Pye T25Y New Zealand B&W Hybrid TV Set - UK Vintage Radio Repair and Restoration Discussion Forum

GLENZ32 · 9th Apr 2019, 1:51 am

Hi everyone, its been a rather long hiatus since I have posted or done anything with my old TV sets. The last time I posted on here was back in 2014.

This was due to everything being put into storage in 2015 (due to major life changes) and have in the past 6 to 8 months relocated brought a house which has garage/s (so the lockup was cleaned out - what 'fun' that was) and a room off the side of one of the garages which I've turned into a workshop so projects and tinkering can take place again.

So this Pye 19 inch set featured here is a hybrid model made here in New Zealand dating from 1969. Am uncertain if this is based on a British or Australian chassis/layout, someone here may recognize this as something familiar or a clone of a native model.

These were a very common and came in a range of CRT sizes from 12 inch up to 26 inch. The chassis also went through some various changes over the years, the earlier versions were all valve, where as the later chassis like this one here had transistors scattered around the video drive & amplifier section and vision and sound IF stages and sync separator stages. The smaller sets also used a compactron in the fly back section, a 38HE7 which was the line output pentode & boost diode in one bottle.

I acquired this TV which was back in the late 1990's. Back in 2003/2004 I made a half hearted attempt to get it working, found there were major issues with the vertical/horizontal so decided it was too hard at the time so put the thing back together and shelved it.

15 years on and I decided that for my first project in the new workshop was to resume repairing this and to get it working properly this time around.

Upon applying some mains after its long slumber the set came to life displaying a crappy raster crackling audio and some arcing noise accompanied by hissing EHT which turned out to be the lead from the line output transformer to the top cap of the DY87 was about to fall apart. Once that was repaired and sorted I moved on to looking into the vertical to see what was up there.

Discovered pretty quickly with the aid of the circuit that some idiot (not me

) had in the past attempted to repair it by putting wrong value components in place not to mention a cap tacked across pins on ECL85 on the print side to try and compensate for whacked out frame operation which wasn't even meant to be there! So the putting the correct parts back in place and removing the bodged capacitor, all voltages around the valve measured right and the vertical was starting to look more normal again and height/linearity controls now worked properly!

Moving onto the horizontal oscillator, the sync was poor and lock was very touchy and it didn't take long to discover that the phantom bodger had been there as well changing component values and linking things out again around the ECF802. I wonder what the logic behind doing this and obviously there was some fault that kept this person experimenting around with the circuit and the reasons why - who knows? Putting the right value components back in this area made things a bit happier and more stable and correct volatges were resumed and I could now obtain good horizontal sync and lock.

With these two areas sorted I then focused on the resistors that were used in this model and several others. These mustard bodied types are notorious for going high ie 47k reading 70k, 100k reading 180K etc so I make a point of checking all of them and replacing and this was no exception as I ended up changing nearly all of them, I probably didn't have to due to tolerances within the circuit but as I have a 'ton' of NOS resistors and paranoid about old crappy resistors!

Its more a piece of mind thing knowing that they've been done. I did leave one or two in there that weren't in any crucial positions and did notice slight improvement as I methodically put new ones in and tested the set in between.

Once I'd done the resistor-rectomy, then removed the leaky/aged old can multi section filter capacitor and fitted replacements using three separate ones. Went through and replaced other old capacitors that looked a bit tired or were not reading right on the cap tester.

Things were now starting to look quite good by this stage so I set about cleaning the case and the front panel/glass etc when the picture vanished...Hmm ok what did I do?? A bit of probing and it returned. Swing the chassis up - no picture, swing it down - picture! Turned out to be a poor solder joint on tag strip in the fly back area probably done by me as I did work on that bit in the past. Then the picture began to fade away at will now - what the heck! Glancing at the filament on the CRT it was dimming up and down. This was an intermittent break in one of the filament wires so fixed that and then the other filament pin terminal decided to break off on tube neck socket!

This thing was starting to have a go at me.

