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PYE 741

Pre War 240/405, Post War 405 Line, B&W Dual Standard, Colour Dual Standard, B&W S/S 625, Colour S/S 625 line, Hybrids. Standards converters & modulators, video recorders.
 
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PYE 741

Post by The_Teleman » Sun Jul 24, 2016 3:58 pm

Hi guys , this is my latest addition to my collection of PYE sets ,
It's a PYE CT260 ,741 chassis this is the 26 inch 110 degree quick warm up CRT version of the CT222 , this set has a date stamp of 23 Dec 1976. I believe these sets had the nickname of Lego sets due to the ease of panel swapping
This set while not the best condition outside the inside is quite clean
The CRT tested good on my tester with good balance of all three guns .
Before powering up I checked a few of the notorious items , ie the mains filter capacitor
dry joints .
These sets as with many of the thyristor power supply types don't like variacs , so full mains was applied
The sound came on but no raster CRT heaters glowing nicely ,focus voltage & a1 voltage
present but no final anode volts
A replacement EHT tripler cured the no final anode volts
The picture at this point was awful , convergence errors , frame fold over ,short width & no colour
So I decided to tackle the frame & width fault first . On checking the HT volts it seemed a bit low at 125 volts , without making any adjustment I checked a couple of small electrolytic caps in the power supply ( lower right side )by replacement & this bought up the voltage to 145 volts , not having a manual at this stage most of the setting up was pure guesswork & a vague memory of one of these sets years ago .
The next stage to get attention was the frame panel ( upper right) checking the electrolytics revealed most had suffered with the passing of time so these where replaced with new ones
The set now looked a lot better with good frame Lin & full width , the convergence errors looked better too
I noticed someone in the past had soldered three resistors on the print side of the timebase panel (centre left) I must admit this sort of thing is a pet hate of mine but they had to stay for now
The colour was still missing & the grey scale was poor , replacing three 39 k resistors around the thick film unit on the decoder panel(upper left) restored a decent grey scale & cleaning of presets again on the decoder restored the colour
The picture now looked good but a little grainy, replacing the tuner ELC1043/06 cured the grainy fault
This is the first attempt at a colour set restoration for many years
my next set might be my CT205 when I've sorted the cabinet of this one .
The set needs setting up just waiting on a copy of the manual to get it set up correctly .
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Re: PYE 741

Post by malcscott » Sun Jul 24, 2016 4:23 pm

I have nos i/f gain modules for this chassis. The later Ledco type with the sawf fitted. The original ones were very unreliable due to dry joints etc. Check the 3 x 470k resistors which feed the A1 pots and the two resistors which supply the A1 from the tripler. There is a removable solder pad on the pcb which brings one or both resistors into cct, Malc.

 
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Re: PYE 741

Post by jayceebee » Sun Jul 24, 2016 4:37 pm

That looks F.A.B. Chris :thumb

A rare 110 degree delta crt set saved, the Mullard ELC1043/06 did seem to fail differently to the more common /05 version.

I live in hope that a Thorn 4000 or a Rank Z719 will turn up one day.

John.

 
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Re: PYE 741

Post by nuvistor » Sun Jul 24, 2016 4:38 pm

Surprisingly I don't remember too much about the 741 chassis except it was not that reliable. They were capable of a good picture though. I cannot remember if the 90deg chassis came out before or after the 110 deg but the 90 deg I found a much more reliable chassis. I don't recall the Lego name but I never had panels to swap.
Anyway you have one and made it work again, excellent work.

Frank

 
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Re: PYE 741

Post by The_Teleman » Sun Jul 24, 2016 4:40 pm

Hi Malc ,

This set has had the I/f unit replaced with the new type & the 470k resistors
Are on order , these are the ones someone put on the solder side of the pcb
But they are old carbon type

Cheers

Chris

 
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Re: PYE 741

Post by Tazman1966 » Mon Jul 25, 2016 8:59 am

Nice to see one of these into preservation. Oddly, it seems that far more of the Pye Hybrids have survived...

Tas

 
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Re: PYE 741

Post by nuvistor » Mon Jul 25, 2016 9:34 am

Tazman1966 wrote:Nice to see one of these into preservation. Oddly, it seems that far more of the Pye Hybrids have survived...

Tas

There were probably more hybrids made if you count the 691, 3, 7 series. These 110deg sets were soon replaced on the production line with the 20AX and 30AX CRT's. Plus has mentioned, I found them quite unreliable compared to other sets, perhaps others had better results with them though.
They were also more expensive than the 90deg sets, so perhaps less were made due to less demand.

