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Vintage Television and Video Vintage television and video equipment, programmes, VCRs etc. |
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16th Oct 2019, 3:23 pm | #21 |
Hexode
Join Date: Sep 2019
Location: Crystal Palace, Bromley, London, UK.
Posts: 417
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Re: Bush TV22 Mk2 - first approach using a variac
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. |
23rd Oct 2019, 5:27 pm | #22 | |
Hexode
Join Date: Sep 2019
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Re: Bush TV22 Mk2 - first approach using a variac
Quote:
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. |
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23rd Oct 2019, 9:22 pm | #23 |
Dekatron
Join Date: Mar 2008
Location: Worthing, West Sussex, UK
Posts: 5,185
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Re: Bush TV22 Mk2 - first approach using a variac
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 |
24th Oct 2019, 4:16 am | #24 | |
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Location: Maroochydore, Queensland, Australia.
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Re: Bush TV22 Mk2 - first approach using a variac
Quote:
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. Last edited by Argus25; 24th Oct 2019 at 4:22 am. |
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24th Oct 2019, 6:20 am | #25 |
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Re: Bush TV22 Mk2 - first approach using a variac
......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. |
24th Oct 2019, 8:40 am | #26 |
Dekatron
Join Date: May 2003
Location: Edinburgh, UK.
Posts: 3,274
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Re: Bush TV22 Mk2 - first approach using a variac
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 |
24th Oct 2019, 9:58 am | #27 |
Hexode
Join Date: Sep 2019
Location: Crystal Palace, Bromley, London, UK.
Posts: 417
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Re: Bush TV22 Mk2 - first approach using a variac
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? |
24th Oct 2019, 2:21 pm | #28 |
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Re: Bush TV22 Mk2 - first approach using a variac
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.
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24th Oct 2019, 2:30 pm | #29 | |
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Re: Bush TV22 Mk2 - first approach using a variac
Quote:
....just saw these on the electrojumble website part VH402, they are a Bulgin P92: http://www.electrojumble.org/Valves_etc.htm Last edited by Argus25; 24th Oct 2019 at 2:52 pm. |
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24th Oct 2019, 3:58 pm | #30 |
Hexode
Join Date: Sep 2019
Location: Crystal Palace, Bromley, London, UK.
Posts: 417
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Re: Bush TV22 Mk2 - first approach using a variac
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24th Oct 2019, 5:30 pm | #31 |
Hexode
Join Date: Sep 2019
Location: Crystal Palace, Bromley, London, UK.
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Re: Bush TV22 Mk2 - first approach using a variac
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!
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24th Oct 2019, 10:35 pm | #32 |
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Re: Bush TV22 Mk2 - first approach using a variac
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 |
24th Oct 2019, 10:43 pm | #33 |
Hexode
Join Date: Sep 2019
Location: Crystal Palace, Bromley, London, UK.
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Re: Bush TV22 Mk2 - first approach using a variac
Thanks for the all the interesting information on RS's harsh environment wire!
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26th Oct 2019, 4:50 pm | #34 | |
Hexode
Join Date: Sep 2019
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Re: Bush TV22 Mk2 - first approach using a variac
Quote:
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 Last edited by Helder Crespo; 26th Oct 2019 at 4:51 pm. Reason: typo |
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27th Oct 2019, 1:08 pm | #35 | |
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Re: Bush TV22 Mk2 - first approach using a variac
Quote:
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. |
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27th Oct 2019, 1:41 pm | #36 |
Nonode
Join Date: Feb 2005
Location: Worcestershire, UK.
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Re: Bush TV22 Mk2 - first approach using a variac
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 |
27th Oct 2019, 5:01 pm | #37 | |
Heptode
Join Date: Jun 2006
Location: Ware, Hertfordshire, UK.
Posts: 988
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Re: Bush TV22 Mk2 - first approach using a variac
Quote:
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
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29th Oct 2019, 9:36 pm | #38 |
Hexode
Join Date: Sep 2019
Location: Crystal Palace, Bromley, London, UK.
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Re: Bush TV22 Mk2 - first approach using a variac
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 |
3rd Feb 2020, 9:53 pm | #39 |
Hexode
Join Date: Sep 2019
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Re: Bush TV22 Mk2 - first approach using a variac
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 |