Members Set: Andrew Saunders
Manufacturer: PYE Chassis: 691 Model: CT72 (Hybrid) Year: 1969 System: UHF 625 line PAL single standard CRT: Mullard A56 120X |
Here is one of PYE’s early single standard ( 625-line only) hybrid colour television. This set is a unique example that was found by Andrew. He spotted it on e-bay and it came from Southend. Thankfully rescued from a house clearance and not taking a trip to the local tip like so many sets fate.
Photos Of How It Arrived
Then in Andrew’s own words:
I know the seller of the set had powered it up and had used a video to try it out. So, I briefly did the same with a DVD player and modulator. When tuned in and was astonished at what I saw. ( see below)
Is it really true? How can this be?
No doubt there are capacitors that are past their best, Callins for example, but look at the initial result… I have made no adjustments other than tuning, brightness, colour and contrast.
Indeed I think we can all agree that the resultant picture after initial switch-on is incredible. As most TV repairer/restores know, this just does not happen. What’s more from Andrews initial inspection, this set was still running on all its original components. This was starting to suggest the set might be been New Old Stock or bought and never used.
Andrew then picks up the story:
I changed a small electrolytic on the frame board as it was swelling at the rubber end and leaking, all others seem fine.
The pic below is the side flap removed and the convergence panel in the set-up position. Further inspection shows the date FEB 69 on two CCL caps. One on the CDA, the other in the line stage .
Time for a good inspection of the components in that stage….a resistor across the linearity coil looks over-heated.
This I’m sure you agree, is an interesting set and one that is shaping up to be a very nice example for Andrew’s collection. Now for a brief interlude and some technical information
I.F. Panel
Transistor |
Function |
Type |
VT1 | 1st I.F. Amplifier | BF196 |
VT2 | 2nd I.F. Amplifier | BF197 |
VT3 | 2nd I.F. Amplifier | BF194 |
VT4 | 3rd I.F. Amplifier | BF197 |
VT5 | 1st Phase Splitter | BF194 |
VT6 | 2nd Phase Splitter | BF194 |
VT7 | Sync Separator | BC147 |
VT8 | A.G.C. Amplifier | BC148 |
VT8a | A.G.C. Crossover | BC158 |
VT9 | A.G.C. Rectifier | BC148 |
VT10 | A.F.C. Amplifier | BF194 |
Decoder
Transistor |
Function |
Type |
VT12 | A.C.C. Amplifier | BF194 |
VT13 | Burst Amplifier | BF194 |
VT14 | Burst Gate Amplifier | BF194 |
VT15 | D.C. Amplifier | BC148 |
VT16 | Reference Oscillator | BF194 |
VT17 | Limiter Follower | BC148 |
VT18 | Line Phase Identity | BC148 |
VT19 | Colour Killer | BC148 |
VT20 | Chroma Amplifier | BF194 |
VT21 | Delay Line Driver | BF195 |
VT22 | PAL Bistable Switch | BC148 |
VT23 | PAL Bistable Switch | BC148 |
Colour Difference Panel
Transistor |
Function |
Type |
VT28 | Blanking | BC107 |
VT29 | R-Y Pre-Amplifier | BF184 |
VT30 | G-Y Pre-Amplifier | BF184 |
VT31 | B-Y Pre-Amplifier | BF184 |
Valve |
Function |
Type |
V6 | Luminance Output | PL802 |
V7 | R-Y Amp and Clamp | PCL84 |
V8 | G-Y Amp and Clamp | PCL84 |
V9 | B-Y Amp and Clamp | PCL84 |
Frame Timebase
Transistor |
Function |
Type |
VT24 | Frame Oscillator | AC127 |
VT25 | Frame Driver | AC128 |
VT26 | Frame Output Pair | BD124 |
VT27 | Frame Output Pair | BD124 |
Line Timebase
Valve |
Function |
Type |
V1 | Line Oscillator | PCF802 |
V2 | Line Output | PL509 |
V3 | Boost Diode | PY500 |
Transistor |
Function |
Type |
VT35 | Beam Limiter | BC108 |
Convergence Panel
Transistor |
Function |
Type |
VT32 | Blue Line Clamp | AC128 |
VT33 | Frame Clamp | AC128 |
VT34 | Red/Green Line Clamp | AC128 |
The CRT PCB
Back to the story of the set
we shall let Andrew pick up the events:
well it was too good to last…. ( see below)
Line hold had become weak and twitchy with slight bending at the top plus the hold control has to altered on channel change with a hard to lock picture. I tried a new PCF802 with no difference.
It looks like some proper fault-finding is now required and I will start to check the oscillator circuitry around the discriminator diodes and PCF802 voltages etc.
Let the fun commence….
A 100k in series with line hold control was completely O/C.Replacing it cured the fault. All other components checked out ok.
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 I don’t want that happening in this set !
So, in this case, prevention is better than cure.
And some final words from Andrew
I think this is an important piece of history, not just because of its near perfect cosmetic and operational condition, but mainly because it is an example of one of the first single standard UHF colour televisions to be released in the UK.
In my humble opinion, it gives an excellent picture and is easy to service and adjust. A good uncomplicated design. I Hope this is of interest to the readers at Radios-TV, please feel free to leave comments below and I will respond if any more info is needed.
Kind regards, Andrew.
nice looking tv set and the photos are very good
That’s certainly in tip top shape. Nice one !
We sold these and I installed and fixed them, I liked them, easy to repair and as reliable as any other sets perhaps better.
Good picture, I think the CDA helped that rather than the early RGB drive sets, i.e RBM A823. The mechanical tuner gave me less trouble than the later varicap push buttons and Mullard 1043 tuners used I think it was the 693 variant.
Frank
A corking set and what a great find especially in that condition, well done that man !
That is unbelievable such a good colour pic and in such mint condition
well done
Thanks for all the feedback everyone.
It goes to show just how capable these early sets were at producing good pictures and how time and usage was their biggest enemy.
Needless to say, I don’t use this set very often, just an hour or so every few months.
Hi,
Great to see pictures and images of the very first family colour television, purchased around 1970. I used to get into trouble from my dad for fiddling with the hidden controls to adjust convergence and colours within the left-hand side, screwed side panel. In the day, the TV was prone to become unaligned, so I experimented realignment using the famous ‘Test Card’ etc. I had seen the TV engineer when on occasions he was called upon using the panel…
The TV rarely had any problems, other than my mucking about with the ‘hidden panel. I always put it right, and became a dab-hand at electronics and the like at the tender age of 12.
Best Regards
David
Excellent set! I didn’t see too many of these when I started Philips but the ones that did come in were easy to fix and gave excellent results. It’s full of Mullard ‘Mustards’ so probably not even worthy checking them. Great job….it should go on for many more years.