A few other things went wrong as they do put a wrong value resistor in and was greeted with magic smoke from it the moment I applied power, slipped with the meter probe and blew up the 2nd vision IF Bf137 transistor, burnt the side of my hand a little on the baking 38HE7 during a moment of being careless- man those things get super toasty hot! But not too many hiccups really.

Once I had the set running stable, went to set the picture up using the test pattern and got it reasonably well adjusted there's a slight geometry error horizontally but not going worry about that after all its a 50 year old TV. The yoke correction rings have been adjusted to best as possible.

So after all that and taking 15 years to finally fix this thing,we now have working usable TV! The photos don't do the image justice its bright, sharp with good contrast so the CRT is showing no signs of age at this stage.

I'll run it over the next weeks to see if any further teething issues crop if but overall am happy with the outcome and feel a sense of achievement on this since it was probably one of the very first valve sets I decided to restore.

I'm wondering about my next project for the bench...Hmm..it could be another Pye, I have a few of them!

Thanks for reading my ramblings if you got this far. Enjoy the photos!

Cheers

Glen.

linescan87 · 9th Apr 2019, 8:16 am

Hi Glen,

That's a cute tv and a nice little write up. Those resistors can be way out alright. Cracking crt.

John Joe.

dazzlevision · 9th Apr 2019, 8:49 am

Welcome back Glen.

The cabinet style is very reminiscent of early 1960s Pye UK sets in moulded cabinets with cream coloured fronts, the VHF turret tuner and two rotary controls, such as the VHF/495 only 17” V220. See here: https://www.vintage-radio.net/forum/....php?p=1043708

There’s also the dual standard TV2: https://www.radios-tv.co.uk/communit...-sets-aquired/

However, the chassis bears no resemblance to Pye group UK mono chassis of the late 1960s.

Hybrid tellies · 9th Apr 2019, 9:25 am

What a nice looking set and its looking good. Very interesting write up especially seeing that it uses the E range of valves instead of the normal P range of valves. That combined line output/boost diode is also strange sight to our eyes, its quite amazing that the valve holder can deal with the high voltages present that we normally see on the top caps of the line output and boost diode valves.
Many of us forget that in Australia and New Zealand they did not like using AC/DC techniques and most sets of this vintage used an isolating mains transformer.

Synchrodyne · 9th Apr 2019, 9:53 am

Very true. Thus in this part of the world, E-series valves were normal (Everyday, if you like) whilst P-series valves were abnormal (Peculiar).

Cheers,

G6Tanuki · 9th Apr 2019, 11:56 am

Fascinating to see a Compactron in use. I don't think any UK-made TVs ever used them, they were almost exclusively a US thing.

usradcoll1 · 9th Apr 2019, 5:07 pm

Quote:

Originally Posted by Synchrodyne

Very true. Thus in this part of the world, E-series valves were normal (Everyday, if you like) whilst P-series valves were abnormal (Peculiar).

Cheers,

In the early 60's, Motorola started using P-series valves in some of their models in two separate series chains, connected series-parallel at the start to accommodate the 600ma CRT. Most of the valves were sourced by Philips, from Holland. The PL500 drove a 23" CRT with ease with only a 140v HT source.
I have a 11" Panasonic hybrid color set that uses all P series valves in the circuits that use valves.
Dave.

mark pirate · 9th Apr 2019, 7:55 pm

Good to see you back again Glen, I also have not tackled a restoration for a while now, but hope to get back to the mountain of sets later this year.

I agree that the front does look very similar to early 60's UK Pye sets, I have a 17" model in an all plastic case in the pile.

The chassis has an american look to it, especially fitted with that Compactron, not sure it was a good idea to combine the line output with the boost diode though

Mark

FERNSEH · 9th Apr 2019, 10:48 pm

Information for the Compactron sweep tubes types 38HE7, 38HG7 and 37HK7.
Line output pentode and damper diode in the same glass envelope.
From Wikipedia, more information about the Compactron tubes:
https://en.wikipedia.org/wiki/Compactron

DFWB.

