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Vintage Television and Video Vintage television and video equipment, programmes, VCRs etc. |
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21st Sep 2020, 4:47 pm | #1 |
Octode
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Question on EF91/EF80 and old TV's
This is a how long is a piece of string question and I am sorry for that, but!
I am planning a bit ahead and looking to see what starter TV I could be looking for in the style of 405 Line B&W wooden cabinet. Preferably not a tall cabinet with the speaker in the bottom half. And definitely not anything one would consider rare, I do not do rare. I will leave them to others if I end up scrapping a set I would not like a bunch of angry collectors after me! I would have liked to go for one with EF91 valves, but this is only because I have been using them in an audio amp, but, from a Ebay auction I also have pulls of EF80's, 184 etc I would also have liked something with a mains transformer as I do not like droppers and live chassis, I have a RS 200VA isolation transformer available at this end, but suspect I would really need bigger unless I keep it to a small set. Listing the watts or VA does not seem to be a requirement of the 50's. And circuits all seem to show live chassis TV's I tend to think many of the ones that are going to be mostly available will be EF80. So down to the questions what models would you TV experts recommend for a starter in this area. I have a modulator on the way from the states, a Sony 9-90UB to use as a test TV. B8ut before I go down the journey I thought it best to ask opinions. Sorry if in the wrong section, not asking to buy anything yet so thought this would be suitable, please move if not. Adrian |
21st Sep 2020, 4:55 pm | #2 |
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Re: Question on EF91/EF80 and old TV's
Both EF80s and EF91s are very plentiful, both as NOS and pulls. 1950s tellies were full of the things and every TV workshop had lots of spares. They were mostly used in 300mA series string heater arrangements, but will be just as happy fed from a 6.3V transformer.
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21st Sep 2020, 5:18 pm | #3 |
Dekatron
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Re: Question on EF91/EF80 and old TV's
Not many British woodies had mains transformers, KB comes to mind though.
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21st Sep 2020, 6:08 pm | #4 |
Octode
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Re: Question on EF91/EF80 and old TV's
Hello Bill, guessing the ITT-KB list in the BVWS cdrom is the list to look at, not found any transformer one yet on a quick glance so would think there are very early and probably a bit rare.
If I can use an isolation transformer I will be happier. Adrian |
21st Sep 2020, 7:25 pm | #5 |
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Re: Question on EF91/EF80 and old TV's
Hi Adrian, when you get one feel free to PM me and I'll look you out a set of tested pulls (excluding CRT) for whatever it is
Cheers, Ed |
21st Sep 2020, 7:50 pm | #6 |
Octode
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Re: Question on EF91/EF80 and old TV's
Thanks Ed;
There is a Ferguson 991T on at the moment, that is probably within a few hours of me, other then that all are some distance away, we shall see what transpires, there should be no rush apart from my own impatience. Adrian |
21st Sep 2020, 8:03 pm | #7 |
Hexode
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Re: Question on EF91/EF80 and old TV's
I always liked the Thorn 900 and 950 chassis, these used an autotransformer and ran quite cool without the dropper. My first TV as a teenager was a Marconiphone dual standard with the 900 chassis. I can't remember the valve lineup but I think the only difficult one to source was a PFL200 used as sync separator and video output.
Dave GW7ONS |
21st Sep 2020, 9:24 pm | #8 |
Dekatron
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Re: Question on EF91/EF80 and old TV's
Hi Adrian, what broad category of set are you thinking about getting?
1) A post-war BBC only set 2) A Band 1/3 set with a tuner 3) A dual standard 405/625 set As you are considering a TRF 991T I think you are in the 1) camp. Those are the sets I like, and an old Cossor 916 found me as I passed an antique shop window in Stockport. It has a round tube with a Double D profile mask, glassware that no doubt had its origin in wartime radar, wasn't it you that asked about PPI scopes a while back? Don't let the valve line-up unduly influence your choice, it's the power valves that are more likely to need replacing rather than the signal valves.
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21st Sep 2020, 10:10 pm | #9 |
Octode
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Re: Question on EF91/EF80 and old TV's
Hello Graham;
I guess a 1) or 2) would do me, if it keeps it simple. The modulator I have ordered is this one https://www.earlytelevision.org/405_modulator.html from the web site:- it will tune band I (45 mHz video, 41.5 mHz audio to 62.25 mHz video, 58.75 mHz audio or any frequency in between). I was just in the garage pulling out the transformer I thought was an isolating one, old RS stock number 208-529, looks like the secondaries are 55-0-55, two off but not isolated from each other and the primary has melted the insulation tape on it so I would not trust it anyway. Think it will be heading for the bin. I like things to be earthed in the house, I need to have a look at what other transformers I have, and perhaps a rethink. Adrian |
21st Sep 2020, 10:11 pm | #10 |
Octode
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Re: Question on EF91/EF80 and old TV's
Question to add, do you all use isolation transformers or as it is?
Adrian |
21st Sep 2020, 10:19 pm | #11 |
Dekatron
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Re: Question on EF91/EF80 and old TV's
I don't use isolating transformers - but then I was a TV engineer for 50 years.
