It is currently Sun Dec 17, 2017 2:40 pm

PYE CT 72

 
Posts: 290
Joined: Fri Jul 29, 2011 8:42 pm
Location: St Albans

Re: PYE CT 72

Post by Tazman1966 » Tue Jul 21, 2015 5:24 pm

The set EHT control alters the boost volts hence the increase in width with EHT.

Tas

 
Posts: 715
Joined: Tue Jan 27, 2015 2:02 pm
Location: Chatteris, Cambs

Re: PYE CT 72

Post by PYE625 » Tue Jul 21, 2015 9:59 pm

PYE625 wrote:Now, there is another inductor, L39 I think, that has a core that is fixed. If I insert a small screw driver into the coil, the inductance of course alters slightly and the width will increase. I am not sure of the purpose of this coil, but it goes from the wiper of the line shift control to the scan coils plus convergence circuitry. (L40 the width control is on the other side of the scan coils).
:aaq


I had a closer look at this coil and the "apparent" fixed slug. The slug is a small smooth ferrite rod about an inch and a half long. The inside of the former is smooth too, without the usual thread.
It is not fixed, but was pushed or had moved all the way in as it was loose. ( I was pushing it, but it was at an end stop, so that's why I thought it was fixed.)
I temporarily removed the coil and ferrite slug. I put a small piece of rubber sleeve in the coil former and gently re-fitted the slug, but leaving enough sticking out so I could adjust it.
Then I re-fitted the coil and switched on.
I adjusted the slug for maximum width which is now more sensible.

Furthermore, the maximum width corresponds with a minimum AC voltage across both R229 and R230 to ground, which had previously overheated and I had to replace them both. They now run much cooler along with the line shift control which is mounted on the chassis and I had been surprised how hot this had been previously.
So, I think that the core of L39 was mal-adjusted and was causing the lack of width.
The proper width control can now be reduced to a more normal setting. :) :)

 
Posts: 290
Joined: Fri Jul 29, 2011 8:42 pm
Location: St Albans

Re: PYE CT 72

Post by Tazman1966 » Wed Jul 22, 2015 8:02 pm

That's excellent news :) I've not heard of it before.

 
Posts: 715
Joined: Tue Jan 27, 2015 2:02 pm
Location: Chatteris, Cambs

Re: PYE CT 72

Post by PYE625 » Wed Jul 22, 2015 8:48 pm

Cheers Tas,

It could be my imagination, but I am certain that the convergence panel is running cooler too.
All the pots are mounted on a metal frame and before the adjustment of the coil L39, it was pretty hot.
Now, it is just warm.
Same goes for the area where the line shift pot is mounted and R229/30 as I said above.

The convergence needed slight adjustment upon the alteration of L39 and the line linearity too, but I have found that there is plenty of range in the controls (especially width), and they just "feel" right without being at or near their limits.

I am sure that L39 must be a factory set-up adjustment and is probably to compensate for the line scan coils in some way.

Thanks for all the input, it has been much appreciated.

 
Posts: 1141
Joined: Mon Jul 25, 2011 11:37 am
Location: Willington, Co Durham.

Re: PYE CT 72

Post by malcscott » Thu Jul 23, 2015 12:22 am

There are a couple of electrolytics on the convergence panel which may need to be replaced, Malc.

 
Posts: 489
Joined: Tue Mar 24, 2015 12:01 am
Location: Wigan

Re: PYE CT 72

Post by nuvistor » Thu Jul 23, 2015 1:38 pm

You are getting it nicely sorted out, I have forgotten so much about these sets and to think they were my everyday bread and butter repairs 40 years ago.

Frank

 
Posts: 715
Joined: Tue Jan 27, 2015 2:02 pm
Location: Chatteris, Cambs

Re: PYE CT 72

Post by PYE625 » Tue Jul 28, 2015 9:00 am

It's proving to be a reliable set so far, been using it for a couple of hours or so most days.
Time to assemble the legs and install it in a proper domestic setting....I NEED MORE ROOMS !! lol :bbd

 
Posts: 134
Joined: Sat Aug 09, 2014 6:53 pm

Re: PYE CT 72

Post by The_Teleman » Sat Sep 26, 2015 12:19 am

What a fantastic set , I love these PYE sets in fact most of my collection has been reduced to collecting this make of set .
I have yet to start collection colour sets but it looks like you have given me the drive to look for some sets like yours .
Chris .

 
Posts: 715
Joined: Tue Jan 27, 2015 2:02 pm
Location: Chatteris, Cambs

Re: PYE CT 72

Post by PYE625 » Sat Sep 26, 2015 3:16 pm

The_Teleman wrote:What a fantastic set , I love these PYE sets in fact most of my collection has been reduced to collecting this make of set .
I have yet to start collection colour sets but it looks like you have given me the drive to look for some sets like yours .
Chris .