GLENZ32 · 10th Apr 2019, 1:32 am

Thanks John and yes those resistors are used in a lot of our sets made here

The CRT has held up well considering its probably seen a fair bit of use in its life.

Quote:

Originally Posted by linescan87

Hi Glen,

That's a cute tv and a nice little write up. Those resistors can be way out alright. Cracking crt.

John Joe.

GLENZ32 · 10th Apr 2019, 1:34 am

Never heard this quote before regarding the E and P series valves!

And very true

Quote:

Originally Posted by Synchrodyne

Very true. Thus in this part of the world, E-series valves were normal (Everyday, if you like) whilst P-series valves were abnormal (Peculiar).

Cheers,

GLENZ32 · 10th Apr 2019, 1:39 am

Hi Mark, thanks and its good to be back and being active with my old TV projects again.

Yes that compactron does run rather hot and the socket is quite discoloured but isn't falling to bits 'yet'

It would be nice to find out where the chassis design was based on. But cosmetically it does resemble a UK based Pye look.

Hopefully you'll get back into the swing of things and tackle a set or two later on

Quote:

Originally Posted by mark pirate

Good to see you back again Glen, I also have not tackled a restoration for a while now, but hope to get back to the mountain of sets later this year.

I agree that the front does look very similar to early 60's UK Pye sets, I have a 17" model in an all plastic case in the pile.

The chassis has an american look to it, especially fitted with that Compactron, not sure it was a good idea to combine the line output with the boost diode though

GLENZ32 · 10th Apr 2019, 1:42 am

Thank you

Looking at those pictures the set is very much a copy of the UK style of cabinet. I'd like to know what the chassis was based on. I'm guessing either Australia or the USA, but then again it could be a NZ only design.

Quote:

Originally Posted by dazzlevision

Welcome back Glen.

The cabinet style is very reminiscent of early 1960s Pye UK sets in moulded cabinets with cream coloured fronts, the VHF turret tuner and two rotary controls, such as the VHF/495 only 17” V220. See here: https://www.vintage-radio.net/forum/....php?p=1043708

There’s also the dual standard TV2: https://www.radios-tv.co.uk/communit...-sets-aquired/

However, the chassis bears no resemblance to Pye group UK mono chassis of the late 1960s.

GLENZ32 · 10th Apr 2019, 1:54 am

Thanks Simon, it was only the Pye sets that used the compactrons. All of out other brands used converntial line output and boost diode as seperate PL/EL36 or EL/PL500/04 and EY/PY88/800 etc. The NZ made Philips were all series strung using P series valves. But we did have some Philips kitset models which were isolated mains only.

Quote:

Originally Posted by Hybrid tellies

What a nice looking set and its looking good. Very interesting write up especially seeing that it uses the E range of valves instead of the normal P range of valves. That combined line output/boost diode is also strange sight to our eyes, its quite amazing that the valve holder can deal with the high voltages present that we normally see on the top caps of the line output and boost diode valves.
Many of us forget that in Australia and New Zealand they did not like using AC/DC techniques and most sets of this vintage used an isolating mains transformer.

1100 man · 10th Apr 2019, 10:24 am

Hi Glen,
It's always fascinating to see TV's produced in other parts of the world- good write up too!

First thing I spotted was the mains transformer which would be a very unusual thing to find in UK set. Series heaters, 'P' series valves and mains droppers were more the norm for us.

The Compactron is something I've never seen before. I suppose on the face of it, it makes some sense to combine the LOP valve & efficiency diode, but it must get incredibly hot!

Obviously on separate valves, top cap connections are used for the high pulse voltage connections. Having these on the valve base, I would have thought tracking on the valve base would have been a common problem.

For sets using a mains dropper for the heaters, two separate valves require less power to be got rid of via the dropper, so the Compactron would not be attractive for UK manufacturers.

I'm off to have a look at your website!

