Bush TV22 Mk2 - first approach using a variac

[Helder Crespo]

Hello everyone

Thank you so much for your time and all the valuable information! I will take all of it into account when I start doing more serious work on my set (I'll print this thread and highlight all key points for reference).

Given the relatively low technical level involved in a global recapping (it requires mostly time and attention, as I will be replacing the waxies and electrolytics one by one, probably using the spare tags whenever possible), I will do this prior to plugging it to the mains.
Even if the LOPT and/or tube turn out to be dead in the end, this will not prevent me from pursuing the goal of bringing the TV back to life, as I really like this set, its beautiful exterior design and cabinet, and its history. Which is why I got it in the first place. Mine has an interesting recent story too. It was used as a prop in a 2016 documentary (3 episodes) about the Ealing Comedies, hosted by Richard E. Grant (I got the set directly from the director), and it got a few seconds of screen time, where the host actually turned it on (thanks to the miracle of special effects). I recently found the documentary in a Chinese video sharing website (I can provide the link if anyone is interested). Due to the unique bakelite pattern in each TV22, I could confirm that my TV set was actually on TV.

Helder

p.s. - if anyone has a component list for all waxies and electrolytics that you're willing to share, this would be most helpful. Otherwise I'll prepare one from scratch based on the schematics (Trader Sheet, etc.) that I have, but I imagine that many of you may already have prepared such a list.

[Helder Crespo]

Originally Posted by Argus25

Sounds like you landed a great set.
In the case of the LOPTY, if pitch coated and you can see cracks extending down to the overwind, I would not power that until the pitch was dissolved away and the Lopty varnished (there are other threads about doing this)

Over my last weekend in London, I did a quick visual check on the LOPT.
Looks pretty good, I guess, at least compared to others I've seen so far, and the cracks seen on the top part of the pitch do not appear to extend down. Didn't check the continuity/resistance of the windings as I would have to remove the can and didn't have time for this. Instead, I used my time to finish a basic restoration - recapping, speaker, mains wiring and cabinet - of the DAC90A that I bought after the TV22, in part to practice prior to tackling the TV22). Nevertheless, I did check the frame oscillator transformer, and it read ok: very close to 540 ohm on the primary and 480 ohm on the secondary.
Here are a couple of pics of the LOPT and tube as they are now (so far I've only done a basic dusting with a vacuum cleaner and brush). I would appreciate if you spot something I should take a better look at at this stage.

[mark pirate]

Your set looks to be in good shape, the fact that the frame blocking transformer checks OK is a sign that the set was not subject to damp storage.
The LOPT looks good as well, although I would recommend passing a current through the overwind for a few days to drive out any moisture that may be present.
Looks like it should be a straightforward restoration.

Mark

[Argus25]

Originally Posted by mark pirate

The LOPT looks good as well, although I would recommend passing a current through the overwind for a few days to drive out any moisture that may be present.

Mark

I don't know that I would agree with that.

It is interesting to look at the photos.

As you can see where the heat had been rising near the top of the transformer, more of the lower molecular weight hydrocarbons were driven out of the pitch. Hence the hardening and volume shrinkage causing the cracking there.

Mostly the over-wind area pitch looks better, however, if you look at photo 3 it is easy to see the pitch has failed and there is a crack, likely extending to the overwind surface. This is how the moisture gets in of course, it is analogous to a "failed seal". While you could drive some moisture in one direction with heating, as soon as it cools, water vapor is heading back in there again isn't it ?

I would not even consider powering a Lopty like this until that risky situation had been resolved, or it is encouraging failure of the transformer.

The better move is to dissolve the pitch and replace it with multiple varnish dips as I had recommended on other threads, or a new pitch coat if one wanted to keep it original as somebody else had done.

Of course, you might seem to "get lucky" with a lopty like this, power it and all seems well, apparently vindicating a theory that it is ok to run a lopty with cracked pitch like this, but in my view failure is just around the corner.

[Argus25]

......another thing I would do if this was my set. Replace the old EHT cable and the rubber grommet in the EHT cage wall, its easy to get good EHT cable from a defunct color TV lopty, usually that stuff is well over 20kV rated.

Notice the area where the EHT cable is touching the external aquadag on the CRT, likely a place for the old EHT wire's insulation to fail.

Also, if you remove the EHT clip from the anode cap on the bulb, to solder a new EHT wire on, be very careful as the clip can be corroded onto the cap on the bulb and the friction trying to remove the clip can cause the cap to separate from the CRT breaking the feed through wire. So it might be necessary to spread the halves of the clip a little first.

I would also recommend getting an EHT clip with some insulation over it, there were some nice red ones made by Bulgin with that sized clip.

[peter_scott]

It's easier to measure the EHT with the naked connector but I must admit that I got bitten on three occasions when working on my TV22 recently. I hasten add that I'm nothing like as cavalier when working with mains derived EHT.

