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Old 26th Dec 2019, 2:18 am   #1
beery
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Default Queen's Speech challenge 2019 (failed!)

Hi all,
I decided to give myself the challenge of restoring a scrap TV22 chassis to watch the Queen's speech on. I only started on the night of December 23rd, so I did give myself rather a lot to do. Anyway, I didn't quite get there.
Here is the journey so far...

To start with I had the remaints of the TV22 that Fernseh had rebuilt with a Thorn 1500 lopty. It had no speaker, no tube and no RF unit.

Then I found a scrap MK2 RF unit, so I started on this. Several parts had been robbed as well as the valves.
First I removed the Band III adaptor, which was in a very poor state and had lost its bakelite cover.
Then I replaced all the waxies, some of which were missing.
I then modified the unit to work with a MKI top deck and fitted a set of second hand valves of unknown condition.

To be continued...
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Old 26th Dec 2019, 2:45 am   #2
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Default Re: Queen's Speech challenge 2019 (failed!)

What a great idea! Can you reset the deadline for next year? It was a good speech, so I hope you caught it on another television. A little oasis.

It seems like you got rather a lot done anyway!
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Old 26th Dec 2019, 3:14 am   #3
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Default Re: Queen's Speech challenge 2019 (failed!)

Hi all,
the saga continues...

I managed to find a set of scan coils after much searching.
I fitted a new speaker.
I then plugged the RF unit into the set, shorted across the CRT's heater connections and powered the set up to see what would happen.

After a very long warm up I could hear a healthy line whistle.

I then found an MW22-14 in my parents loft. I fitted it, crudely fitted on a new CRT socket and fashioned a tube clamp from solid cored wire.

I plugged the set in and was greeted no raster. I shorted the grid and cathode of the CRT and the screen lit up brightly.

Now most of the waxies on the top deck had already been replaced by David (Boynes), but the few remaining ones were giving trouble.

I replaced the CRT cathode coupling capacitor, the CRT grid decoupling capacitor. I also replaced the 56K resistor in series with the brightness control, which measured 85K, with a 47K (note this is a compromise as this resistor is 39K in the MKII chassis).

Now I was rewarded with a very dim raster at maximum brightness. I could get interference on the sound, but nothing on the screen.

At this point time was up. My brother had arrived to stay in my old TV room, so I could not work there after that. By this time it was late on Christmas eve.

I removed the RF unit for cold checks and noticed that a few resistors were missing. The screen feeds to the final vision IF and the video output were missing as was one of the resistors in the sound AGC.

I was then able to receive sound with lots of RF hiss and see something on screen. However things were clearly not right as there were no syncs and the line timebase had gone up in frequency somewhat.

Well it was time for lunch and then the Queen, so time ran out.

I shall continue though...

Cheers
Andy
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Old 26th Dec 2019, 7:57 am   #4
dave walsh
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Default Re: Queen's Speech challenge 2019 (failed!)

Impressive, amusing and informative all in one package Andy. I suppose it's the opposite of the late and much missed Chas Miller's "Concourse de Elegance" competitions. We will look forward to part two of your TV22! At least you knew that it was a 3pm deadline. I can think of one person who would have thought he needed to get it done by the morning. Why not give yourself a break and aim for New Year's Day now?

I might be making this up but I seem to recall that someone else set this kind of goal previously and got there but I'm not sure if it was around Xmas? That doesn't diminish your achievement however. It reminds me of the CH4 program "Scrapyard Challenge" in which contestants had to assemble some kind of vehicle from "found" components. Perhaps it will catch on within the retro electronics field. There is often discussion on here about the difficulties of presenting technical subjects to the "general" audience but I suppose the higher voltages might preclude that, on broadcast Television anyway in case someone decided to dive in with a live chassis and/or a LOPT etc.

There is a bit of a parallel with the more recent CH5 series in which Railway Modellers worked against the clock but I was a bit conflicted about that as the technical side was good to watch but overall the presentation seemed a bit stereotypical. Of course James May [Mr Marmite] takes the reverse [engineering] approach in the disassembler programs [a la Hunikin] but that's fascinating like your efforts. I can think of another person who seems to be able to sort out a radio or TV in the blink of an eye and think nothing of it but I wouldn't want to embarrass him and his three initials
I hope that you and everyone else have had an enjoyable Christmas so far.

Dave W
Bexhill


It's finally stopped raining for a while, down here in the tropics, so my thoughts are with anyone who may have been, or is still, under threat from the weather

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Old 26th Dec 2019, 10:53 am   #5
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Default Re: Queen's Speech challenge 2019 (failed!)

