PYE Chelsea CT200

[The teleman]

Hi guys , I'm at present trying to restore an 18 inch PYE Chelsea, this set is giving me a few head aches, after replacing the broken sliders and a few out of spec electrolytics powering up was short as the picture gradually got bigger as if it was ballooning so I powered off so not to cause any damage. I fear I may have been too late, the BU105 was s/c & the tuning capacitor 2.4n was leaky.

After replacement of the above the set now blows the HT fuse and R655 47ohm gets hot I have failed to find any s/c of any kind but I think this may be caused by failure of the LOPT.
Any suggestions would be appreciated

Chris

[thermionic]

It could be a faulty tripler loading the line stage..... as to other suggestions, maybe throw it in the bin!

Not a favourite set of mine. Never seemed to be able to produce a good picture , and ballooning was an original feature of these sets.

Good luck with it though, there can't be many of these left now.

Cheers. SimonT

[steve1010uk]

I would also suggest disconnecting the tripler,
also check the mica washer (if fitted i cannot remember) under the BU105
These were great looking sets and sold well on the reconditioned market but had absolutely lousy eht regulation.

Steve

[The teleman]

One of the first things I went for was the tripler , even with this disconnected the fault is still the same .
I must admit I haven't checked the mica washer this will be next on my list
Cheers
Chris

[MALC SCOTT]

Hi Chris, i should have a nos loptx for this chassis. I will have a look, Malc.

[neil29]

I've got the Philips version of this chassis. but i've yet to power it up so don't know what horrors await me .


Cheers
Neil.

[The teleman]

Originally Posted by MALC SCOTT

Hi Chris, i should have a nos loptx for this chassis. I will have a look.

Hi Malc, that would be great if you have, I feel sure it's the lopt that's at fault. Never had one go on this chassis before but after 40 plus years I suppose you can expect it.

Originally Posted by neil29

I've got the Philips version of this chassis. but i've yet to power it up so don't know what horrors await me

Hi Neil, don't be put off these sets aren't as bad as you think, as long as you have a good CRT & your set should be the later type with the higher focus voltage. The poor EHT regulation is the worst part about them.

Cheers
Chris

[Welsh Anorak]

Hi
That and the terrible IF unit! To repair you remove the IF sub-panel, then heat, lift slightly and resolder all the small capacitors inside - they were placed too close to the double-sided print. Don't expect too much from these sets, though they were greatly improved (not a difficult task) by the introduction of the CT200/1 with the HV focus CRT. The unipotential ones were very poor. Pye obviously thought that picture ballooning was a desirable feature at the time - witness the 697 chassis.
Always be careful when buying a 20" G8 560 that it isn't actually an 18" 570. You will be very disappointed (I speak from experience - the £30 still hurts!)
Am I imagining things or was there a Television article that experimented with feeding a unipotential tube with a 'proper' focus voltage?
Glyn

[Nuvistor]

Only remember the uni potential CRT, they were so poor compared to the similar size screens of Hitachi and Toshiba that the sets we ordered were sent back as unacceptable.

Frank

[Philips210]

Hi.

I'm trying to recall which sets employed these sub-standard unipotential focus CRTs. The only ones that I can think of were the Pye CT200/Philips 570 and the Thorn 8000. I'm sure there must have been others but I can't immediately think of any.

Regards
Symon.

EDIT: I always recall the terrible flaring on those tubes, usually the red gun was worst affected. If the contrast and brightness were kept reasonably low then a fair picture could be displayed. Those sets were only really viewable in a darkened room.

[Clydeuk]

I had a Ferguson fitted with the 8000 chassis in the late 80's. I'm sure it was 18 inch so probably used the unipotential CRT. The whole set looked very old fashioned with a mechanical tuner, but the picture was excellent. Did I get lucky?

[Philips210]

Hi.

From memory there was a 17" Thorn 8000 which had the unipotential focus CRT. There was a 8000A chassis with slight mods inc the mains dropper but I can't recall what CRT that set had. I think there was an 18" 8000 or 8000A but it's too far back in the distant past to be sure. I do know that the 19" 8500 had a normal HV focus CRT and that generally gave a very respectable picture.

Regards
Symon.

[Welsh Anorak]

Yes! I bought one in the late Seventies with pocket money I'd saved (£25) only to discover the CRT was beyond help. The Ferguson 3717 did look old-fashioned with a sort of American influence. The ones for rental were much more conventionally styled.
Many Japanese sets from the Seventies used low focus CRTs (e.g Hitachi CBP180) but despite looking a bit soft were nowhere near as bad as the Pye.
The Decca Bradford 18" used this CRT in the early version, later adopting a proper tube. The light cabinets were usually the early sets - all were denoted CS1830.
The Bush 18" used a high-focus PIL tube whose picture - if not its reliability - could at last give the Japanese sets a run for their money.
Glyn

[hans]

Who made these unipotential tubes? I have never seen a set with this kind of tube.

[Nuvistor]

The ones I saw came from Japan, but they had Mullard labels on them in the Pye sets.
The Hitachi sets had their name on them, I suppose Hitachi could have made there own but have no evidence either way.

The CT200 was an awful set, the Hitachi sets did have a softer picture than the high voltage focus type but very acceptable and extremely reliable.

Frank

[Welsh Anorak]

I had a feeling the 18" ones were supplied by Toshiba but I'm not sure. It seems they were a success in a well designed TV like the Hitachi.
And in the Pye? Hmmm.
Glyn

[hans]

What do you mean by "soft picture"? Lack of focus and/or contrast?

[Nuvistor]

That's the way I would describe it but not that bad as it spoiled the picture, in fact customers did not notice it on the Hitachi sets.
Frank

[The teleman]

Originally Posted by Philips210

I'm trying to recall which sets employed these sub-standard unipotential focus CRTs. The only ones that I can think of were the Pye CT200/Philips 570 and the Thorn 8000. I'm sure there must have been others but I can't immediately think of any.

The sets I remember having the unipotenial CRT was the Teleton with the metal case & the odd valves that no one else seemed to use at that time .

Chris