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PYE CT 72

 
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Re: PYE CT 72

Post by nuvistor » Mon Jul 13, 2015 1:54 pm

Thanks for the info Andrew, I just don't remember.

Is there a circuit easily accessable?

 
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Re: PYE CT 72

Post by crustytv » Mon Jul 13, 2015 2:36 pm

.
691.jpg
691 S/S Line Oscillator and output stages

 
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Re: PYE CT 72

Post by nuvistor » Mon Jul 13, 2015 4:26 pm

Thanks for posting the circuit, I had the AVO ( I think that was the make) multiplier to go with the AVO 8 meter for checking EHT in the sets. I had forgotten how nice a simple the Pye Line stage was.

Frank

 
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Re: PYE CT 72

Post by PYE625 » Mon Jul 13, 2015 5:37 pm

While I'm waiting for the caps to arrive for the line stage, I thought it would be good to examine the state of some electrolytics dotted about the place.
Not a pretty sight, and although working, I think I will replace them as most are leaking or have decayed.
See last pic below as a typical example.

Here is the "thingy" board what does the colour and the glass delay line with the cover removed....
Attachments
rsz_img_1918.jpg
rsz_img_1917.jpg
rsz_img_1921.jpg

 
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Re: PYE CT 72

Post by Refugee » Mon Jul 13, 2015 6:15 pm

It is unusual for those blue electrolytic capacitors to fail. You will not need to change many.

 
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Re: PYE CT 72

Post by PYE625 » Mon Jul 13, 2015 6:27 pm

It seems that the physically small ones are the worst, and most have the rubber ends all decayed and split open.
Electrically, they generally seem ok, although some have more than doubled in value.

On the CDA board, there are some 4uf 350v black callins type and in use, one of them got quite warm pretty quickly, so I best replace them too.

 
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Re: PYE CT 72

Post by PYE625 » Mon Jul 13, 2015 6:46 pm

That makes sense Jeffrey, I applied the rated voltage to one, the current started to rise and the case became warm. (A 25uf 25v type.)

I wonder when the set was made, 1969 or 1970?
Many date codes on the components are all 69, but of course the set could have been made the next year.

 
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Re: PYE CT 72

Post by nuvistor » Mon Jul 13, 2015 7:52 pm

Is there a country of origin on the delay line, just noticed the month, OKT, German, Dutch?

Frank

 
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Re: PYE CT 72

Post by jjl » Mon Jul 13, 2015 9:00 pm

The 4 largish can electrolytics in yellow jackets are marked Callins. I don't think I've ever seen a Callins can electrolytic before. I've seen plenty of the black plastic variety though.
Was there a connection between Callins and Daly? They both seemed to appear and disappear at around the same time i.e. first seen (by me) in equipment from the mid '60s, gone by the mid '70s. I seem to recall one or the other of them being an Irish company.

John

 
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Re: PYE CT 72

Post by malcscott » Tue Jul 14, 2015 12:10 am

Any Callins caps must be replaced! Malc.

 
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Re: PYE CT 72

Post by PYE625 » Tue Jul 14, 2015 9:46 am

malcscott wrote:Any Callins caps must be replaced! Malc.


Perhaps the black plastic ones yes, but the larger metal canned ones seem to be perfect.
I have carefully replaced all of the smaller black Callins type and have not found any of them to be electrically useable.

Upon measurement, their values are way high and it has been mentioned that this is due to excessive leakage.
When using a bench PSU to apply some volts, just below the rated value on the cap, I found that most of them draw current of say a mA or so and in some cases, it started to rise. The same can be said for some of the smaller blue caps that I have replaced too.

The danger is of course that they will explode with some force as the electrolyte heats up :aac
I don't want that happening in this set !
So, in this case, prevention is better than cure.

 
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Re: PYE CT 72

Post by malcscott » Tue Jul 14, 2015 10:20 am

As this set is 45+ years old i would imagine that most of the caps will be past their best. Also best to replace all three 12k wire wound resistors on the cda board with stand off types, Malc.

 
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Re: PYE CT 72

Post by ekcopyephilips » Wed Jul 15, 2015 8:46 am

That set looks amazing.

Is it a 691 chassis? Looks more 693 to me. The 691 had a very tall EHT stack, yours hasn't got that. Do the date codes on your components vary hugely? I have an Ekco badged 697 chassis and dates on capacitors range from 1972-74. So mine must have been one of the last made. Also indicates that Pye must have had huge stocks of components to be using 2 year old parts during manufacture. But then it was the 70's and 'just in time' manufacturing methods were not used back then - at least not by British manufacturers anyway.

 
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Re: PYE CT 72

Post by PYE625 » Wed Jul 15, 2015 9:02 am

ekcopyephilips wrote:That set looks amazing.

Is it a 691 chassis? Looks more 693 to me. The 691 had a very tall EHT stack, yours hasn't got that. Do the date codes on your components vary hugely? I have an Ekco badged 697 chassis and dates on capacitors range from 1972-74. So mine must have been one of the last made. Also indicates that Pye must have had huge stocks of components to be using 2 year old parts during manufacture. But then it was the 70's and 'just in time' manufacturing methods were not used back then - at least not by British manufacturers anyway.