It is a nice set and easy to work on...I'm very pleased it has give you encouragement Chris. :aad

 
Posts: 715
Joined: Tue Jan 27, 2015 2:02 pm
Location: Chatteris, Cambs

Re: PYE CT 72

Post by PYE625 » Mon Mar 28, 2016 4:30 pm

As it has been a bank holiday, I thought I'd give her an airing.....
Attachments
rsz_002.jpg
rsz_1003.jpg
rsz_004.jpg

 
Posts: 134
Joined: Sat Aug 09, 2014 6:53 pm

Re: PYE CT 72

Post by The_Teleman » Mon Mar 28, 2016 4:52 pm

Brilliant !

Chris

 
Posts: 1450
Joined: Wed Jul 27, 2011 10:14 am
Location: gloucestershire

Re: PYE CT 72

Post by rob t » Mon Mar 28, 2016 5:45 pm

If i remember correctly the line linearity damping resistor is 1.5 k
may be my mind is playing tricks but the srictions were on the right looking from the front ?
Rob T

 
Posts: 489
Joined: Tue Mar 24, 2015 12:01 am
Location: Wigan

Re: PYE CT 72

Post by nuvistor » Mon Mar 28, 2016 7:14 pm

Ah well, looking from the front I thought those striations from that faulty damping resistor were on the left, one of us is going to be correct Rob.

Frank

 
Posts: 1450
Joined: Wed Jul 27, 2011 10:14 am
Location: gloucestershire

Re: PYE CT 72

Post by rob t » Mon Mar 28, 2016 7:37 pm

I expect its me frank .
i have had to start writing things down now so they sink in.
Rob T

 
Posts: 437
Joined: Fri Aug 26, 2011 10:45 am
Location: Gateshead

Re: PYE CT 72

Post by Focus 2 » Tue Mar 29, 2016 6:12 am

Fantastic! Don't know how I missed this thread. I estimate the date of manufacture will be 1969 or 1970.
Interesting to see this when the earlier dual standard version is being discussed.
Brian

 
Posts: 715
Joined: Tue Jan 27, 2015 2:02 pm
Location: Chatteris, Cambs

Re: PYE CT 72

Post by PYE625 » Tue Mar 29, 2016 8:20 pm

A further minor thing, I have always been concerned about how hot the frame output transistors got.
After a while, you could barely touch the heatsink.

I had tried a couple of stick-on heatsinks, but decided to pull them off and spray paint the original heatsink a matt black,
as on other chassis of this type I have seen in pictures.

After this, I read the service manual properly re the frame stage and actually took the time to set it up PROPERLY :ccb
VR24 was not set correctly.... the manual states that if the rail to rail voltage is 40vdc, then you adjust VR24 for 22vdc between PL10D and C.
After this was corrected, the output transistors are just warm to the touch.
Attachments
rsz_001.jpg
rsz_004.jpg

 
Posts: 489
Joined: Tue Mar 24, 2015 12:01 am
Location: Wigan

Re: PYE CT 72

Post by nuvistor » Tue Mar 29, 2016 8:43 pm

The frame output stage was always near the margins on its output. Properly setup it did the job but there were often cases were this was just enough. After saying this the circuit gave me little trouble.

Frank

 
Posts: 2986
Joined: Thu Jun 28, 2012 12:20 pm
Location: The Vale Of York

Re: PYE CT 72

Post by Katie Bush » Tue Mar 29, 2016 8:58 pm

I remember once watching my granddad lick his finger and brush it against those output transistors - I also remember the gentle "SHSSTTT" as the wetness sizzled away!

Some seemed to run hotter than others.

Marion

 
Posts: 715
Joined: Tue Jan 27, 2015 2:02 pm
Location: Chatteris, Cambs

Re: PYE CT 72

Post by PYE625 » Fri Apr 01, 2016 10:37 pm

Just a couple more pics to squeeze in...
Attachments
rsz_1005.jpg
rsz_11006.jpg

 
Posts: 489
Joined: Tue Mar 24, 2015 12:01 am
Location: Wigan

Re: PYE CT 72

Post by nuvistor » Sat Apr 02, 2016 12:58 am

Great picture.

 
Posts: 437
Joined: Fri Aug 26, 2011 10:45 am
Location: Gateshead

Re: PYE CT 72

Post by Focus 2 » Sat Apr 02, 2016 8:56 am

Excellent picture and convergence.
Cheers
Brian

 
Posts: 715
Joined: Tue Jan 27, 2015 2:02 pm
Location: Chatteris, Cambs

Re: PYE CT 72

Post by PYE625 » Sat Apr 02, 2016 9:24 am

It barely needed much adjustment in the convergence department from day one really, and I still get that tingle of pleasure each time I switch her on and see such an amazing quality of picture.
A real gem of a set that is a treasure I will look after whilst I'm her custodian.

 
Posts: 290
Joined: Fri Jul 29, 2011 8:42 pm
Location: St Albans

Re: PYE CT 72

Post by Tazman1966 » Mon Apr 04, 2016 2:31 pm

Superb!

Previous

Return to Colour Television



Who is online

Users browsing this forum: No registered users and 2 guests