All the best
Nick

GLENZ32 · 11th Apr 2019, 1:36 am

Hi Nick, as I mentioned the majority of our sets were mains isolated, Philips being the only sets that weren't. The compactrons do get 'very' hot pays to keep fingers and other things well away when servicing these!! Amazingly the back cover isn't melted in where the compactron sits pretty much at the top of the chassis and a fair bit of heat radiates up.

You'll enjoy my website, unfortunately I can't update it anymore won't let me login or change anything and I don't know why.

Cheers
Glen

Synchrodyne · 11th Apr 2019, 3:18 am

Notwithstanding its monochrome receiver history, Philips NZ adopted isolated power supplies for its colour TV receivers, the first of which was the K9. Presumably the chassis was modified from the European original, which I think had a non-isolated supply. As far as I known the Australian version of the K9 also had an isolated power supply, as well as differing in having a rotary tuner.

I have never found a definitive answer on the legality in NZ of non-isolated radio and TV chassis back in the 1950s and 1960s. Some anecdotal evidence has them as illegal because they could not be earthed, but if so, it seems unlikely that Philips would have used the technique. Other anecdotal evidence suggests that they were frowned upon and even banned by some of the electrical supply authorities because they injected DC back into the supply. Of course, NZ got the “earthing instinct” as it were, very early on. Four-wire, three-phase distribution with multiple earthed neutral (MEN) was established as a national standard back in 1920. And the MEN system included the requirement that at each consumer drop, the neutral was bonded to a local earth by what is known as the “MEN Link”.

Turning to Pye, there is some evidence that Pye NZ had leanings towards American practices. I am relying upon memory here, but as I recall, at the beginning of the colour era in NZ, Pye offered clones of the Philips K9 model in the 22 and 26 inch screen sizes. Then about a year or so in, it released – with much fanfare – its “Vidmatic” 22-inch model whose main feature was its use of an in-line gun tube, of the RCA PIL type as far as I know. Another feature mentioned, although without much elaboration as to its benefits, was its use of a fet-based tuner (VHF-only in NZ at that time).

The use of mosfets in TV tuners was a very American idea the time, that is the mid-1970s. I think that the European setmakers were still using bipolar devices and would do for quite a while yet. (As best I can determine, the Japanese setmakers were somewhere in between.) RCA had been the first, in 1968, with a dual-gate mosfet VHF RF amplifier, although it continued to use its established cascode bipolar mixer for a few years. Zenith I think was the first to use a dual-gate mosfet VHF mixer in 1969. Whilst I have never discovered the origin of the VHF tuner used in the Pye Vidmatic, RCA would be a prime suspect as Pye NZ would have been dealing with RCA in respect of supply of the PIL tube. Circa 1975 RCA had introduced its KRK228 varactor VHF TV tuner. As well as a dual-gate mosfet RF amplifier, this had a dual-gate mosfet mixer in place of the previously used bipolar cascode. I am stretching the memory bank a bit here, but as I recall the Pye advertising implied that the Vidmatic tuner was fully fet, and not a hybrid, so the KRK228 (or a derivative thereof) falls into the “usual suspects” category.

Cheers,

GLENZ32 · 12th Apr 2019, 1:22 am

Thanks for that interesting information about some of the overseas connections with our local NZ TV manufacturing and our MEN earthing system Synchrodyne

So it would seem there were some Amercian based ties with Pye. I have a Pye Vidmatic CT102,103 & 104 in my colour TV collection, and two Philips K9's

Cheers.

SteveCG · 12th Apr 2019, 11:00 am

GlenZ32,

It is always nice to see a TV which has a turret tuner with channel 1 - a channel which required 'proper' aerials !

G6Tanuki · 12th Apr 2019, 11:33 am

Compactrons always fascinated me - they were, along with Nuvistors, the last desperate throw-of-the-dice by valve manufacturers in the face of burgeoning solid-state competition - and they really show what could be achieved with then-leading-edge valve technology.

