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HMV 2635 BRC 950 MkII

 
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HMV 2635 BRC 950 MkII

Post by Colourstar » Sun Nov 08, 2015 12:14 pm

In anticipation of the arrival of the loft-find Ultra Bermuda 950 series set, I thought I'd dig out my other 950- an HMV 2635. This is a late one- probably 1967- as the cabinet and controls could easily lead you to think a 1400 chassis was fitted, but it ain't! I wouldn't be surprised to learn that this cabinet was carried over for use with the 1400. Of course HMV was merely a badge by this time. I can't imagine people accustomed to the grandiose veneers and craftsmanship previously associated with the products of His Master's Voice would have been overly impressed by the groovy 60s plastics and laminated plywood on offer here!

There's a label on the rear cover showing that it was sold as a second-hand model in September 1982 with a 3 month guarantee by BDTS of Cross Hills, North Bridge, Halifax. A reminder that even as late as that 1960s sets still had some life left in them. I'm surprised this one wasn't hard wired to 625-only operation.

Performance on 625 is very good indeed; the off-screen shots don't really do it justice. 405 isn't so hot however, with a rather smeary image, which is rather disappointing given the excellent performance these sets are capable of. The sound quality is surprisingly good; there's a fairly generously sized loudspeaker behind that small grille.

Steve
Attachments
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1972 Z-Cars
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Smeary 405 picture...
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405 close-up

 
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Re: HMV 2635 BRC 950 MkII

Post by nuvistor » Sun Nov 08, 2015 4:25 pm

Looks like some ringing or overshoot in the video on 405, whether RF/IF or video stage I am not sure. With a good 405 crosshatch or spot signal you should be able to see it on a scope. Probably too much info with a test card to see clearly on scope.

Frank

 
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Re: HMV 2635 BRC 950 MkII

Post by marc » Sun Nov 08, 2015 4:41 pm

Hi Steve,

That does look a smashing set and very nice to see it awake too :aad
I'm sure you'll have it sorted in no time :qq1

Marc.

 
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Re: HMV 2635 BRC 950 MkII

Post by Terrykc » Sun Nov 08, 2015 7:54 pm

nuvistor wrote:Probably too much info with a test card to see clearly on scope.
Not necessarily - the overshoot might show up well on the edges of the line sync, especially as it looks like a nice clean signal.

 
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Re: HMV 2635 BRC 950 MkII

Post by Cathovisor » Sun Nov 08, 2015 8:11 pm

Terrykc wrote:
nuvistor wrote:Probably too much info with a test card to see clearly on scope.
Not necessarily - the overshoot might show up well on the edges of the line sync, especially as it looks like a nice clean signal.

...and you'd certainly see it (if it's there) on a 'scope with a delayed timebase.

 
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Re: HMV 2635 BRC 950 MkII

Post by ntscuser » Mon Nov 09, 2015 5:13 am

Colourstar wrote:There's a label on the rear cover showing that it was sold as a second-hand model in September 1982 with a 3 month guarantee by BDTS of Cross Hills, North Bridge, Halifax. A reminder that even as late as that 1960s sets still had some life left in them. I'm surprised this one wasn't hard wired to 625-only operation.


I'm not surprised as retuning between three UHF channels was a bit of a chore compared to using the VHF dial plus its one UHF setting. That left the UHF dial free for fine-tuning of BBC2. Of course these days you can just leave it parked on the one setting.

What does surprise me is the recessed tube as that makes the cabinet much deeper than it need be. Also as you mention the plastic tube surround does look a bit cheap, on any set not just this one.

Your off-screen pictures remind me that even though it had only mean-level AGC the picture is still a lot more natural-looking to me than the sync-tip agc sets which came later.

 
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Re: HMV 2635 BRC 950 MkII

Post by Colourstar » Mon Nov 09, 2015 11:27 am

Good point re the tuning arrangements. UHF tuners can be touchy things at the best of times!

I suppose the set must be a little deeper than needs be with the recessed tube. It's not very HMV-like at all and does look a tad cheap.

