Pye Chelsea TV Help Required please

[Beamcurrent 62]

Hello I'm a new member and this is my first post I am after some advice please. I have a Pye Chelsea 18" colour television that is in showroom condition but is dead. I have checked everything that I can think off and have come to the unfortunate conclusion that the line output transformer has failed. Is this common on this particular chassis? I'm not over familiar with these sets but would like to restore it as it belonged to a very dear friend of mine so any help would be greatly appreciated thank you.

[Sideband]

It's 40 years since I repaired one of these. I never remember replacing a line output transformer.....lots of triplers but never LOPT's. Most common fault (apart from the tripler failing) was the power supply (thyristor...and I think there was an official mod for this using a BT121).

EHT regulation on these was dire since they were a 'bare-bones' TV to bring a low-cost non-portable colour TV to the market but they gave reasonable pictures. Pye CT200 chassis first on the market in 1974. The Philips equivalent was the G18C570.

What checks have you done to arrive at a LOPT fault? Mind you, after 50 years ANYTHING is possible!

[slidertogrid]

Sideband is correct the transformers rarely failed when the sets were in service but unfortunately after all these years they do fail.
I had a set with a duff LOPT some time ago. More recently my mate had a set which had been stored for years, he had it working for a while before the LOPT failed. He so far has been unable to find a replacement in fact I think he may have disposed of the set.

There were two versions of the CT200 early ones had a 'low focus' tube, later ones were conventional with a different CRT and base. I think the LOPT would be the same but not the tripler. Yours is the later version.

Unfortunately if you find a second hand LOPT you may find it won't last long.

[Philips210]

The original version with the low focus tube used the 713 chassis. Later high voltage focus tube 18" sets used the 715 and 717 chassis. As Beamcurrent 62's set has slider controls on the front it has the 717 chassis. A good servicing article on these chassis can be found in TELEVISION magazine, November 1979 issue by forum member Mike Phelan. This is part 3 of a series on the Pye solid state sets. Parts 1 and 2 cover the large screen sets 725 (90 degree) and 731 etc (110 degree).

There was also a footnote to the series on the 713/715/717 by Harold Peters in the December issue.
Hope that helps.

All of these magazines can be downloaded from World Radio History website https://www.worldradiohistory.com/Practical_Television_Magazine.htm

Regards,
Symon

[Welsh Anorak]

You're lucky in that this has the later tube which performed better than the original low voltage focus types.

Are you sure it's the LOPT? Like everyone above I've had my moments with these, but never a faulty LOPT. I assume the PSU is working when unloaded and the line oscillator is doing its job? Not wishing to doubt your diagnostic abillties, but it would be nice if it was something easier to obtain!

If the LOPT has failed then do check for one of those nasty unreliable dull green tuning capacitors across the BU205.
If you need a manual I probably have an original you're welcome to.

[its ur aerial]

Every days a school day ! I didn't realise there were two versions of this set, so I assume the later model did not suffer with the infamous poor EHT regulation ?
I can only recall servicing the version with poor focusing and EHT issues.
Like others have mentioned, all the ones I recall fixing, suffered defective triplers, a BU205 or two and those green caps mentioned by Glyn ring a bell
By disconnecting the LOPT and the Line O/P stage can you get the power supply to run and produce some HT ?
Ken G6HZG.

[toshiba tony]

I'm retired now but I'm sure both sets were atrocious at regulation. They ballooned like mad if the contrast or brightness was turned up. I wasn't too keen on the unipotential tubes but the later ones were marginally better

[Welsh Anorak]

I'm afraid I agree. Most manufacturers would perhaps have added some regulation, but customers didn't seem to notice. Looked nicer than the Thorn 8000, and much cheaper than the Sony so they sold well.

Very careful setting up will help with the poor picture and ballooning, and you'll doubtless need to lift and resolder the ceramic capacitors in the IF stage.

But first let's see about the suspect LOPT.

[Beamcurrent 62]

Hello to all and thank you for all your help and advice regarding the Pye Chelsea TV all advice is greatly appreciated. I am working somewhat blind as I do not have a circuit diagram for this chassis but I have this morning carried out some further tests. The power supply is running but it is being dragged down causing F691 - the 500ma fuse - to fail. This appears to be the rail that feeds the line output stage. On replacing the fuse I have slowly run the set up via my variac and, with the tripler disconnected, I have noted that the line output transformer "overwind section" gets excessively hot and there is a strong acrid smell. I have checked all capacitors, diodes and other components around the line output section and have replaced the green line tuning capacitor as a matter of precaution. I have also checked the mica washer between the BU205 and chassis as I have read that these are prone to failure. On removal of the line output transformer the HT is no longer being dragged down so I am of the opinion that a replacement transformer is required. I will now go transformer hunting and will report back soon! Regards, Ian - Beamcurrent 62

[Philips210]

Hello Ian.

It does indeed look like there's a problem with the LOPT. The EHT tray in these sets is a doubler. If you download the Nov 1979 issue of Television magazine from World Radio History you'll find most of the circuit diagram in the article I mentioned above. It shows the 715 and 717 versions. While you have the LOPT out. If it's easy to dismantle it then maybe remove the overwinding, reassemble and refit the LOPT to see if the line output stage will run.

Regards,
Symon

[Welsh Anorak]

As Ken says, every day's a school day!

Could you post a picture of the LOPT? I have a couple of orphan LOPTs knocking around - I have no idea which TVs they're for!

My manual has gone AWOL - in fact I'm sure I passed it on to a forum member, though I thought I had a spare.

[G6ONEDave]

I have the Pye 713 service manual with the 715/717 addendum that I could scan if it's of any help. It should be near enough for you. Please PM me if interested, it will be a download from a link as it's going to be too large to email.

Dave

[dazzlevision]

Here are a few close-up photos of the LOPT, tripler and line flyback tuning capacitor on a Pye CT200/1 that I used to have. They may help ID a suitable LOPT.

This set had a slider type (high voltage) focus control on the CRT base PCB - just like the later Philips G8 chassis sets (550 series).

[Beamcurrent 62]

Originally Posted by G6ONEDave

I have the Pye 713 service manual with the 715/717 addendum that I could scan if it's of any help. It should be near enough for you. Please PM me if interested, it will be a download from a link as it's going to be too large to email.

Dave

Hello Dave thank you for your kind offer I have managed to get hold of a manual but thank you anyway. I'm sorry for my late reply I have been away for a while and so not had access to my PC.

Kind regards, Ian.