Peter |
21st Sep 2020, 10:37 pm | #12 |
Dekatron
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Re: Question on EF91/EF80 and old TV's
Be aware that most sets have a live chassis design, always check the chassis is connected to neutral!
I do prefer the single channel sets, although I do have several later 13 channel sets, all good clean fun! Mark |
21st Sep 2020, 10:44 pm | #13 |
Octode
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Re: Question on EF91/EF80 and old TV's
Found that the Vidor CN390/391 chassis uses a transformer, its a bookcase console set so probably bigger than I would like, but it would do at a pinch, not found any though.
Adrian |
22nd Sep 2020, 9:25 am | #14 |
Octode
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Re: Question on EF91/EF80 and old TV's
Went through a few of the service sheets for Ferguson, Cossor and ITT-KB last night seeing how many were transformer based, not found any Ferguson's to be transformer based, two Cossor sheets 996 and 1065 and a few ITT-KB 1015, 1191 & 1312, but all these, and the Vidor mentioned before still rectified the mains to provide HT.
So my original ideas will have to be modified I think, and a bit more study time is needed before I venture into this side of the hobby. Adrian |
22nd Sep 2020, 10:20 am | #15 |
Heptode
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Re: Question on EF91/EF80 and old TV's
The modulator in Post 9 requires a 405 line video input; hopefully you know this already and have one but I thought it worth a mention just in case.
Most enthusiasts use a standards converter and modulator all in one package such as the Aurora or Hedghog. |
22nd Sep 2020, 10:20 am | #16 |
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Re: Question on EF91/EF80 and old TV's
The philips 663a I think it was used mains transformers for both HT and EHT, I think it was only a 9" set but it weighed a ton!
Peter |
22nd Sep 2020, 10:49 am | #17 | ||
Octode
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Re: Question on EF91/EF80 and old TV's
Quote:
How successful I will be I am not sure, but thought it worth a try. Quote:
Adrian |
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22nd Sep 2020, 12:39 pm | #18 | |
Pentode
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Re: Question on EF91/EF80 and old TV's
The first (and only) set I restored was a Ferguson 988T. Nice little set, works well, not too challenging to restore. There seem to be a lot of comparable early ‘50s sets around with relatively straightforward chassis, available quite affordably. Even if you get something monumentally wrong or find yourself out of your depth, there’s bound to be someone keen to take the set on instead, and you won’t be short of guidance here anyway.
The old Ferguson is a mains-rectified HT set, most of them that age were. It’s not all that alarming if you’re sensible- make sure the mains lead is wired correctly, and if you’re nervous, keep a neon screwdriver handy just to check the chassis isn’t live. If you have an isolation transformer in any case, you should be fine. Common sense takes you a long way. Quote:
A bit like the old trick of hanging a tripler off the o/p valve, although done with more valves. Presumably much more expensive than a simple overwind. So fairly suitable for the OP, except perhaps on the count of value and scarcity.. Oliver Last edited by Oliver35; 22nd Sep 2020 at 12:48 pm. |
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22nd Sep 2020, 1:20 pm | #19 | |
Octode
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Re: Question on EF91/EF80 and old TV's
Quote:
I am also determined not to spend lots of cash on this, as I think the spouse is starting to get a bit put out with what I have and the space it takes. So cheap and smallish for the time being is my mantra. Amateur radio gear, valve radios, valve amplifiers, test gear, Satellite TV transmitter, computers etc. I am sure I am not the only one! Adrian |
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22nd Sep 2020, 1:36 pm | #20 |
Heptode
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Re: Question on EF91/EF80 and old TV's
Hi Adrian,
You might need to change you requirements a bit. So a bit of history... Early sets used isolating mains transformers that also provided mains derived EHT. They were big and heavy. In the late 1940s alternative methods of EHT generation were used. So manufacturers then looked at how to get rid of the heavy mains transformer. Most did away with it entirely by using mains droppers, but some manufacturers such as KB and Ekco used smaller auto transformers, which run cool, but do not provide isolation. Regarding isolation transformers, I sometimes use them when fault finding sets, but don't use them for running sets that are back in their cabinets. I do use them a lot at work where I develop mains powered lighting controls. Choices... Well Vidor did make a table set with a transformer, but it is very rare and has mains EHT. The Pye B16T is more common, but still hard to find and mains EHT. If you are not experienced in fixing vintage electronics you should steer clear of mains EHT which is far more deadly than a live chassis. Sets with auto transformers such as the Ekco TSC46 do not provide mains isolation, but don't use a mains dropper. The Pye B18T and LV20 do use a mains dropper, but it doesn't get very hot and is not located near the cardboard back if fire risk is your worry. Most 50s and 60s valve sets use mains droppers. The Pye PTV and Ekco TMB272 do have mains isolation transformers. The Thorn 900 dual standard chassis uses an auto transformer, so no mains isolation, but it runs nice and cool though. The Ferguson personal 11 is one such set. So you can either use a mains dropper or auto transformer set together with an isolation transformer. Or you can choose something like the Ekco TMB272. An isolation transformer to run a vintage transformer should be at least 500VA (think of it as 500W for now), as they are often derated for continuous running. I hope that helps a bit. Cheers Andy
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