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Old 14th May 2016, 11:32 pm   #1
draenog
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Default HMV 907 pre-war television

Hi,

Last year a HMV 907 was sold at the BVWS Royal Wootton Bassett auction. For various reasons I wasn't able to bid on it at that time, so I was pleased to get a second chance when it appeared in the next Airwaves issue (from Steve Harris). Since getting it in September, I've been slowly restoring it. I'd hoped to get it done by NVCF, but the laborious re-stuffing of the capacitors took longer than expected - it's very hard to keep motivated!

I'll do a proper write-up later - this is just a quick post before the NVCF. At the moment, all capacitors have been re-stuffed, several modifications/divergences from the circuit diagram have been undone, and a couple of resistors have been replaced (from opportunistic testing of those removed during the capacitor restuffing). I've attached a couple of pictures showing the current state. As can be seen, the CRT is very good, producing a nice bright picture. The major problem at the moment is lack of width. Adjusting the width control beyond this point leads to stretching of the left edge. However, I'm pretty pleased with the results so far.
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Old 15th May 2016, 8:08 pm   #2
stevehertz
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Default Re: HMV 907 pre-war television

Lovely job, well done. Would that be Patrick Troughton as Dr Who?
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Old 15th May 2016, 11:20 pm   #3
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Default Re: HMV 907 pre-war television

I`m amazed how good that crt is.
I`m looking forward to the full write up.

Robin
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Old 17th May 2016, 3:24 am   #4
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Default Re: HMV 907 pre-war television

Quote:
Originally Posted by stevehertz View Post
Lovely job, well done. Would that be Patrick Troughton as Dr Who?
Yes, it's Patrick Troughton in "The Mind Robber" (second story, season 6, 1968). Quite a good story, although "my Doctor" was Tom Baker (I can just remember the later Jon Pertwee episodes, e.g. The Sea Devils).

Quote:
Originally Posted by line sync View Post
I`m amazed how good that crt is.
I`m looking forward to the full write up.
Yes, I'm really pleased with the CRT, especially compared with the dim CRM92's my brother's been testing recently (I've also just picked up a Murphy V114 at the NVCF and I don't expect that CRM92 to be any better). It's even more amazing as it's only got an anode voltage of 3500 (mains derived of course)!

I've been a bit distracted by the V114 (first problem was getting it out of the case as the mask was firmly welded to the safety glass). Hopefully I'll get the width sorted over the weekend and I'll start a write-up then...
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Old 17th May 2016, 6:14 am   #5
Neil Purling
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Default Re: HMV 907 pre-war television

What is the visible width of the picture? The CRT looks very small in that console case. There's a radio as well I assume.
I am just wondering how close to that bug-eyed monster you would have to be in order to watch comfortably.
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Old 17th May 2016, 7:50 am   #6
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Default Re: HMV 907 pre-war television

The 9" picture [approx 7" X 9"] is surprisingly watchable even in a fair sized room. The 907 at the Dulwich museum is in the huge front room but the entertainment value is still excellent.
It may seem very small after watching an oversize flat screen but the brain adjusts after a short while and it becomes just another telly. A 14" screen gives a very good account of itself in a British living room.
Odd that today we sit 6ft away from a 60" screen but the cheap seats in the cinema were always in the front row. Just my own views. John
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Old 17th May 2016, 10:13 am   #7
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Default Re: HMV 907 pre-war television

Excellent restoration-congratulations Are there any theories as to why some sets seem to turn up with a relatively good CRT and others can be a bit dim Is it the obvious ie the amount of use originally or production/type variations. I remember our set getting fainter and fainter with curtains having to be drawn [especially in the summer] when I was a child and the frustration this created!.

The question of screen size is an interesting psychological issue John. I can't cope with the cinema front row but then domestic screens aren't 20' high [yet].
I chose to have a small but sophisticated and really expensive 14" JVC colour set in the 80's [when the standard was 21"] putting TV in "it's place" I thought. My first "massive" [in every way] LG 32" set made a very big impact but every time we've used a bigger screen since then the effect has rapidly diminished. It's a very large lounge here in Bexhill but even so, when we unpacked a bargain 50" FS we thought we'd made a mistake. As you said John we see with our brain which processes and adjusts.i

Now, viewed from 8 to 12' away, the "big screen" is just taken for granted unless something visually spectacular is on -when it comes into it's own! In my workspace here I have 14" portables to the left and right 3 or 4 feet away and don't feel deprived. As long as I can watch it I don't have any real concerns. Some people do-others seem to be unable to watch anything in B+W which means they are really missing out in terms of a top class 405 line picture or it has to be a 4x3 image even in 625 colour. Will we accept screens taking up the whole wall in the future as Sci Fi films often suggest?