It's good this one has been saved, they are part of the development history of CTV.

Frank

 
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Re: PYE 741

Post by slidertogrid » Wed Jul 27, 2016 11:04 am

I found the 110 degree sets to be fairly troublesome in fact I stripped a Dynatron set out and fitted a new G11 inside the cabinet as the owner was fed up with the original chassis going wrong. I think the G11 faired a bit better as it was a later model which were much better than the first generation sets.
The 725 90 degree sets were much better, they were made as a budget set It was an interim replacement for the CT205 until the G11 was ready the 90 degree delta tubes were coming to the end, 20AX was on the horizon.
I don't know if they were better because they had an easier time driving a 90 degree tube or if lessons had been learned on the older chassis.
The 110 degree sets suffered from one particularly nasty fault, the A1 capacitor would go short take out the tripler, lopt, line output transistor and blow the HT fuse. apart from the struggle to get the line output transistor out which was soldered firmly to its fixings without cracking the panel thr Ht fuse being open left the smoothers fully charged to catch out the unwary..
The same circuit was used in the later sets but I never had one fail, maybe the capacitor was changed to a different type?
Ex rental sets often bristled with parts on the back of the line panel the original part was often still in place often just snipped or prized out of the panel one end.
Field Engineers must have felt the set would be more reliable with parts mounted on the cooler side of the panel...
:cch
Rich.

 
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Re: PYE 741

Post by The_Teleman » Wed Jul 27, 2016 11:40 am

Hi , I serviced lots of these sets back in the day & never found them to be any less reliable than the 90 degree version
I did find that poor repairs by engineers not familiar with these sets made them unreliable
But if you done a good repair & set them up correctly they never became a problem
Mostly the sets I found using this chassis was the Ekco version with the black front
I don't know if these where early models but the did seem to suffer with heat problem
Most of the panels I came across were discoloured & in some cases looked burned
Most of the faults did occur in the line section but if you used the correct components & not try to fit resistors of higher wattage to try & stop them going as often the sets lasted quite well

This particular set is a prime example most components are as original all the safety resistors have been replaced with the correct type where they had been upgraded & fitted back in the original position
I would of preferred the 22 inch 90 degree set as I don't like lugging around these heavy lumps but this was a nice example & im a sucker for anything with the PYE logo

Thanks for all your comments

Chris

 
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Re: PYE 741

Post by malcscott » Wed Jul 27, 2016 11:53 am

Hi, i serviced hundreds of these and the 90 deg models. When Rediffusion took over Tates TV shops the w/shop flooded with them, never seen so many bodged up repairs! The 90 deg set gave good results and i can,t recall ever replacing a CRT in them. The 110 deg, that is another story. The line output panel had far too much work to do, too much heat generated. If the e/w cct had been fitted to a seperate pcb to disperse the heat, things could have been much better, Malc.

 
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Re: PYE 741

Post by nuvistor » Wed Jul 27, 2016 5:56 pm

The_Teleman wrote:Hi , I serviced lots of these sets back in the day & never found them to be any less reliable than the 90 degree version
Chris

I suppose it's all relative, we were selling Hitachi and Toshiba sets in the middle 70's when the 741 was introduced. We just put those out and very rarley had to repair them. The 725 chassis for me did give less trouble than the 741 but we probably all had different experiences whatever model it was. I do think that the 90deg circuits were not as stressed as the 110deg sets and that was part the problem.

The later Hitachi and Toshiba sets seemed to give as many problems as other UK sets.

Frank

 
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Re: PYE 741

Post by 405 fan » Wed Jul 27, 2016 7:03 pm

Hi
I have a CT222 and it's been very reliable. My aunt & uncle bought a ct222 new in 1975 and it ran faultlessly until 1983 when the A1 cap blew .
Regards.
Gary.

 
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Re: PYE 741

Post by slidertogrid » Thu Jul 28, 2016 10:25 pm

That's the model with the tuning drawer, the later sets were Ct227 they had an all wood effect cabinet with a more conventional push button unit. They looked a bit like the early PYE G11 from the front.
I liked them, they were no trouble compared to the earlier 110 degree sets.
The earlier Ekco 110 degree with the black front had different coloured bulbs that lit up when the channel was selected. I always thought that looked a bit cheap. most of the 110 degree sets were well cooked and sometimes horribly bodged by the time the rental boys flogged them off. I can see the pile of dross now, Panels all unplugged, sliders all broken. piled high at Carters in Ilkeston!
:bba
Rich.

 
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Re: PYE 741

Post by Doz » Thu Jul 28, 2016 10:44 pm

My first colour TV!

Brings back fond memories.


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