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Old 29th Jun 2016, 8:45 am   #101
BassoonBloke
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Default Re: HMV 905 Project

Hi Andy,

Well that's just brilliant !!
The fact that the first thing you do when you get a decent scanned picture is watch a film is just great
I've been watching progress with great interest and am very impressed. I know that a bit more twiddling and it'll be up to full working spec.
It's just waiting to show an early Hartnell Dr Who though
Well done, excellent.

Alan.
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Old 29th Jun 2016, 9:13 am   #102
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Default Re: HMV 905 Project

I would never have the technical competence to repair a vintage TV, particularly one so very vintage, but I do have a mental vision of doing that and then watching old Dr Who episodes on it!
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Old 29th Jun 2016, 11:14 am   #103
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Default Re: HMV 905 Project

Brilliant work! Fabulous progress!

I love it.

Peter
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Old 29th Jun 2016, 2:20 pm   #104
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Default Re: HMV 905 Project

You have my admiration for the dedicated attention you give this fine set.
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Old 29th Jun 2016, 4:33 pm   #105
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Default Re: HMV 905 Project

Yes exceptional work! I have followed your progress with great interest. the difference between the before and after pictures is incredible !

Rich.
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Old 29th Jun 2016, 4:44 pm   #106
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Default Re: HMV 905 Project

I have to say that this really is exceptional work.

At the start of this thread I have to admit that I thought that there was far too much work and too many parts missing for this restoration to ever succeed. It's to your great credit and skill that this TV has actually displayed a picture, as I really did think that it would either take many years or eventually be given up as a lost cause.

Very, very well done - I wouldn't have dared start it in the first place.
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Old 29th Jun 2016, 7:30 pm   #107
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Default Re: HMV 905 Project

I too have been following this thread with great interest.
Well done andy , that's another one saved.

Robin
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Old 29th Jun 2016, 8:22 pm   #108
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Default Re: HMV 905 Project

Quote:
Originally Posted by Leon Crampin View Post
For dealing with light chassis rust, I would suggest light mineral oil rubbed in with a green "Scotchbrite" scouring pad (best binned afterwards).
My rust treatment method is very similar. I scrub the area with a brass suede brush to remove the loose surface rust then I rub in some general purpose oil such as 3 in 1. The area loses its rusty colour and it is also rust proofed for future protection. I have also had success using automotive rust converter/treatment after the wire brush treatment.
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Old 29th Jun 2016, 8:29 pm   #109
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Is that Edward Judd in picture 4 ?
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Old 29th Jun 2016, 11:48 pm   #110
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Default Re: HMV 905 Project

Correct!
Any idea as to the film?

I can give a clue if if needed...

cheers
Andy
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Old 30th Jun 2016, 4:53 pm   #111
brianc
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Default Re: HMV 905 Project

As Jac says - most impressive! You put me to shame with your progress as I have very little to show on my very rusty 707 chassis. Maybe a bit later when I fell better.
On the rusty note has anyone got a scrap 706/707/904/905 chassis for sale (hen's teeth come to mind)? Any condition will do as I will strip it and have the bare chassis re-finished. In that way, I can remove bits from the original and mount them on the new chassis - this would make things much easier - I would even return the spare bits and rusty chassis
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Old 30th Jun 2016, 5:54 pm   #112
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Default Re: HMV 905 Project

The intermediate frequencies are very low being only 4.5Mc/s sound and 8Mc/s vision. This means that the local oscillator frequency is 37Mc/s.
Andy has informed me that the spot alignment frequencies are 7.3, 8.0 and 8.7Mc/s, this tells us that the vision IFs are aligned for a symmetrical response about the carrier frequency. The tuned circuits are heavily damped but nevertheless it's unlikely the maximum vision response is >2Mc/s. With such a small CRT this will be acceptable.

