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1974 PYE CT203/1 - Hybrid 697 Chassis

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crustytv
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Well curiosity got the better of me, the CT203 kept goading me.........

I gave the set a once over checking wiring and components for signs of distress I wondered if there might be some horrid Callins hiding somewhere waiting to biff me in the face but none were to be seen. As nothing looked outwardly wrong I fitted a plug and powered it on, ready to pull the power at the slightest whiff of trouble.

Very strange as I'm used to listening for the 10,125Hz line whistle but nothing with these 625 sets. I heard the speaker crackle and the wonderful warm glow of the Valves showed life was breathing in there again. Looked around the front, a faint glimmer on the screen, turned the brightness and contrast and I was greeted with a full raster, albeit a rather green looking one.

Typically we have only just lost analogue so I decided to hook up the RF out from my Sky box. Twiddled the BBC1 tuner, after a while there was the picture, slightly de-focused and not a lot of colour with the frame running through. I have not located the frame hold yet, I need to familiarise myself with the set and the schematic.

I have to stop here as I know I will get caught up and I cannot let that happen. The main exercise was to see if it would give first light and what faults it would reveal, well I've not been disappointed.

Look forward to getting bench time in a month or so and continuing the journey and this story.

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Posted : 09/10/2012 2:45 pm
malcscott
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Looking good Chris, the frame hold has a knob on at back off set. I would snip off the mains filter cap.

 
Posted : 09/10/2012 3:07 pm
crustytv
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I normally would have snipped it Malc but I was in "gung-ho-mode". I will do so when it eventually makes it to the bench but as I say that is going to be a while, after the move.

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Posted : 09/10/2012 3:10 pm
sideband
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Hi Chris.

Be prepared to arm yourself with a supply of PCL84's and PL802's. The PL802 is luminance (video) amp and the PCL84's are colour difference amps with the triodes as clamps I think. There was a solid state version of the PL802 (PL802T) which just plugged in but I don't suppose you want to replace a nice glowing valve with a lump of silicon.....!

Haven't checked but there are probably plenty of PL802's about.

Oh yes....beware that 25kV bites! 8))

Rich.

 
Posted : 09/10/2012 4:37 pm
Anonymous
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How much is EHT on a prewar mains EHT? 1.5KV and too much current?

I imagine the PL802 survives the odd flash-over better than Silicon. The sets designed for Silicon have two types of spark gap (one looks like a capacitor, the other is PCB layout), special earthing layout, special CRT base layout and probably other "protection" too.

 
Posted : 09/10/2012 4:50 pm
malcscott
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Plenty of nos PCL84/PL802/PL802T in stock here :aad

 
Posted : 09/10/2012 5:08 pm
malcscott
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Chris, i have found a full service manual for your Pye set.

 
Posted : 10/10/2012 11:21 am
crustytv
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Wow! Malc, you must have read my mind I was hunting through my library last night, I've got loads of colour set manuals but not the CT230 which is typical. All I had was the R&TS which would have sufficed but the manufacturers data is so much better, especially the setting up procedures for static & dynamic and all ther oddities I'm going to be introduced to.

If I could borrow that I would very grateful, I can scan it for the online library.

Regards
Chris

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Posted : 10/10/2012 11:40 am
malcscott
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No problem

 
Posted : 10/10/2012 11:51 am
Anonymous
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the frame hold is the one that sticks out of the pannel next to the big line pannel.
please note you can unplug the colour drives from the cda pannel one at a time or even swap them round to prove tube or cda fault it looks like red is missing also note the rgb a1 controles on the convergence board. good luck with it a very good set to start with.
rob t

 
Posted : 10/10/2012 12:01 pm
crustytv
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Found a picture of what the PYE would have looked like with its legs. If I cannot source a set at least I know what they look like to have a go at making some.

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Posted : 10/10/2012 9:41 pm
Anonymous
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The 3 pcl84's have a socket by the side of them one for each colour, simply unplug the green and blue and then see whats on the screen, if nothing plug the red lead into say the green . If you now have a red picture the fault is on the cda panel, most likely the red channel 12k anode load.

If there is no red replace all the plugs in there right sockets, then on the tube base check for A1 volts to the red gun this voltage comes from a control on the convergence panel. For the frame faults the electrolytic's on the frame panel are suspect.