Peter

[Helder Crespo]

Thanks Argus25 and Peter. I'm not sure whether I can find a proper permanent cap, such as the red Bulgin one mentioned by Argus25 (probably the same featured in his restoration pdf), but I will definitely improvise one while working on the set to minimise the risk of shocks.

I have another question, this time regarding the cabinet. In the cream DAC90A that I finished restoring last weekend, I used Mr. Sheen for the inside (no water nor water-based detergents) and for the exterior finishing I used the same method described by Panrock in his webpage devoted to the restoration of a TV22: Paste No. 5 followed by a thin coating of beeswax. I was really happy with the results with my cream DAC90A - see below - but I wonder whether the TV22 was really that shinny when it came out of the factory (perhaps they did, but it's hard to tell from the few period photos I've come across). In my opinion, the shine looks great on cream formaldehyde/urea cabinets (adds to the 1950s look and aesthetics) but I'm not so sure about the brown mottled bakelite of the TV22. I kind of like the slightly dull appearance of my set as it is right now, and would rather end up with a clean but slightly matte finish. I guess that if I skip the final beeswax coating, the surface of the bakelite will eventually oxidise and become duller in appearance, but I'm not sure whether the oxidation will not extend further into the material. Any suggestions?

[Argus25]

Originally Posted by peter_scott

It's easier to measure the EHT with the naked connector but I must admit that I got bitten on three occasions when working on my TV22 recently. I hasten add that I'm nothing like as cavalier when working with mains derived EHT.

Yes, to avoid issues like this one trick was to set up a mirror to see the screen, rather than looking at it from the front and reaching around the back of the set to make adjustments. There is always something back there that will give you a zap.

[Argus25]

Originally Posted by Helder Crespo

I'm not sure whether I can find a proper permanent cap, such as the red Bulgin one mentioned by Argus25 (probably the same featured in his restoration pdf)

There is a nice style of Bulgin cap shown in the photo. Typically these were used on the anode connections of 807 valves and 2X2 rectifiers. They were once ubiquitous in things like wartime UK made Radar indicators. Now they are getting harder to find, it would seem, but it would not surprise me at all if somebody on this forum had one in their junk box.


....just saw these on the electrojumble website part VH402, they are a Bulgin P92:

http://www.electrojumble.org/Valves_etc.htm

[Helder Crespo]

Originally Posted by Argus25

....just saw these on the electrojumble website part VH402, they are a Bulgin P92:

Thanks!

[Helder Crespo]

Quick and simple question: I'm not in the UK right now, but would like to order some silicone rubber wire online to replace the cracked red and green wires feeding the mains dropper when I next go to London. I didn't measure the external diameter of the original wires, but I believe that a 22AWG gauge should be a close match, or perhaps 20AWG? It would be great to have your advice on this. Thanks!

[Argus25]

The perfect wire to get is called harsh environment wire from RS Components. It looks & feels exactly like old fashioned rubber covered hookup wire, but the insulation does not retract or melt and is completely un-degraded by soldering in any way. It comes in black, blue, brown red & green. The part No. for the black is 359-677 for example. Once you use wire like this you will never go back to other kinds for vintage restorations, it is wonderful. I know of no superior wire. It comes in 25m rolls, but I promise you, you will use them up quickly, I have been through a few rolls already on 4 or more TV restorations.

If you scroll to page 8 of this article I recently used some of this wire to connect up an IEC connector in a vintage disk drive project, the photo there gives a good view of this type of lovely wire:

http://worldphaco.com/uploads/EXTERNAL_DUAL_5.pdf

[Helder Crespo]

Thanks for the all the interesting information on RS's harsh environment wire!

[Helder Crespo]

Originally Posted by Panrock

Hi Helder,

We meet again! Glad you've posted on this board and you're going to have a go yourself. You'll find here a useful store of experience and knowledge - and enthusiasm!

You'll probably also seen my own example of a TV22 restoration HERE. This also used 'replace all waxies and electrolytics' technique - though only one at a time!

There are different views held about doing this. In my case, it was the best option because the restoration was a commercial one. Time was of the essence and I wanted to achieve a set with as many as possible of the faults removed, as quickly as possible and with minimal effort.

However, if you are electrically competent, aware of the various safety hazards and yes, ideally have a variac, then you 'should' learn much more by gradually bringing the set to life as you fix each fault - one at a time. Although for the beginner, there may well be episodes of despair during the learning process! Some experienced folk may find doing things this way quicker and more efficient than doing a 'blanket replacement'. It's also time-efficient, because they often know the faults they'll find before they check and they can 'read' the raster (for example) for clues.

As regards the TV22 LOPT, I know there are those here who may consider my method of warming and pulling off the pitch excessively 'brutalist'. Again, in my case, this was simply much quicker than leaving it for days to dissolve in olive oil. As has been suggested elsewhere here, thoroughly drying out the windings by passing a current through them can be a good idea and improve the performance later. I invite opinions as to whether the direction of flow of the warming DC makes any difference as regards polarising the core...