Thanks...I am assuming it is a 691, but the first was a dual-standard chassis with GY501/PD500 in the EHT, this one is single standard and has a tripler.
It looks to be a single standard version 691 chassis. 693 used a varicap tuner, this one is mechanical.
All date codes range from Feb 69 to Aug 69, so your guess is as good as mine. :bba
It could have been made late 1969 or into 1970 is my guess. :aaq

 
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Re: PYE CT 72

Post by sideband » Wed Jul 15, 2015 10:52 am

PYE625 wrote:All date codes range from Feb 69 to Aug 69, so your guess is as good as mine. :bba
It could have been made late 1969 or into 1970 is my guess. :aaq


Is there a serial number intact? I might be able to decipher the year code from that.

 
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Re: PYE CT 72

Post by PYE625 » Wed Jul 15, 2015 11:03 am

Hi, well it looks to be 810080.
That is printed beneath the model number on the crt shield, on the card back it only has the model number.

Cheers,
Andrew

 
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Re: PYE CT 72

Post by PYE625 » Wed Jul 15, 2015 1:01 pm

Sad or what !!

I checked out the Mullard factory and date codes on the PL509/PY500 and they check out to be Philips Heerlen Holland, April and May 1968.
The three PCL84 check out to be Mullard Blackburn June 1969.

Of course this bears no relation to the date of set manufacture, but was fun to do lol. :aal

 
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Re: PYE CT 72

Post by sideband » Wed Jul 15, 2015 1:26 pm

PYE625 wrote:Hi, well it looks to be 810080.
That is printed beneath the model number on the crt shield, on the card back it only has the model number.

Cheers,
Andrew


Hmmmm! I don't think that's the serial number....at least not the whole of it, not enough numbers. 810 could be 10th week of 1968 but I think that is too early seeing as you have date codes of 1969. Typical Pye Sn would be xx01 910 123456 where (in this case) xx are two letters indicating factory of manufacture, 01 would be first production change (so could be 02, 03 etc) 910 would indicate 10th week of 1969 followed by the actual serial number. When the next decade was reached an extra digit was added to the first three so 7910 would indicate 10th week of 79 and that carried on as far as I know. Of course Philips used the same coding.

 
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Re: PYE CT 72

Post by PYE625 » Wed Jul 15, 2015 1:42 pm

Perhaps the true serial number will forever be a mystery as on the card back, there is an area that looks to have had a sticker on it but has fallen or peeled off. :ccb

 
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Re: PYE CT 72

Post by malcscott » Wed Jul 15, 2015 2:01 pm

The s/n for my Ekco CT107 is on a label on the degausing shield, Malc.

 
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Re: PYE CT 72

Post by PYE625 » Wed Jul 15, 2015 3:09 pm

Right !
Got the little devils before they get me.....
Attachments
rsz_img_1937.jpg
rsz_img_1934.jpg

 
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Re: PYE CT 72

Post by Katie Bush » Wed Jul 15, 2015 9:37 pm

Was that the big brute, next to the blue/white (blue/yellow) Dubilier under TB/power chassis?

 
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Re: PYE CT 72

Post by PYE625 » Wed Jul 15, 2015 10:07 pm

Katie Bush wrote:Was that the big brute, next to the blue/white (blue/yellow) Dubilier under TB/power chassis?


Hi, this one was from the frame board, but there was another in the line stage too.
I'm still waiting for the 0.47uf 1000v to arrive, the last one to be fitted and then it should be all systems go!

Like the electrolytics, the Dubilier types were generally measuring much higher on a capacitance meter than their rated value .
I found all but one was in fact slightly leaky when tested at 500vdc (half their rated voltage).
I have been fitting LCR types as replacements and naturally, these have no leakage whatsoever.

Granted, the Dubilier plastic types are not as leaky as old wax capacitors, but in high voltage stages they are not trustworthy.

 
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Re: PYE CT 72

Post by PYE625 » Thu Jul 16, 2015 6:15 pm

Hi,
Now up and safely running again after the cap change.

Checking EHT level.
I made up a string of 10x 33meg hv 1watt resistors in series and inserted them in PVC tubing.
I started with the set switched off of course and a careful routing of the resistor network from the anode cap of the tube.
I used an AVO 8 to measure the current at the earthy end of the string to ground.
I set the EHT preset to minimum and slowly increased it until I had a reading of 76 micro-amps on the AVO.
This should correspond to approximately the correct voltage of 25kv EHT.
It couldn't have been too far out as the position of the preset was pretty much as it was before.

Last pic is of the resistor string.
Attachments
rsz_img_1945.jpg
rsz_img_1947.jpg
rsz_img_1951.jpg
Last edited by PYE625 on Thu Jul 16, 2015 6:48 pm, edited 1 time in total.

 
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Re: PYE CT 72

Post by malcscott » Thu Jul 16, 2015 6:25 pm

Nice work !

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