The 950 is a well thought-out chassis in many respects and of course does away with the mains dropper and all it's inherent problems so runs fairly cool. Out of interest what's the different between the Mk1 and Mk2 versions of the 950 chassis, by the way?

Meanwhile here's a nice picture of Cilla Black as she was in 1971.

Steve
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Re: HMV 2635 BRC 950 MkII

Post by malcscott » Mon Nov 09, 2015 1:35 pm

The Mk2 had a flywheel sync pcb fitted.

 
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Re: HMV 2635 BRC 950 MkII

Post by Focus Diode » Tue Nov 10, 2015 8:21 am

This is the same set I worked on a couple of years ago and documented on this site. Before Steve got the set there was lots of previous repair work carried out. Seeing the set was sold as late as 1982 I wonder if it was aligned for peak performance on 625? Unfortunately due to urgently needed space I didn't have time to investigate further so returned the set to Steve.
Like the 960 portable the UHF tuner is dodgy. Without a spare to hand I find it best to select a high UHF channel. It's fortunate we've reverted back to the single UHF channel as it was when the set was new.

When you get the Ultra it would be interesting to compare the performance of both sets seeing the Ultra has the original 950 chassis where this HMV employs the 950 MkII chassis.
Cheers
Brian

 
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Re: HMV 2635 BRC 950 MkII

Post by Focus Diode » Tue Nov 10, 2015 8:27 am

malcscott wrote:The Mk2 had a flywheel sync pcb fitted.


Think this was an optional extra with the original 950. The 960 portable which is very much a 950 design has this panel fitted.
Cheers
Brian

 
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Re: HMV 2635 BRC 950 MkII

Post by Focus Diode » Sat Dec 12, 2015 10:14 am

Till, Gary and myself had a great day at Steve's last Monday. Till re-aligned the HMV on 405-lines which is now giving the stunning results these sets are capable of. Unfortunately we forgot to take any photos.
The Ultra 950 has also been delivered which will I'm sure will have its own thread in due course.
The main difference between the 950 and 950 MkII is the EHT arrangement. The original 16kv version has a red Jellypot LOPT with a half wave rectifier tray. The MkII has a more reliable LOPT with a 5-stick EHT tripler. There was also a 950 MkIII I believe which replaced the mains transforer with a dropper. This example must be extremely rare if ever entered mass production.

The data would appear to suggest all 950s will be 16kv regardless of CRT size with 20kv for the MkII. I was a bit alarmed to find a 5-stick tray in the 19" version of the latter on first seeing one!
Cheers
Brian

 
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Re: HMV 2635 BRC 950 MkII

Post by Colourstar » Sat Dec 12, 2015 1:51 pm

Yes indeed, I owe a huge debt of thanks to Brian, Gary and David for their assistance with the HMV. Some expert twiddling under the experienced eye of Herr Eulenspiegel soon had the 405 side running as it should.

Just when things were looking up, there was a moment of consternation when the set seemed to lose signals, with the picture only appearing when the tuner was clunked away and then back, and then only for a few seconds before it vanished. It turned out the PCF80 oscillator in the tuner had decided to throw in the towel. A replacement was sourced from the shed...

I will post a photo of the improved 405 picture very soon.

As to the Ultra Bermuda that I won on ebay and that Gary was kind enough to collect for me, all those years in the attic seem to have seen off the main electrolytic can. More on this in a new thread in due course.

I shall have to plan a visit to the North East in the new year and see exactly what goes on up there... :)

Steve

 
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Re: HMV 2635 BRC 950 MkII

Post by Focus Diode » Sat Dec 12, 2015 2:10 pm

I'd forgotten about the faulty PCF 805 in the tuner. That was a brilliant diagnosis from David. I once had a similar fault on UHF with a set due to the PC97. Tapping the valve in situ caused the problem to come and go, a replacement curing the fault.
On another set I had a curious case of an intermittent blank raster on VHF, sound being normal. A replacement PCF805 cured the problem.

Brian


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