Considering the devices used in TV front-ends, I could postulate that the early move to FETs (whether single- or dual-gate) by US-manufacturers/US-inspired rest-of-the-world designers was due to the greater number of TV stations in the US compared to the situation in Europe/Australasia. When there was a stonking great signal on every VHF channel [I remember Dallas/Fort Worth in the 1980s] crossmodulation performance becomes a major issue; if only one or two channels are in use, the front-end has a much easier life.

[Were Nuvistors used in any non-USA RCA TVs?]

9th Apr 2019, 1:51 am	#1
GLENZ32 Hexode Join Date: Apr 2008 Location: Wellington, New Zealand Posts: 289	Pye T25Y New Zealand B&W Hybrid TV Set Hi everyone, its been a rather long hiatus since I have posted or done anything with my old TV sets. The last time I posted on here was back in 2014. This was due to everything being put into storage in 2015 (due to major life changes) and have in the past 6 to 8 months relocated brought a house which has garage/s (so the lockup was cleaned out - what 'fun' that was) and a room off the side of one of the garages which I've turned into a workshop so projects and tinkering can take place again. So this Pye 19 inch set featured here is a hybrid model made here in New Zealand dating from 1969. Am uncertain if this is based on a British or Australian chassis/layout, someone here may recognize this as something familiar or a clone of a native model. These were a very common and came in a range of CRT sizes from 12 inch up to 26 inch. The chassis also went through some various changes over the years, the earlier versions were all valve, where as the later chassis like this one here had transistors scattered around the video drive & amplifier section and vision and sound IF stages and sync separator stages. The smaller sets also used a compactron in the fly back section, a 38HE7 which was the line output pentode & boost diode in one bottle. I acquired this TV which was back in the late 1990's. Back in 2003/2004 I made a half hearted attempt to get it working, found there were major issues with the vertical/horizontal so decided it was too hard at the time so put the thing back together and shelved it. 15 years on and I decided that for my first project in the new workshop was to resume repairing this and to get it working properly this time around. Upon applying some mains after its long slumber the set came to life displaying a crappy raster crackling audio and some arcing noise accompanied by hissing EHT which turned out to be the lead from the line output transformer to the top cap of the DY87 was about to fall apart. Once that was repaired and sorted I moved on to looking into the vertical to see what was up there. Discovered pretty quickly with the aid of the circuit that some idiot (not me) had in the past attempted to repair it by putting wrong value components in place not to mention a cap tacked across pins on ECL85 on the print side to try and compensate for whacked out frame operation which wasn't even meant to be there! So the putting the correct parts back in place and removing the bodged capacitor, all voltages around the valve measured right and the vertical was starting to look more normal again and height/linearity controls now worked properly! Moving onto the horizontal oscillator, the sync was poor and lock was very touchy and it didn't take long to discover that the phantom bodger had been there as well changing component values and linking things out again around the ECF802. I wonder what the logic behind doing this and obviously there was some fault that kept this person experimenting around with the circuit and the reasons why - who knows? Putting the right value components back in this area made things a bit happier and more stable and correct volatges were resumed and I could now obtain good horizontal sync and lock. With these two areas sorted I then focused on the resistors that were used in this model and several others. These mustard bodied types are notorious for going high ie 47k reading 70k, 100k reading 180K etc so I make a point of checking all of them and replacing and this was no exception as I ended up changing nearly all of them, I probably didn't have to due to tolerances within the circuit but as I have a 'ton' of NOS resistors and paranoid about old crappy resistors! Its more a piece of mind thing knowing that they've been done. I did leave one or two in there that weren't in any crucial positions and did notice slight improvement as I methodically put new ones in and tested the set in between. Once I'd done the resistor-rectomy, then removed the leaky/aged old can multi section filter capacitor and fitted replacements using three separate ones. Went through and replaced other old capacitors that looked a bit tired or were not reading right on the cap tester. Things were now starting to look quite good by this stage so I set about cleaning the case and the front panel/glass etc when the picture vanished...Hmm ok what did I do?? A bit of probing and it returned. Swing the chassis up - no picture, swing it down - picture! Turned out to be a poor solder joint on tag strip in the fly back area probably done by me as I did work on that bit in the past. Then the picture began to fade away at will now - what the heck! Glancing at the filament on the CRT it was dimming up and down. This was an intermittent break in one of the filament wires so fixed that and then the other filament pin terminal decided to break off on tube neck socket! This thing was starting to have a go at me. A few other things went wrong as they do put a wrong value resistor in and was greeted with magic smoke from it the moment I applied power, slipped with the meter probe and blew up the 2nd vision IF Bf137 transistor, burnt the side of my hand a little on the baking 38HE7 during a moment of being careless- man those things get super toasty hot! But not too many hiccups really. Once I had the set running stable, went to set the picture up using the test pattern and got it reasonably well adjusted there's a slight geometry error horizontally but not going worry about that after all its a 50 year old TV. The yoke correction rings have been adjusted to best as possible. So after all that and taking 15 years to finally fix this thing,we now have working usable TV! The photos don't do the image justice its bright, sharp with good contrast so the CRT is showing no signs of age at this stage. I'll run it over the next weeks to see if any further teething issues crop if but overall am happy with the outcome and feel a sense of achievement on this since it was probably one of the very first valve sets I decided to restore. I'm wondering about my next project for the bench...Hmm..it could be another Pye, I have a few of them! Thanks for reading my ramblings if you got this far. Enjoy the photos! Cheers Glen. Attached Thumbnails __________________ Visit my Vintage TV & Radio Page - http://nzvintagetvradio.blogspot.com/ Last edited by GLENZ32; 9th Apr 2019 at 1:56 am. Reason: Corrections