You will grow to love these sets. It was common to fit a pl802t but the picture never looked as good.
rob t

 
Posted : 15/10/2012 4:51 pm
crustytv
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Cheers Rob, thanks for the tips, I must get over to Malc and get the manufacturers service manual too.

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Posted : 15/10/2012 5:07 pm
crustytv
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Some may like it, others may hate it, when starting a new restoration it's been customary for me to dust down the TickTock Time Machine, (TTM) set the controls for the intended destination and see what was going on at the point in time. I forgot to do that, so here we go, ready for the ride? Those who lived it might find the mental images too traumatic............................. :aal

Arriving in 1974 I find my attire is somewhat embarrassing but at least I will fit in. Starting with the 6 inch heels on my brown, orange and green platforms. Followed by a rather fetching pair of green Oxford Bags, an even more interesting maroon shirt with round collars dumbo would be proud of and finally.... Oh the shame, a knitted tank top. A glance in the mirror and I see the TTM has provided me with a rather large set of sideburns too.

The house! well 2" turquoise shag pile looks like it needs a comb. I seem to have a black PVC settee with orange cushion covers and curtains with massive orange and brown flowers. Meanwhile over in the corner is the obligatory 70's home bar, complete with Cinzano, babycham, a Party Seven, Pineapple Ice bucket and Tupper-ware bowls with cheesy footballs. The one sight that greets and gets me all excited is the brand new rented 19" Decca....... drooool. :aag

I can't resist so switching it on I get to see what's happening in 1974.

Abba have just won the Eurovision in Brighton and their winning song Waterloo has just hit number 1.

News events :-

  • The Terracotta Army Unearthed[/*:m:lse932xk]
  • Nixon Forced to Resign[/*:m:lse932xk]
  • Lord Lucan Disappears[/*:m:lse932xk]
  • IRA Bombing campaign of Britain underway[/*:m:lse932xk]
  • Resignation of Mr Heath's Administration[/*:m:lse932xk][/list:u:lse932xk]
  • At the movies

    • The Great Gatsby[/*:m:lse932xk]
    • Towering Inferno[/*:m:lse932xk]
    • EarthQuake [/*:m:lse932xk]
    • Blazing Saddles.[/*:m:lse932xk][/list:u:lse932xk]
    • Then all of a sudden the TV flickers, along with the lights and I'm plunged into darkness........ Yep its the enforced three-day working week as Edward Heath's government attempts to preserve dwindling fuel supplies, a result of severely fractured relations with the miners.

      Oh well it was fun but back to the future and the bench...........

      I decided to select my autumn & winter projects and decided I would take on two sets in parallel. One will be the CT203/1, the other a B&W, I've not decided yet on the B&W.

      I've delayed this PYE for almost a year I've had my head stuck in the Mazda and Mullard books but nothing more is going in, I need to get hands on so now time to make a start.

      This set is so damned heavy, It resided in the TV display room at the front of the house it took me four hops to get it to the workshop then one final push to get it on the bench. Phew! Good news is I built the bench with this set in mind and I'm glad to say it holds it fine, no bowing at all.

      If you remember I just gave this set the full beans last October and a raster was obtained, albeit a rather green one. As a further quick test I fed in a SKY RF feed and it showed the IF was fine. See post #1 for those pictures.

      So today I thought lets have a look around and try and determine what's what. As you know until now I've just been working on B&W sets and have become familiar with recognising the various stages, for me this is a whole new ball game. Obviously the Power supply is easily recognised but then it rapidly becomes a head scratch, luckily I have the full service manual for the 697 chassis so I will be using that as my road map.

      I found a couple of interesting things one a resistor blown in half (see last pic) which is mounted on the metal shield. This did not happen when I powered it on last time so must be an old fail, obviously the set continues to work with it missing, I will have to figure out what function it serves.

      The other oddity is a mains flex attached to the on off/vol switch which is doing absolutely nothing the blue and brown are just floating and taped up at the other end (see pic 3&4 ). A red wired from the pot goes into a one of those block connectors and fly wire from that goes up to a cap on the shield which is in series with the blown resistor.

