ?

[Geoff 555]

Hello Christopher it's good to hear from you, I did wonder but I actually tried another tube and there was no difference. I guess I should have mentioned that. Thank you for the suggestion. The ion trap is in the correct position as far as I know. It alters the brightness and shifts the picture but doesn't seem to make an awful amount of difference to the geometry but I will bare it in mind.
Cheers.
Geoff.

[Geoff 555]

Hi just to clear up one thing the scan coils are the right way round IE: not back to front but it does look as if there may be something missing, according to the layout in the service info. going from the front of the tube neck backwards the order of bits should be a large washer then a distance piece of some sort then the scan coils and possibly the same kind of thing again, it's a line drawing in plan view and the rear of the coils are hidden by a bracket.There is no washer and no distance piece the coils being pushed up firmly to the bulb and on the rear of the coils are two thick felt washers. Could anybody kindly through some light on this as to what is correct please.
Ta.
Cheers.
Geoff.

[Lloyd 1985]

Hi,
I don't know if this will help, but I've dug out a couple of old photo's of when I took mine to bits to clean it a few years back! I don't think it had been got at untill I got hold of it, so should be correct (unless you count the mouse damage!!). I really must get round to doing something with it

Regards,
Lloyd.

[Heatercathodeshort]

Hello Geoff,
Now this is a very strange one. I have never seen this fault on any Ekco receiver and certainly not on the little TMB272. A raster that is not square, tapered in any way is usually due to faulty deflection coils. Various faults with the coils can cause this such as mechanical alignment of the saddle windings, distortion to one winding or possibly a shorted turn, the later being unknown with Ekco coils. The construction of Ekco components is of high quality and I feel that the impact damage might have done something odd. When aligned correctly, i.e. parallel top and bottom, the coils will appear to be biased to the right. This is quite normal and is due to the twisting action of the beam, an effect I have only seen with Ekco receivers but very noticabale with the 200 and 300 series receivers. A stinker can be when a bar magnet has fallen from a linearity or width adjuster and stuck itself near to the CRT..I'll say no more. Check it is in place on the width inductor. I'm pretty sure the TMB272 uses one.
If that LOPT case is constructed from PAXOLIN with the top dipped in pitch I did indeed build the complete item including the windings. I was 13/14 at the time, working for D&B Television at South Wimbledon working after school and Saturdays. I made hundreds of them together with the complete Ekco range. I used to cut the Paxolin sides and top out of large sheets using a band saw that was horrendous. It used to send its blade flying out when it broke. It was in a damp basement with no electrical earth so used to get shocks from the metal work on damp days. Sounds like something out of a Christmas Carol. I have attached the notes I made all those years ago. They still make sense! Regards, John.

[IJK2008]

Hi Geoff

I've sent you a PM about your set.

Ian

[Geoff 555]

Hello thank you to all, yes it is one of yours John. Now the picture of Lloyds 1985's set has raised a question which may be the answer. My set is dated 1956 so I dont know if there were any mods to later ones. The bracket that the focus magnets are mounted on ( which in turn mounts on a cross bracket with 2 brass cheese headed screws.) is completely different. It still has the shift plate but 4 extra slots and screws so that the focus magnets can be shifted so they are non parallel with the tube neck. 2 screws can not be reached with out taking the magnet assembly off. I havnt touched these as the magnets are square with the tube neck. If all else fails I will mark where they are and have a play.
I thought it was a unusual one , never seen anything like it.
The large washer and spacer ( rubber "O" ring ??) that appears to be on the EKCO service sheet seems to be missing both on mine and also on Lloyds.
Thanks for your help and thoughts.
Cheers.
Geoff.

[Geoff 555]

Hello just a quick line to clear up a couple of things, the picture shifting when / after removing the covers was not me being mad but a real silly, the focus control pokes out of a hole in the back and the focus magnet slides are sloppy, which I am going to cure as it seems to be a problem, moved the control sideways when removing the cover and ------- picture moves.
Spent nearly 2 hours moving every adjustment in small amounts and it makes not the slightest difference.
A few more things to try yet, will keep you up to date.
Cheers.
Geoff.

[murphyv310]

Hi.
One other possibility is that the metal framework has become magnetised. Is it possible the set has been kept near a strong magnet or has a speaker been sat on the set or very close by?
It also my be possible if the above is wrong to introduce some small disc magnets around the windings of the scan coils to straighten up the picture.
I also would be inclined to try a second set of scan coils.

[Heatercathodeshort]

I had thought of that one Trevor. That gave me the idea with the missing bar magnet scenario that I once encountered with a receiver years ago. I found it stuck to the tube bowl clamp! The metal work of the TMB272 is mostly Aluminium. I think it is quite possible that this slight fault may have been present from new and never complained about. The deflection coils may be out of tolerance with possibly the saddle windings being very slightly out of line. They are very solidly constructed and I would imagine difficult to take apart and that would create a can of worms you don't need. I would guess that any coils from the 70 degree 200/300 series would be suitable but the possible disturbace/breakdown caused by fitting replacements is probably not worth the risk. Regards, John.

[Boom]

Hi Geoff. If the large washer is the one that I think it is then its purpose is to stop the scan coils rubbing against the aquadag and shorting.

You also say the picture changed when you took the back off. Did you turn the set around to do this? If so it could be localised magnetisation.

[Geoff 555]

Hello , scan coils set me thinking ,if I slacken off the bracket (that goes across the chassis) that holds the focus magnets and puts pressure onto the rear of the scan coils pushing them up the tube neck, the coils are very sloppy on the tube neck and can alter the picture a lot.
On the EKCO service card, as I have mentioned before, the large washer and what I assume is a large"O" ring is missing. These would move the coils back a bit and also locate them positively ??
The card should be below. What do you think, should they be there or not? I have some 1 and 2 mm. polycarbonate sheet so I can make a washer and probably 'fake' an "O" ring, but really need to know if they should be fitted before opening up another can of worms by diving down to many side routes if you see what I mean.

Thank you.
Geoff.

[Alistair D]

What about cutting up some erasers to make wedges instead of the O ring?

Al

[Geoff 555]

Hello just an update for you. A very generous forum member provided a set of scan coils and fibre washers etc. and that has cured the problem, comparing the coils then I could find no difference, apart from on the original ones there was a white powdery deposit over the area in contact with the plastic transparent sleeve on the neck of the tube. I tried various things and the only thing that did anything was WD 40. I dont know if a plastifier ( not sure if that is the right word.) had migrated out of the plastic into the coils and effected the insulation, may be?
Thank you.
Cheers.
Geoff.

[IJK2008]

Hello Geoff

Glad they helped.

Ian