9th Apr 2019, 8:16 am	#2
linescan87 Heptode Join Date: Mar 2014 Location: Meath, Ireland Posts: 551	Re: Pye T25Y New Zealand B&W Hybrid TV Set Hi Glen, That's a cute tv and a nice little write up. Those resistors can be way out alright. Cracking crt. John Joe.

9th Apr 2019, 8:49 am	#3
dazzlevision Dekatron Join Date: Sep 2003 Location: Near Swindon, North Wiltshire, UK. Posts: 3,621	Re: Pye T25Y New Zealand B&W Hybrid TV Set Welcome back Glen. The cabinet style is very reminiscent of early 1960s Pye UK sets in moulded cabinets with cream coloured fronts, the VHF turret tuner and two rotary controls, such as the VHF/495 only 17” V220. See here: https://www.vintage-radio.net/forum/....php?p=1043708 There’s also the dual standard TV2: https://www.radios-tv.co.uk/communit...-sets-aquired/ However, the chassis bears no resemblance to Pye group UK mono chassis of the late 1960s.

9th Apr 2019, 9:25 am	#4
Hybrid tellies Nonode Join Date: Jan 2004 Location: 1966-1976 Coverack in Cornwall and Helston Cornwall. 1976-present Bristol/Bath area. Posts: 2,967	Re: Pye T25Y New Zealand B&W Hybrid TV Set What a nice looking set and its looking good. Very interesting write up especially seeing that it uses the E range of valves instead of the normal P range of valves. That combined line output/boost diode is also strange sight to our eyes, its quite amazing that the valve holder can deal with the high voltages present that we normally see on the top caps of the line output and boost diode valves. Many of us forget that in Australia and New Zealand they did not like using AC/DC techniques and most sets of this vintage used an isolating mains transformer. __________________ Simon BVWS member Last edited by Hybrid tellies; 9th Apr 2019 at 9:32 am.