Quote:
Originally Posted by dave walsh View Post
Impressive, amusing and informative all in one package Andy. (
Absolutely! ..and so near. I think we would allow you finish it and show us a recording of the Queen's speech.

Peter
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Old 26th Dec 2019, 1:25 pm   #6
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Default Re: Queen's Speech challenge 2019 (failed!)

That was a bold attempt, you did pretty well getting a raster on the screen in the short time frame !
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Old 26th Dec 2019, 2:10 pm   #7
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Default Re: Queen's Speech challenge 2019 (failed!)

Quote:
Originally Posted by dave walsh View Post
I can think of one person who would have thought he needed to get it done by the morning.
Didn't the Queen's Speech use to be broadcast on the radio in the morning, and on the television in the afternoon?
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Old 26th Dec 2019, 3:31 pm   #8
dave walsh
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Default Re: Queen's Speech challenge 2019 (failed!)

Yes I think you may well be right about that Julie-I'd forgotten!

I was though, in fact, just making a quip about a certain well known personality who claimed recently that he sometimes watched it.... in the morning-impossible! I will say no more, as others may be tempted to break a basic Forum Rule which could ruin the overall mood.

Dave W!
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Old 26th Dec 2019, 7:11 pm   #9
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Default Re: Queen's Speech challenge 2019 (failed!)

Hi all,
thanks for your encouraging replies.
I should get a bit of workshop time after my brother goes back. However, the noisy audio does not bode well as I realize that I have left no RF generators at my parents house, I really should send one back from my home.
Any line timebase problems could also be a challenge as it is a real mixture using the original scan coils, width and linearity controls married with a Thorn 1500 series lopty, a bespoke tripler and a blocking oscillator circuit using 1500 components. The triode section of the ECL80 is used for the blocking oscillator and a PY83 was added as the boost voltage is too high for the PZ30.

Quote:
Originally Posted by dave walsh View Post
I might be making this up but I seem to recall that someone else set this kind of goal previously and got there but I'm not sure if it was around Xmas?(
Hi Dave,
Yes it was Fernseh, who was restoring a Thorn 2000 a couple of years ago.

Cheers
Andy
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Old 30th Dec 2019, 12:33 am   #10
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Default Re: Queen's Speech challenge 2019 (failed!)

Hi all,
success at last!

With a chance to work on the set again, I set about replacing the last waxies on the top deck, which included a few around the sync separator.

I then powered the set up to see what I could get.
Again weak sound with plenty of sound on vision.

I found some much better looking EF80s and set about swapping them one by one, which flushed out a couple of low emission ones.

Now, remember that both my RF generators are not at my parents' place, only an Aurora, so time for extreme measures (I'm using trader sheet 1091 for component references)...

Unscrewing L4 fully and screwing it in for peak response gave me lots of gain.
Still sound on vision was to the point where you could not see the test card.
I wanted to adjust sound trap L13, but found the slot in the core rounded off. So I unscrewed the core of L12 (above L13) and then removed the core of L12 from the top, swapped it for the core of L12, screwed it downwards somewhat and fitted the damaged core for L13 with the good end uppermost.

I could then set L12 for maximum sound and L13 for minimum sound on vision.
The results are now ok, but the gain is massive and the bandwidth a little low, suggesting that the RF chassis may have been fringe tuned.

The line linearity is generally ok, but there is a massive foldover on the left-hand side, indicating that the flyback is slow. I wonder if Fernseh can confirm if this is how bad it was back in the day or if there is something wrong in the line output stage.

Having missed the Queens Christmas message live, I had to go for a recording. I do think the camera makes the queen look a lot younger

Cheers
Andy
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Old 30th Dec 2019, 8:26 am   #11
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Default Re: Queen's Speech challenge 2019 (failed!)

Clearly the band-pass characteristics in the video IF are off, but hey, great job getting it working from the starting point you had. It just goes to show what can be achieved in an emergency situation, to get a set working and see a sensible image.

Once you have swept the IF and aligned it for the correct characteristic, sorted out the damping and left sided linearity issues, it will look "sharp as a tack" and like an image from a BBC studio video monitor from the 1950's era.
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Old 30th Dec 2019, 10:38 am   #12
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Default Re: Queen's Speech challenge 2019 (failed!)

Andy, I'd never thought of reducing the video bandwidth as a means to eternal youth but you've certainly reduced the Queen's wrinkles. Well done!

Peter
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Old 30th Dec 2019, 5:26 pm   #13
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Default Re: Queen's Speech challenge 2019 (failed!)

