PYE D18T Restoration - Recent Antique Fair find

[Atlantic 52]

Hello Guys,
In April 2016 I bought a very unmolested Pye D18T Console TV from a dealer at the Kempton Park Antiques Fair for a very good price. The set had obviously been stored in the dry and as a consequence the condition apart from some cabinet scratches is very good. Upon inspection only a few replacement caps could be seen inside. The mains smoother is dated Oct 1948. The tube is an MW22-14 and looks original. From my experiences restoring a D16T I recapped all of the 0.0015uF and 0.002uF HT decouplers and the heater decouplers. I also replaced some couplers and just about all of the wax coated caps in fact. Some electrolytics were either low, leaky or had no value at all! Anyhow, 44 capacitors, 2 resistors and a replacement EF50 line oscillator I got the set running once I found the sweet spots of the vision noise, vision sensitivity and brightness control. After some fiddling I got a very nice picture indeed, far better than I hoped. (see pictures) My main issues now are:1- Frame sync drift when warming up - you have to readjust a few times to keep lock. 2- I can't move the focus lever and don't want to break it! (any ideas how best to free it off?) 3- The three sliders already mentioned. Can these be repaired? They seem to have O/C wipers or nearly so. Is it worth trying to take them apart for cleaning?
Many thanks...

[brianc]

You were very fortunate with that set. The D18T is an attractive set and, as you have proved, capable of good pictures. The D18T and its smaller sibling the B18T are two of the post-war sets I have in my collection.

[Heatercathodeshort]

What a cracker! As Brian says you were very lucky with that one. The 18T series is capable of giving excellent results but the LOPT has become a weakness in recent years. It was released two months after my birth in 1948 so I have always had a soft for them.
We spent our teenage years together....Aghhhh! John.

[MonochromeMarc]

What a smashing set you've got yourself there, cracking picture too !
I've been after a D18T for a few years now but they always seem to elude me.

Marc.

[stevehertz]

I had one myself during my time of collecting VTVs, lovely, dinky little set. Sadly I never got around to getting mine going before I sold my collection. Re the warm up drift, I used to have a similar problem with the focus on a large Decca projection set. I often wondered if it would be possible to fit a negative temperature coefficient thermistor at some point in the circuitry in order to offset the effects of the warm up? I am not technically able, nor do I have a knowledge of the circuitry of the D18T to suggest exactly where this could be fitted, simply that the idea may work.

Two similar sets that I had were the Pye D16T and Ekco's TSC193, the latter that I did get working to a very high standard. See photos.

[Atlantic 52]

Many thanks for your messages Guys, its very satisfying seeing it work rather than standing idle for the last 8 months not knowing if it was any good at all. I had the brilliance slider out this morning and can see that some turns have broken so its not repairable unless it can be re-wound. I found a 10K ohm preset and soldered that in as a temporary bodge for now. I also had a lot of trouble with the height control so did the same with that. Does anyone know of a possible modern slider pot that can be fitted to allow at least easy adjustment even if its not exactly period?

[FERNSEH]

I know that many restorers of the B18 have substituted rotary controls for the sliders.
For weak frame lock your attention should be drawn to the Pye positive interlace filter circuit. Check or replace V2C (EB41) and the associated resistors R27B and R37B. If an oscilloscope is to hand check the sync pulse waveforms at the grid and anode of the sync separator V1H with particular regard to the eight broad pulses. C17A might be low capacity.

DFWB.

[thermionic]

Originally Posted by Atlantic 52

.......Does anyone know of a possible modern slider pot that can be fitted to allow at least easy adjustment even if its not exactly period?

Hello, Atlantic.

I have used 11 watt square section vitreous wire wound resistors to replace the open circuit sliders before. I gently crush the body of the resistor in a bench vice to reveal the wire wound element buried inside. This element is then used to replace the open circuit original.

It does need a bit of tweaking to get it right, but preserves the appearance of the set. A little bit of Vaseline on the new resistive element ensures smooth operation and a reliable contact.

Good luck with this, you have an excellent set there.


SimonT.