9th Apr 2019, 9:53 am	#5
Synchrodyne Nonode Join Date: Jan 2009 Location: Papamoa Beach, Bay of Plenty, New Zealand Posts: 2,944	Re: Pye T25Y New Zealand B&W Hybrid TV Set Very true. Thus in this part of the world, E-series valves were normal (Everyday, if you like) whilst P-series valves were abnormal (Peculiar). Cheers,

9th Apr 2019, 11:56 am	#6
G6Tanuki Dekatron Join Date: Apr 2012 Location: Wiltshire, UK. Posts: 14,007	Re: Pye T25Y New Zealand B&W Hybrid TV Set Fascinating to see a Compactron in use. I don't think any UK-made TVs ever used them, they were almost exclusively a US thing.

9th Apr 2019, 7:55 pm	#8
mark pirate Dekatron Join Date: Mar 2008 Location: Worthing, West Sussex, UK Posts: 5,185	Re: Pye T25Y New Zealand B&W Hybrid TV Set Good to see you back again Glen, I also have not tackled a restoration for a while now, but hope to get back to the mountain of sets later this year. I agree that the front does look very similar to early 60's UK Pye sets, I have a 17" model in an all plastic case in the pile. The chassis has an american look to it, especially fitted with that Compactron, not sure it was a good idea to combine the line output with the boost diode though Mark

9th Apr 2019, 10:48 pm	#9
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: Pye T25Y New Zealand B&W Hybrid TV Set Information for the Compactron sweep tubes types 38HE7, 38HG7 and 37HK7. Line output pentode and damper diode in the same glass envelope. From Wikipedia, more information about the Compactron tubes: https://en.wikipedia.org/wiki/Compactron DFWB. Attached Thumbnails Last edited by FERNSEH; 9th Apr 2019 at 10:56 pm.

10th Apr 2019, 10:24 am	#15
1100 man Octode Join Date: Apr 2016 Location: Ventnor, Isle of Wight, & Great Dunmow, Essex, UK. Posts: 1,377	Re: Pye T25Y New Zealand B&W Hybrid TV Set Hi Glen, It's always fascinating to see TV's produced in other parts of the world- good write up too! First thing I spotted was the mains transformer which would be a very unusual thing to find in UK set. Series heaters, 'P' series valves and mains droppers were more the norm for us. The Compactron is something I've never seen before. I suppose on the face of it, it makes some sense to combine the LOP valve & efficiency diode, but it must get incredibly hot! Obviously on separate valves, top cap connections are used for the high pulse voltage connections. Having these on the valve base, I would have thought tracking on the valve base would have been a common problem. For sets using a mains dropper for the heaters, two separate valves require less power to be got rid of via the dropper, so the Compactron would not be attractive for UK manufacturers. I'm off to have a look at your website! All the best Nick

11th Apr 2019, 1:36 am	#16
GLENZ32 Hexode Join Date: Apr 2008 Location: Wellington, New Zealand Posts: 289	Re: Pye T25Y New Zealand B&W Hybrid TV Set Hi Nick, as I mentioned the majority of our sets were mains isolated, Philips being the only sets that weren't. The compactrons do get 'very' hot pays to keep fingers and other things well away when servicing these!! Amazingly the back cover isn't melted in where the compactron sits pretty much at the top of the chassis and a fair bit of heat radiates up. You'll enjoy my website, unfortunately I can't update it anymore won't let me login or change anything and I don't know why. Cheers Glen __________________ Visit my Vintage TV & Radio Page - http://nzvintagetvradio.blogspot.com/