Another strange phenomena is an apparent narowness of interest among enthusiasts. The number of times I see the same period material eg Dr Who/The Copronation etc being shown at the excellent live TV exhibitions or on here, is surprising considering what's available. Some of the classic Attenborough stuff is now found to be in colour [BBC4 tonight]. Where does that leave some of us I wonder

Dave


Tom Baker? Forshame draenog! It was downhill all the way after Hartnell and Troughton until the Cardiff revival-now [sadly] formulaic again!

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Old 17th May 2016, 11:31 am   #8
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Default Re: HMV 907 pre-war television

Well done with the restoration work. You have an exceptionally good tube there.

When I had my own 907 many years ago, it was fitted with a 'replacement' Emiscope 3/3 I obtained from Gerry Wells. The picture was bright but unlike yours had a noticeable ion burn. This is the set in the attached illustration.

Such tubes today seem unobtainable. When I restored a 907 a few years ago for a customer, I had to adapt it to take an even earlier Emiscope 6/5. See HERE for the full story.

Steve
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Old 17th May 2016, 1:56 pm   #9
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Default Re: HMV 907 pre-war television

That's great work.
I love the woodwork on these sets.

Yes, re-stuffing takes forever, but it is worth it. In fact I think that having to wait so long before you can even switch a set on for the first time makes it all the more rewarding in the end.

The tube is fantastic. I had an 1804 once, with its original pre-war style 10" CRT. It had hardly been used and I was amazed at the pictures from such low EHT.

Regarding bright and dim tubes, well assuming that the tubes you are comparing still have a hard vacuum, it is surey mostly down to how much usage they have. The old EMI tubes seem to always develop ion burn eventually, so that this set has no burn suggests it has hardly been used and also of course has a very good vacuum.

I think that pre-war sets have had interesting lives to survive until today. Most were overhauled afer the war and worked into the early 50's, being abandoned when larger screens became readilly available. Others ended up on the second hand market and were kept going into the 60s I guess (maybe as hobbyists' sets) and that would explain the differences. Keeping pre-war sets going for so long did not make a great deal of sense, but then neither did keeping large non-working sets in the house, but we are so glad people did.

I'm looking forward to the full write up.

Cheers
Andy
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Old 7th May 2019, 3:46 am   #10
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Default HMV 907 and Spiderman

Back in 2016 I provided a work-in-progress update on the restoration of my HMV 907:

https://www.vintage-radio.net/forum/...d.php?t=126454

I completed the restoration but I've never had time to do a proper write up. I promise to try and do one in the coming weeks. In the meantime, here's a video I made last September of the HMV 907 connected up to a PS4:

https://www.youtube.com/watch?v=-7wJSfv0lS4

Please don't form a vigilante mob and kill me! I work for Sony developing the toolchain for the PS4. We had a series of lightening talks, where you could do a 10 minute talk on anything. I chose to do one on pre-war televisions, and I brought in a couple of props, and showed the video. In order to get the audience interest (all IT geeks) I had to show something they could relate to. For the record I don't own a PS4 and had to borrow one from work.

My plan worked, and I won the prize for the best talk (a £50 amazon voucher)
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Old 7th May 2019, 3:51 am   #11
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Default Re: HMV 907 and Spiderman

BTW, the contrast and brightness is turned up higher than normal to get a decent picture in the game...
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Old 7th May 2019, 6:40 am   #12
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Default Re: HMV 907 and Spiderman

Quote:
Originally Posted by draenog View Post
In the meantime, here's a video I made last September of the HMV 907 connected up to a PS4:

https://www.youtube.com/watch?v=-7wJSfv0lS4
42,973 views! I thought I was doing well with ~ 5,500 views for a video of the HMV 904 gained from over 4 years since posting in 2015

It's clear what gets the clicks. What next "Love Island" in 405-line Black and White? Phwoar, look at the low definition, the less you can see the better

And No I have never watched Love Island.

Last edited by Catkins; 7th May 2019 at 6:45 am. Reason: clarifying a point
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