[thermionic]

Here is a link to one I made for a Marconiphone VC73 a few years ago. https://www.vintage-radio.net/forum/...3&d=1309372571

[Freya]

The cheap Chinese so called wire wound resistors are not the same and do not seem to contain wire strangely. I have used the same method as Simon using RS wire wounds, it works well.

[Atlantic 52]

Many thanks to you all especially Thermionic & Fernseh. I now have re-newed enthusiasm to have a go at the set once again. I like the wire wound resistor idea, I am now off to the garage to see if I have any 2K, 5K & 10K wire wounds I can crush in the vice!

[Atlantic 52]

Many thanks for your suggestions Fernseh ,
I had a go at the frame section and found 2 resistors that were high in value along with a poor capacitor. Refering to the 'Trader' service sheet 946/T5 I replaced R40, a 470K ohm resistor in line with the wiper of the frame hold pot which had gone up to 602K, R30 in the cathode of V8a, the interlace filter, had gone from 220K to 315K and C27 the coupler of 0.01uF to V9, the blocking oscillator, whilst reading 0.01uF on my tester had a resistance of just under 4Meg ohm on a meter. I bet it was lower with more voltage. The hold is now very much more solid in operation with no drift. A 3 hour soak test of the set showing films from my DVD player proved the repaired circuitry in that it didnt need adjusting at all.
The set has run well now but developed a sound fault in what seems to be V11, an EF50 that has gone noisy. Gentle tapping brings the sound back. Rocking the valve in its base doesn't make a difference. I tried to pull the valve out to replace it but its stuck fast. I guess I'll have to lever it's edge carefully. For some reason I have found that most of the RF stage EF50's are very well 'stuck' in their sockets.

[Boater Sam]

I have seen many EF50s that have had the centre pin glued into the socket!
I think it was done to overcome the poor pin connection with the socket.
Do you remember when the old TVs needed a bang on top to make them work?
This was the "cure"!

[brianc]

Be very careful when levering out the EF50. I did this in a pre-war Pye - yes, it was one of the 12C prototypes that should have been destroyed at the start of the war but this one escaped!! I had changed the valve holder for an RS Paxolin type as the original had crumbled somewhat. On levering the valve out with two screwdrivers, I pulled the centre of the valve base out and ruined it. There is a spring in the centre of the holder which grips the central spigot of the EF50 to ensure good screening. Well, gripping tightly is one thing but locking the valve in its holder for ever is another! So I opened the spring enough to allow easier removal.

[FERNSEH]

Hi Brian,
What do the pre war EF50 pentodes in the 12C look like? We know that the very first examples of this valve had those hooked pins. Also, I believe the early EF50 had a metalised coating instead of the usual metal screening can.

DFWB.

[Atlantic 52]

I had another look at the EF50 removal problem and in studying my set I see that some in the RF section have round spring steel retainers. (pictured) I thought great, all I need do is push the two sides down and then pull but it still won't come out. Maybe it is glued as well! I'll remove the spring clip around the valve centre pin spigot and see if that helps.
Does anyone know what the approved tool that pushes back the valve side retainers looked like in the good old days?

[Atlantic 52]

Hello Chaps,
One thing I meant to ask about on this set is the back cover tube end 'top hat'. On my set it has a very well made wooden cover painted brown to match the set. In study I can see that the rivet holes in the back cover for the more usual paper mache cover have not been used so it really looks like this set has always had a wooden cover. Has anyone else seen this feature? Could it have been that the usual paper mache ones werent ready in time for the early production sets?

[stevehertz]

To me, it looks like those rivet holes have been used. You can see compression of the fibre back around the holes where the pressure of the mounting has flattened the surface. So I'm guessing that the wooden cover is a home brewed replacement, very nice as it is.

[HamishBoxer]

Homebrew without a doubt note the wood colour inside also.

[Mikey405]

Hi Atlantic.

A "Weight-Watchers" sticky-toffee-pudding bowl makes a perfect sized rear top-hat for the Pye B18T - and if it can stand up to the heat of boiling-sugar then I think it will be perfectly good for the small amount of heat radiated by the Pye - although if it were mine I think I'd leave the original square one on.

Thanks Atlantic.

Kind regards.

From Mike.

1. "Before" back.
2. Sticky-Toffee-Pudding now eaten.
3. "After" back.