11th Apr 2019, 3:18 am	#17
Synchrodyne Nonode Join Date: Jan 2009 Location: Papamoa Beach, Bay of Plenty, New Zealand Posts: 2,944	Re: Pye T25Y New Zealand B&W Hybrid TV Set Notwithstanding its monochrome receiver history, Philips NZ adopted isolated power supplies for its colour TV receivers, the first of which was the K9. Presumably the chassis was modified from the European original, which I think had a non-isolated supply. As far as I known the Australian version of the K9 also had an isolated power supply, as well as differing in having a rotary tuner. I have never found a definitive answer on the legality in NZ of non-isolated radio and TV chassis back in the 1950s and 1960s. Some anecdotal evidence has them as illegal because they could not be earthed, but if so, it seems unlikely that Philips would have used the technique. Other anecdotal evidence suggests that they were frowned upon and even banned by some of the electrical supply authorities because they injected DC back into the supply. Of course, NZ got the “earthing instinct” as it were, very early on. Four-wire, three-phase distribution with multiple earthed neutral (MEN) was established as a national standard back in 1920. And the MEN system included the requirement that at each consumer drop, the neutral was bonded to a local earth by what is known as the “MEN Link”. Turning to Pye, there is some evidence that Pye NZ had leanings towards American practices. I am relying upon memory here, but as I recall, at the beginning of the colour era in NZ, Pye offered clones of the Philips K9 model in the 22 and 26 inch screen sizes. Then about a year or so in, it released – with much fanfare – its “Vidmatic” 22-inch model whose main feature was its use of an in-line gun tube, of the RCA PIL type as far as I know. Another feature mentioned, although without much elaboration as to its benefits, was its use of a fet-based tuner (VHF-only in NZ at that time). The use of mosfets in TV tuners was a very American idea the time, that is the mid-1970s. I think that the European setmakers were still using bipolar devices and would do for quite a while yet. (As best I can determine, the Japanese setmakers were somewhere in between.) RCA had been the first, in 1968, with a dual-gate mosfet VHF RF amplifier, although it continued to use its established cascode bipolar mixer for a few years. Zenith I think was the first to use a dual-gate mosfet VHF mixer in 1969. Whilst I have never discovered the origin of the VHF tuner used in the Pye Vidmatic, RCA would be a prime suspect as Pye NZ would have been dealing with RCA in respect of supply of the PIL tube. Circa 1975 RCA had introduced its KRK228 varactor VHF TV tuner. As well as a dual-gate mosfet RF amplifier, this had a dual-gate mosfet mixer in place of the previously used bipolar cascode. I am stretching the memory bank a bit here, but as I recall the Pye advertising implied that the Vidmatic tuner was fully fet, and not a hybrid, so the KRK228 (or a derivative thereof) falls into the “usual suspects” category. Cheers,

12th Apr 2019, 1:22 am	#18
GLENZ32 Hexode Join Date: Apr 2008 Location: Wellington, New Zealand Posts: 289	Re: Pye T25Y New Zealand B&W Hybrid TV Set Thanks for that interesting information about some of the overseas connections with our local NZ TV manufacturing and our MEN earthing system Synchrodyne So it would seem there were some Amercian based ties with Pye. I have a Pye Vidmatic CT102,103 & 104 in my colour TV collection, and two Philips K9's Cheers. __________________ Visit my Vintage TV & Radio Page - http://nzvintagetvradio.blogspot.com/

12th Apr 2019, 11:00 am	#19
SteveCG Nonode Join Date: Jun 2009 Location: Herefordshire, UK. Posts: 2,495	Re: Pye T25Y New Zealand B&W Hybrid TV Set GlenZ32, It is always nice to see a TV which has a turret tuner with channel 1 - a channel which required 'proper' aerials !

12th Apr 2019, 11:33 am	#20
G6Tanuki Dekatron Join Date: Apr 2012 Location: Wiltshire, UK. Posts: 14,007	Re: Pye T25Y New Zealand B&W Hybrid TV Set Compactrons always fascinated me - they were, along with Nuvistors, the last desperate throw-of-the-dice by valve manufacturers in the face of burgeoning solid-state competition - and they really show what could be achieved with then-leading-edge valve technology. Considering the devices used in TV front-ends, I could postulate that the early move to FETs (whether single- or dual-gate) by US-manufacturers/US-inspired rest-of-the-world designers was due to the greater number of TV stations in the US compared to the situation in Europe/Australasia. When there was a stonking great signal on every VHF channel [I remember Dallas/Fort Worth in the 1980s] crossmodulation performance becomes a major issue; if only one or two channels are in use, the front-end has a much easier life. [Were Nuvistors used in any non-USA RCA TVs?]