TV day at Dulwich - 10th Sept

[ppppenguin]

On Saturday 10th September there will be a special TV** day at the Vintage Wireless Museum. Celebrating the 80th anniversary of the BBC TV service which started on 2nd November 1936. Rather oddly it's not on either the BVWS or Museum websites.

Our resident Geordie mentioned it here:
http://golbornevintageradio.co.uk/forum/...p?tid=5482

Everyone welcome, admission £10 which I think includes a light lunch.

I'll be there as part of the crew.


**I don't think they mean this sort of TV though I reckon John Wakely could play Eddy pretty well: https://www.youtube.com/watch?v=ZCZDWZFtyWY

[Murphyv310]

Is there anything planned on BBC TV for this anniversary on the 2nd Nov do we know?

There are things happening ooop norf when Mike (Radiomike, Mikeymushradio) on the following day after the TV day Jeffrey when hopefully the HMV 900 will be fired up and display a picture, Mikes place is in Cramlington and all will be welcome.
Date for dairy Sunday 11th September.

[ppppenguin]

Earlier this year I was involved in the making of a programme that will be shown on BBC4 later this year. My ugly mug may be scaring the public again but I'm not sure yet. One thing that was wonderful in the production was that they had a small orchestra and a singer doing the Television Song. "Oh mighty maze of mystic magic rays..." We all know this from TV comes to London but I doubt it's been performed since so hearing it live was quite spine tingling. I chatted to the singer and said she was probably giving the first performance since 1936.

[ppppenguin]

Another reminder of the TV day this Saturday. More details and discussion here:

http://www.vintage-radio.net/forum/showt...post876000

[Raditechman]

It must have been nice to hear a live performance of "Oh mighty maze of mystic magic rays".  I look forward to hearing it in good quality sound when the programme is broadcast.
I have played it on rare occasions on the piano and try and sing along to it, so it has had a private performance since 1936!.

I have 3 events lined up for Saturday, (it is a day when several churches are opening up their bell towers for anyone to try ringing) and not having a car I will not get to the Museum TV day,  if I had transport I would have taken along a 17" KB Queen.

Hope you have an enjoyable and successful day.

John

[Terry]

An excellent day today, despite the constant drizzle - it could have been much worse!

Never seen so many old sets working together before. Some had to be turned off mid-afternoon when the conduit carrying the incoming mains was found to be getting rather hot!

I noticed a Sobell with a pronounced switch off spot after this. It obviously uses the on/off switch for switch off spot suppression* but this doesn't work when the mains supply is interrupted externally. It might be a good idea to modify it to an alternative method of suppression to protect the tube.

* I assume it uses the method whereby the earthy end of the brightness control circuit is returned to the mains input side of the switch. With the switch on it is, of course, connected to the chassis but, when it is switched off the circuit floats effectively turning the brightness up full so as to discharge the EHT quickly while the scan is collapsing.

[Red to black]

Hi Terry,
The spot suppression mod could be done easily and reversible with a simple relay.

[ppppenguin]

As Terry said, it was a great day. On the TV engineering side full credit must go to John Wakely and Peter Sanders who perform the Sisyphean task of keeping the TV display in good order. Due recognition for all the team. Eileen in overall charge, Dave Grant, Richard Stowe, Chris Rowe. Apologies to any who I have failed to mention.

I went to the final maintenance session on the Friday evening before the event. We finally tracked down the intermittent hum that was afflicting BBC1. This has been annoying us for several weeks, if not months. At first I thought the PSU for the Auroras was a bit iffy and changed it. Then I swapped out the BBC1 Aurora so I could look at it on my bench at home. It's a very early one which can suffer hum problems due to a peculiarity of the modulator chips. I changed the 2 relevant resistors and took it back with me on Friday. John Wakely said that he'd seen the hum with the repalcement Aurora which was known to be OK so back to square one.

I forget whether it was John or Peter who had the brainwave, observing that the hum appeared when one group of sets was switched on. We unplugged them one by one until we found the guilty set. A Pye LV20. I've attached a partial circuit of the almost identical B18T. John soon found a problem with the aerial input. This resulted in what was probably a neutral earth short and lots of 50Hz flowing round the co-axial outers of the aerial distribution. It was going to be intermittent because the neutral potential is always variable wrt earth. If the set's mains had been reversed the result would have been a blown fuse and hopefully no further damage.

[Refugee]

Why did the RCCD not trip?
Ours does if we get a N-E short.

[ppppenguin]

What RCD? These are unknown at the Museum Some work is needed on the electrical installation at the Museum but I'd rather not discuss it in open forum.