Calling all Eidophor experts

[Malcolm G6ANZ]

We get our vacuum bits from Severn vacuum Service (http://www.severnvacuum.co.uk/)
they may be able to help. When i get home I'll post a photo of the filament we use Photobucket is a banned site where I work !
Malcolm

[Malcolm G6ANZ]

An afterthought. I recall an article in CQTV the magazine from the BATC about eidophors. I think it was around 1998/2000

[G8KBG Tony]

CQ-TV 168 - November 1994.

Free to download at the BATC site.

Regards,

Tony

[Malcolm G6ANZ]

Here is a photo of a filament/cathode I use on the linacs at work.
http://i131.photobucket.com/albums/p...psb1d73fab.jpg
The actual spiral is about 0.5 cm diameter and when running takes about 7.5A and shines as a bright emitter. The cup surrounding it is the launch/focussing electrode and ensures that the electrons come off the cathode at the correct angle and speed. This filament is a scrap one due to the number of pits in the tungston.

Malcolm

[Lucien Nunes]

Tony, thanks for the link, I couldn't download the file although the site says you don't need to be a member to do so. I will look again later.

Interesting pic Malcolm, unfortunately I won't be able to get a close look at the Eidophor equivalent for a few weeks, will post a pic when I do.

Lucien

[grindrod]

This is a fascinating thread!!! Please keep us updated with progress Lucien.

Have a good holiday! Martin

[dave walsh]

It is indeed very interesting, even if you didn't know what it was .

I'm still wondering if was I completely off the track with my naive question in post 6*? Today I came across this letter in PW February 1952-titled Progress [?]

"Not only are high pricesa disgrace to the battery set manufacturers but Television has done little better. Twenty years ago Baird showed us a picture full size on a theatre screen, yet today we are offered for home use a puny 10" or at best a 15inch picture. Now designers, why not a 2ft or 3ft projected picture on a flat wall screen". Sadly Mt Attwood of South London had no real hope of an answer I suspect. I can't find one anyhow.

It has a strange resonance with the thread on here about flat screens failing for the want of reliable capacitors although I realise it's not projection TV technology.

Dave W

[Lucien Nunes]

The system referred to in your earlier post is the projection CRT using an internal phosphor screen, of which I think the main details are fairly reliably documented as it was the starting point of Cintel. As such it was unrelated to Eidophor although projection CRT technology held its own until quite recently. There's some info compiled by Douglas Brown and Malcolm Baird here. AFAIK the Eidophor was not demonstrated until 1943.

It's interesting to note that Baird's glassworker Johnson had trouble with insufficiently annealed Hewittic bulbs that were being used for CRTs. I have also had trouble with seal cracks in Hewittic bulbs, in their more customary application in Hewittic mercury-arc rectifiers. Although well respected rectifiers in their day, I have had more Hewittic glassware fail than any other make. Not a problem with the Eidophor, where the flask is metallic except for the window.

Lucien

[dave walsh]

Thanks Lucien, I will try to follow up the info you have referred me to but like Mr Attwood, I'm still wondering if the Baird inferior CRT process could have been applied in any domestic sense and rather quicker. One interpretation of TV development, as with so many other professions, seems to depend on the human element as much as the technology [VHS v BETA] eg what would have happened if Baird and Reith had not been at the same school with the subsequent apparent life long animosity. That's why I was interested in this more specific thread.

Notwithstanding the technical differences you illustrate, it is overall, still very difficult to get people to believe that widescreen colour TV was available in the 1930's. I couldn't believe this at all myself in 1970 when I met [by chance] a Canadian Department Store owner [just off Piccadilly in Manchester] who told me he'd had such a receiver [by which he meant a colour set-I don't know what it was] mounted on the wall in his luxury apartment overlooking Hyde Park circa 1935! UK Colour TV was only a couple of years old then of course. Based on my limited but apparently superior technicaI knowledge, I just thought he was making a ridiculous boast but actually, he might have been trying to point something out to me. He'd noticed the 16mm camera I'd just had repaired and this got him talking to us [he seemed a bit lonely], I'd decided that he was an imposter and making it all up, until he showed my young wife and myself over the whole store, including the workshops. I've always regretted not taking him more seriously and getting further details. Why did he want to tell us all this?
Dave W

[Steve_McVoy]

Here is one of Baird's theatre projection tubes from the late 30s:

http://www.earlytelevision.org/rauland_crt.html

[peterpixel]

I have only just seen this thread so apologies for the late response.I operated the Eidophor at Salford University from 1970 to 1979 and it was situated in the Chapman building in lecture theatre 1. I think it was sold off in the 80s or 90s as there was nobody left to operate it.Contrary to an earlier statement that no special training was necessary to use it this is not true.The training course for operators was less than a week but as the heater current and grid bias had to be set each time it was used and the beam current knee found anyone untrained could quite easily blow the cathode heater.The Salford machine was the result of a swap for an ex Granada EMI telecine with the University of Sussex.George Gilbert was mentioned and I believe he used to operate the one at the Odeon.George gave me a lot of work installing Eidophors in the Northwest and on one occasion in Sweden.Before it can be moved the lamp has to be dealt with as already said and the electronics rack removed to lessen the weight.I have located some cathodes and I still have the service manual.I will be in touch with you Lucien and hope your mission is successful.Peter Wilson.

[Stuart R]

Don't worry about the late arrival of your post, Peter. It's great that you've got in touch!

I'm amazed how a bit of search engine dabbling and a great forum such as this bring can bring together obscure parts and information that have been squirreled-away around the country -narrowly escaping the WEEE skips.

Looking forward to seeing how Lucien gets on with this and his museum project. I know it's keeping him and his volunteers very busy.

Regards,

SR

[Lucien Nunes]

This is brilliant news! Thanks for getting in touch Peter, I had not spotted your post either until now. So far we have not investigated the innards of the machine at all, pending finding suitably expert advice. It's in the museum store at the moment, where we can admire it but not effectively work on it yet. The plan had been to hold an open day at Electrokinetica this year, however unexpected circumstances for a couple of us have made for rather slow progress and realistically it is going to be next summer. Later on this year it should be possible to set up the various projectors as their space is going to be cleared of storage in the next logistics weekend, so we will be have elbow room to work on the Eidophor in a few months time.

I look forward to learning more about its care and management, we don't have any documentation at all so this is going to be most essential. Valve electronics we can cope with, we have a high vacuum expert or two, but I am sure that having experience and inside knowledge such as yours on the team will be the deciding factor in its restoration.

Thanks again
Lucien