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Vintage Television and Video Vintage television and video equipment, programmes, VCRs etc.

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Old 6th Nov 2021, 10:09 am   #21
raditechman
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Default Re: Rediffusion MK 7

The sets is a Sheerline, always off putting on a service call when at Rediffusion
The MK 8 was much better.

John
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Old 6th Nov 2021, 10:31 am   #22
dazzlevision
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Default Re: Rediffusion MK 7

Quote:
Originally Posted by thermionic View Post
Quote:
Originally Posted by 19Seventy7 View Post
Oh that's interesting, I'm sure i read 'plessey' on a PCB within the set but I may have imagined that......
Thanks
'77
It’s possible you saw ‘Pressac’ on the PCB, as that company manufactured PCB panels and other parts for the Radio & TV industry.

I’m sure if Dazzlevision sees this post, then he’ll be able to provide some information.

Cheers.

SimonT.
Yes indeed, Pressac did make PCBs for TV and radio manufacturers:

Pressac. Based in Leopold Street, Long Eaton, Nottingham. Pressac were manufacturers of connectors for use in the consumer electronics industry. They made the (angled) “two flat blade” mains lead connector favoured by Philips in the 1960s (also in the G8 CCTV chassis) and the PCB connectors used in the Decca 80/100, Philips G11 and Rank T20 colour TV chassis. They also made PCB’s – as used in RBM sets of the late 70’s. Nowadays, they have moved into manufacture of components for the car industry.

I see the letters "TCC" on the copper side of one of the PCBs in your set. TCC = Telegraph Condenser Company (taken over by Plessey in the early 1960) a major UK capacitor manufacturer. TCC made PCBs in the late 50s/early 60s.

Another PCB manufacturer that you'll see in sets from the 1960s and 70s is Mills & Rockleys. Mills & Rockleys (Electronics) Ltd, Swan Lane, Coventry (in 1960 & 62). The PCB division of Mills & Rockleys (Production) Ltd. The "M R" logo was often etched onto the copper side. Murphy Radio - later Rank Bush Murphy used them a lot.
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Old 6th Nov 2021, 4:25 pm   #23
Vintage Engr
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Default Re: Rediffusion MK 7

I seem to remember that most of the reservoir/smoothing caps on these were indeed Plessey.
Long while ago, I dread to think how many of these sets I serviced on a late shift!

David.
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Old 6th Nov 2021, 4:28 pm   #24
Vintage Engr
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Default Re: Rediffusion MK 7

Quote:
Originally Posted by raditechman View Post
The sets is a Sheerline, always off putting on a service call when at Rediffusion
The MK 8 was much better.

John
I've just found an old Redihire service card, & on the back I've drawn out the pinouts for a mark 8 LOPT...
Very useful!

David.
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Old 7th Nov 2021, 12:12 pm   #25
19Seventy7
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Default Re: Rediffusion MK 7

No PCB mentions Plessey, so not sure where I got that from! Only TCC was on the PCB, like you say. I'm not sure what the reservoir/smoothing cap is on this set as the print side is face down. I'm fairly sure theres a handful of TCC electrolytics dotted around, though.

Thanks
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Old 2nd Dec 2021, 8:09 pm   #26
19Seventy7
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Default Re: Rediffusion MK 7

A couple weeks ago Vintage Engr dropped by for a visit to have a look at the set. We (I say we, I mean David!) had the set in bits, cleaning all the contacts, testing all sorts. We got to the point of switch on, flick the switch and up goes a resistor. Switch off and call it a day. May not have had the outcome we wanted but it was a good learning exercise for me. We decided it was best to replace the caps around the resistor and to retry, so that takes us to today.

I replaced all six 0.1uFs and the singular 0.25uF wax caps on the IF board, along with the resistor and give it a run up through my lamp limiter. Nothing. I gave the set a check over to find an edge connector wasn't fully connected. Run up again. Nothing. I took the lamp limiter out of circuit and gave her full mains. The heaters slowly come up, then sound rustles up, then a nice healthy sounding line whistle. No picture though. I think the brightness is up full but I go to make sure, I put my hand on the brightness control and a flash on screen, I hold the control in place and get a nice and bright, although collapsed, raster! Brilliant. It's a great feeling to see a CRT light up for the first time in how ever many years

I still have all of the wax caps to change on the other PCB and a tuner to source and fit, but I'm really pleased with the progress made.

Apologies for the poor photo, it was the best I could get

Thanks
'77
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Old 4th Dec 2021, 4:04 pm   #27
Vintage Engr
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Default Re: Rediffusion MK 7

I said the CRT would probably be o.k., and it appears to be, Great, well done.

Looking at your photo, apart from the off-axis deflection coils, the signs are pretty good.

I'll P.M. you with the tuner idea, as it might get a bit involved.

David.
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Old 4th Dec 2021, 7:23 pm   #28
19Seventy7
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Default Re: Rediffusion MK 7

I’m glad it is. I did think it would be too judging by the gun, but can never be too sure. I’m not surprised the scan coils are wonky as I took them off to remove the chassis as the plug was stuck solid, but soon sorted that.

I’ll get to replacing the wax caps on the time base panel, and take it from there. Getting exciting now!

Thanks
‘77
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Old 21st Dec 2021, 1:47 am   #29
19Seventy7
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Default Re: Rediffusion MK 7

Quick update

The timebase panel on this set has now been recapped, but this will most likely be redone in some segments to make a tidier job as I had to make up some values.

However now I don't get a raster, even when rocking the brightness control, so will investigate that. when I switch off I do get a bouncy frame collapse that slows to a stable dot. However the brightness control has an effect on the dot so I believe the brightness control is okay.

Vintage Engr has been able to source a replacement switchbank and VHF tuner and has kindly offered to assemble this for me, ready to fit into the set, which is great, so that's something to look forward to

Thanks
'77
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