Great progress so far, reading this makes my wonder if I could do a similar thing with a scrap TV24.
It has an o/c blocking transformer, no LOPT and a few missing valves.
I have a scrap HMV 1807 chassis that could donate a good LOPT, and I am sure to have a couple of transformers that may work as blocking TX.

I always fancied knocking up a Frankenstein set!

Mark
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Old 30th Dec 2019, 6:20 pm   #14
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Default Re: Queen's Speech challenge 2019 (failed!)

You might be able to salvage some parts from the cheaper, plastic-cased TV22!
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Old 30th Dec 2019, 8:33 pm   #15
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Default Re: Queen's Speech challenge 2019 (failed!)

Brilliant write up (from someone who finds vintage TVs scary and baffling!)
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Old 30th Dec 2019, 9:14 pm   #16
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Default Re: Queen's Speech challenge 2019 (failed!)

About time I entered into the discussion because it was me who created the Frankenstein TV. That was one Sunday afternoon in 1985 or was it 1986? It was a long time ago.
The line output transformer had failed and a replacement wasn't to hand. However, I spotted an ex-rental Thorn 1500 on the scrap pile, perhaps the jellypot line output transformer could made to work in the TV22? Also removed from the 1500 was the line blocking oscillator transformer.
The oscillator transformer was fitted first, fiddled about with component values so that oscillator will work at 10,125c.p.s.
Next, mount the jellypot on the chassis. Fit a valveholder for the PY800 boost diode, I didn't trust the H-K insulation of the PZ30 for the task in hand.
After everything was connected up a diode was connected to the LOPT's EHT connector in order that the EHT voltage can be measured. Just over 3.5KV. A doubler will provide the correct final anode voltage for the CRT. The doubler consists of three BY182 silicon diodes and two 0.001microfard capacitors. The components were assembled on a modified group board.
Well, amazingly the thing actually works. Make no mistake there was nothing especially clever about the line output transformer substitution, but somehow I got away with it.

I'm delighted that the set is in good hands and being restored to working order again.

DFWB.
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Old 31st Dec 2019, 12:07 am   #17
beery
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Default Re: Queen's Speech challenge 2019 (failed!)

Hi David,
That's quite an achievement for a Sunday afternoon.
Can you remember if the foldover was that bad at the time or is there a fault?

Hi Peter,
Yes you can't see the wrinkles, but then l cheated. The recording is from the first royal Christmas TV broadcast in 1957. The Queen was saying something about the problem of unthinking people who want to throw away the things of the past. I'm sure she was complaining about people who want to throw away old tellies of course!

Cheers.
Andy
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Old 31st Dec 2019, 1:15 am   #18
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Default Re: Queen's Speech challenge 2019 (failed!)

Hi Andy,
I'm sure there is a fault because I remember demonstrating the set in the shop and it received favourable comments about the picture quality. It might be a good idea to check the waveform shape at the grid of the line output valve. The foldover might be a result of the flyback time being too long or perhaps there is a fault in the energy reclaim circuit.

DFWB.
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Old 8th Jan 2020, 2:49 pm   #19
beery
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Default Re: Queen's Speech challenge 2019 (failed!)

Hi all,
I did start tracing out the timebase circuit and will need to understand it all before I can fault find it. I have the BRC1500 circuit to hand and will scan it in as a guide.
I think December the 29th was the last time I had the chance to look at the set.
It will be Easter before I can look at it again.
I might before then have time to look at making a few bits for it like the focus lever, the front tube clamp and maybe some new wooden feet.

Not sure it is all worth it though. I have a spare cabinet with holes in it. I wondered about filling the holes with fibreglass and then spraying the case ivory?? No back either of course and I would certainly not give it away with one of my lovely spare tubes in it!

Anyway, I think I will start by making a gerber file for the focus lever...

Cheers
Andy
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Old 8th Jan 2020, 7:15 pm   #20
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Default Re: Queen's Speech challenge 2019 (failed!)

Hi Andy,
link to the Biffa bin TV22 restoration job of May 2014. The back was made from a salvaged TV24 back, same width as the TV22 but needed cutting down to size height wise.
https://vintage-radio.net/forum/show...=105828&page=4

With regard to the picture foldover at left side of the picture.
It might be possible that the line oscillator is locking on to the trailing edge of the differentiated sync pulse. The line sync coupling capacitor should be connected between the two anodes of the ECL80 sync separator and line oscillator valve. A small value capacitor is required for the correct differentiation function.

I can have a brass CRT securing band made for your set.

DFWB.
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