      It's not remnants of an old main input as the original is still there connected to the PSU. I just this minute did a test, pluged the set in and operated the on/off/vol switch, it functions as expected. What the mystery wire that does nothing is, is exactly that, a mystery. I will remove it but make note of how connected in the unlikely event I will need it.

      I need to locate the mains filter and snip it out as I don't want to risk that exploding and causing damage to the set or my nerves then set a plan of action. I think I will also have a sniff with the leader and see what the CRT tells me emission wise, and figure out the issues presented last time I had first light.

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Posted : 25/09/2013 3:06 pm
sideband
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I don't think that's a capacitor! More likely a PTC resistor. May be degaussing but not sure. Sometimes there is a shunt resistor in circuit and if the PTC fails, all the degaussing current flows through the resistor which objects very strongly.... :aac

You may have to use your new degaussing coil to manually degauss.

Rich

 
Posted : 25/09/2013 3:17 pm
malcscott
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The blown resistor forms part of the degausing cct. 680 ohms rings a bell. The set will work without it, but the colours will be impure.

 
Posted : 25/09/2013 3:19 pm
sideband
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680 ohms rings a bell.

That's it! They go with a hell of a crack when several 10's of amps get shoved through them.... :ccf

 
Posted : 25/09/2013 5:02 pm
crustytv
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Yep Auto degauss. So is it likely R302 Thermistor which was the cause, interestingly it is not listed in the parts section, I had a look through some " Television" articles and found the following generic description of a degaussing circuit for colour TV, it specifically mentions the VA8650 (Mullard).

Television Extract
The heart of present degaussing circuits is the Mullard VA8650 (or equivalent) thermistor. This has a positive temperature coefficient, with a cold resistance of 80R +/- 20%. As the thermistor heats up the resistance rises very considerably above this of course. When operated across a 240V mains supply the lower limit value (80 - 20% =64R) necessitates a series resistance of 80R to limit the maximum peak current to 2.6A

The network below R605 in the circuit (see Fig. 1) must therefore appear as 80R at switch-on. Thus with the shunt 680R (R606) in position the resistance of the v.d.r. (VDR60l) plus the coil pairs must appear as about 90R. The actual coil current flowing will then be about 2.3A. The 33V/l00mA v.d.r. (VDR60I) with this current passing through it will have a resistance of about 43R so the coil resistance (total) must be about 50R. At switch-on the thermistor is cold and the voltage across the network of the v.d.r., coils and R606 will be high (an r.m.s. voltage of about 240 / 2 =120V). The current through the v.d.r. and the coils is high (2.3A) therefore and the magnetic flux produced is sufficient to saturate the area to be degaussed.

The current flowing heats R605. As a result its resistance increases and the voltage across the lower network decreases. As the voltage decreases the current falls and the resistance of VDR60l increases to reduce still further the current through the coils. A permanent small current flows through the 6800 resistor (R606) but a switch-on/stable current ratio through the coils of about 2,000: I is obtained. The exact ratio depends on the ambient temperature conditions around the degaussing components. The coils must have a resistance of about 25R.

VA8650 thermistor, v.d.r., 680O resistor, tag strip and pair of 50O (total) degaussing coils (state tube size).

Supplier: Manor Supplies, 172 West End Lane,London, N.W.6.
Price £2.30 including post and packing. Shop price to callers is reduced appropriately.

Pack also available from Forgestone Components, Ketteringham, Wymondham, Norfolk.

All that for £2.20 !!! them were the days A!

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Posted : 25/09/2013 5:16 pm
Refugee
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That resistor would be enough for the original owner to retire the set as the symptom would be purity errors that look like a tin of paint has been thrown at it. Last time I had VGA screen in like that a new thermistor was enough to clear it all up without using a manual coil.

 
Posted : 25/09/2013 5:34 pm
Tazman1966
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Hi Chris.

Nice to see this old beast getting its turn! I'm pretty sure that the mains filter cap is located on the front control panel. It's usually one of those grey Plessey branded caps...

I'll be following this one with pleasure :)

Tas :qq1

PS: There's a novelty, the line hold knob is still there. They often fall off and disappear never to be seen again!

 
Posted : 25/09/2013 5:55 pm
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