Once in its cabinet, a TV22 can run rather warm when left on for a long period. On occasion, I have fitted a small fan into a circular hole cut into the top of the LOPT cover.

The rubber insulated multicore wiring from the RF/IF tray and the internal mains wiring can perish inside even when it looks OK outside. It's nice to keep the looms looking as original as possible externally when replacing their internals. In my case, working commercially, I always replaced all the mains wiring regardless of apparent condition.

Again, some would throw up their hands in horror when in this case I didn't seek out a new 'correct' mains connector but wired in a new mains lead directly, with strain-relief and a grommet. I drew comfort from my understanding that the original-style connectors today are only legal up to 50v.

So there you have it Helder. Enjoy getting to know your new TV22 - a recognised style icon that can work jolly well too. You'll find plenty of support available here.

Steve

Thanks Stephen!
Sorry for the late reply. I do pay close attention to originality, and even though I'm not a fan of capacitor restuffing for several reasons, I try to keep any visual changes due to necessary repairs to a minimum, down to finding similar-looking wire diameters and colours in case of any replacements. Even though I very recently restored a DAC90A, also to test my small improvised bench in London, I probably won't have the time nor the conditions to work on the TV22 myself (apart from minor things and the final polishing and waxing of the cabinet), this if I want to meet the goal of watching a film on it around Christmas time. I will hand the set to one of the curators of the Dulwich museum that has kindly agreed to help me with it, and in this situation anyone would prefer to work on a clean but untouched set than on a partial restoration.
Helder

[Argus25]

Originally Posted by Panrock

As regards the TV22 LOPT, I know there are those here who may consider my method of warming and pulling off the pitch excessively 'brutalist'. Again, in my case, this was simply much quicker than leaving it for days to dissolve in olive oil.

Steve

I don't know who suggested olive oil would be a "solvent" to dissolve pitch. I'm surprised it would dissolve it completely even after 6 months, unless it is some sort of industrial grade olive oil not for human consumption.

At the risk of repeating myself, the correct solvent for pitch is Mineral Turpentine, or the closest derivative to that. It takes about three days to one week for a TV 22 Lopty, because the hardened pitch is very thick & brittle, but as it progresses, the process speeds up. It pays to change the Turps bath one or two times over that period.

WD40 might be an alternative solvent, I have not tried it, but it is much more plausible than olive oil. But you would have to buy a few large cans of it.

[Panrock]

Thanks for the correction Hugo. I was working from memory, and this ain't what it used to be (come to think, it was never much!).

Something that emerges from these discussions... different people have their own 'pet' techniques. OT: One example is cabinet restoration. I was self-taught in this regard - never read up on the 'experts' - but nevertheless obtained pleasing results and had happy customers.

Steve

[beery]

Originally Posted by Helder Crespo

Even though I very recently restored a DAC90A, also to test my small improvised bench in London, I probably won't have the time nor the conditions to work on the TV22 myself (apart from minor things and the final polishing and waxing of the cabinet), this if I want to meet the goal of watching a film on it around Christmas time. I will hand the set to one of the curators of the Dulwich museum that has kindly agreed to help me with it, and in this situation anyone would prefer to work on a clean but untouched set than on a partial restoration.
Helder

Hi Helder,
your set will certainly be in good hands at the museum.
I do hope we have not put you off restoring old tellys in the future. I do think thst the TV22 is not a great set for a beginner. An easier place to start might be a late 50s set or even a 1960s set. A nice Thorn/BRC (Fersuson, HMV, Marconi) set with a jelly pot lopty is a great place to start. It is a lot harder to do any damage to these sets if you replace one capacitor at a time and then power up to see what fault that component has cured.

For me a BRC 981 was my first set when I was 14 (late 1960s 16" 405 lines only). My second set was an Invicta T102 from 1949 that was beyond my abilities at the time, with a TV22 being my third set. I learnt how to fix them all in the end though and I've now lost count of how many sets I have, its all good fun.

Cheers
Andy

[Helder Crespo]

Thanks Andy. My main limitations are indeed my inexperience, but also my very limited workspace and equipment in the UK. I definitely never felt put off by anyone here; on the contrary. I am very impressed with the technical and human qualities that I've encountered so far.
All the best
Helder

[Helder Crespo]

Hi. My set has been recapped, the lopty died after a few hours (short between primary and secondary windings), but has been rewound and fitted. I'm getting line timebase issues, as shown below. I will try to optimise C28 (on the 1091 trader sheet for the mk. 2 chassis) and hopefully will be able to try a new PL38 during the weekend. It would be great to have your opinion and suggestions on these and possibly other steps I should take. Resolution is affected too. For comparison I'm also posting an image from another TV22 (I found it online some time ago; not sure if it's from the forum) which shows excellent linearity and resolution.
Many thanks
Helder