DFWB.
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Old 30th Jun 2016, 8:53 pm   #113
Thyristor
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I would say the film is either:
Guess 1 'The Day the Earth Caught Fire'
Guess 2 'Invasion'
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Old 1st Jul 2016, 10:05 pm   #114
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Default Re: HMV 905 Project

Yes Thyristor, it is 'The Day the Earth Caught Fire'.
Edward Judd was great, but he was out-acted by Leo McKern. It is one of my favourite films. Btw, years ago I recorded it on to VHS from BBC2 (remember the Saturday Matinee) and it was all in black and white. However now I have the DVD I realize that the start and end of the film were originally coloured orange to indicate heat, so I guess the BBC simply transfered it black and white. Who needs colour anyway!

Back to the 905.
Thanks for all those that have congratulated me thus far. I have benifited by the assitance of many people on this project. I will give full credits when the set is complete.
It might have seemed impossible to get to this point, but I figured it was worth a punt since a much more expensive complete set could well have had a duff EHT transformer, lopty and CRT, so at least in this case I knew what I had (or didn't have) to start with.
I still have to make the scan coils though. I also need the correct HMV speaker grill and the safety glass. Oh yes, I also need to make the CRT bulge for the cabinet back...

I've spent just a short time looking at waveforms in the IF stages.
It all looks fine, but scoping the output of the video amp reveals that the video waveform looks fine at a low level, but as the contrast control is turned up, the syncs get larger whilst the picture content gets crushed. I'm not sure why.
I also can't find the resonant point of the sound trap just yet, it must be somewhere...

Cheers
Andy Beer
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Old 2nd Jul 2016, 11:03 am   #115
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Default Re: HMV 905 Project

Quote:
I've spent just a short time looking at waveforms in the IF stages. It all looks fine, but scoping the output of the video amp reveals that the video waveform looks fine at a low level, but as the contrast control is turned up, the syncs get larger whilst the picture content gets crushed. I'm not sure why.
A truly amazing restoration - I have really enjoyed reading about it.
As to the crushing, could it be that one of the later video stages has low gain and, as the contrast is turned up to compensate, an earlier video stage becomes overloaded?

Barry
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Old 2nd Jul 2016, 11:36 am   #116
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Default Re: HMV 905 Project

Andy,

I must echo all the congratulations...it's an amazing restoration tour de force!
I would say your patience and persistance are quite exceptional!!

Trevor.
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Old 2nd Jul 2016, 6:29 pm   #117
beery
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Default Re: HMV 905 Project

Hi all,
after a little investigation I found that I had connected C44 to the cathode of V8 instead of the screen grid. Moving it over improved the gain and enabled the sound rejector to function. There is a lot more contrast and no sound on vision.

I've included a picture Janet Munro.

I now need to de-rust the focus assembly a bit in order to be able to centre the picture.

More later...

Cheers
Andy
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Old 2nd Jul 2016, 9:11 pm   #118
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Default Re: HMV 905 Project

Hello Andy,
This has totally blown me away. Incredible work and dedication. Well done!
Amazed! John.
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Old 3rd Jul 2016, 3:36 pm   #119
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Default Re: HMV 905 Project

Yes absolutely fascinating Andy. All the skills you and others exemplify are really under-appreciated these days. Maybe the current retro craze [crazy as it is] might shift the balance a little. When craft/tech based programs are made for TV they are never trailed or tried in near a peak viewing spot-perhaps for obvious reasons but who knows what interest could be created? James May and his disassembling Workshops got a "hammering" but 9pm on BBC4 wasn't giving things a chance really Regardless of TV it would be a good idea to film one of these sort of restorations in more or less full length [subject to reasonable editing of course] if only for posterity! They do it with cars on Quest. Maybe BVWS could consider it?

Your "Day The Earth Caught Fire" viewing choice is appropriate in today's "climate" so the spherical CRT image [p 117] must be an example of "Global Warming"

Dave W
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Old 28th Aug 2016, 12:03 pm   #120
beery
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Default Re: HMV 905 Project

Hi all,

After a holiday, I'm now back on the HMV 905.

I've just made some of the tube mounting metalwork.

The first photo shows the tube mounting gantry being folded using a vice mounted bending tool.
The second photo shows the completed parts after spraying with satin black Hammerite.

I also rubbed down the rusty forcus coil assembly (not pictured) and painted that with Hammerite as well. I did not want to use rust converter on it as the assembly can't come apart and I had to protect the 6K ohm winding...

Cheers
Andy
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