Professional 625 -> 405 Convertor

[paolo]

Apologies if this has been posted elsewhere or isn't in the right section of the forum, but I thought you might be interested in this video of a very interesting piece of kit

http://www.youtube.com/watch?v=RJVCA2OvQng

Paul

[Steve_P]

So someone actually got one of those to work! My God....

Cheers,

Steve P.

[ppppenguin]

That's the one that belongs to Malcolm Everiss. Getting one of those to work, with its thousands of electrolytics, slightly iffy germanium diodes etc is a mammoth effort. The resistors should mostly be OK. Those chunky looking parts are high stability types, rated at 0.25W I think, and mostly run well within this. The OC140, used in huge numbers here, is a very special transistor. It is symmetrical, the collector and emitter can be interchanged. This makes it ideal as a signal switch. There is no modern equivalent.

Malcolm is also known for the "Domino" 625>405 converter which was the defacto standard until the Aurora arrived.
http://www.domino405.co.uk/

[Parabola]

Phew, is it hot in here or is it just me?

Is this type of video legal? It's like a dirty movie for standards converter fetishists. I'm off for a cold shower.

Wonderful stuff.

Parabola

[ppppenguin]

A couple of pages from the CO6/501 manual. I have a photocopy of the entire manual. It's about 2" thick. Serious hardcore stuff.

Parabola, since you're local it's available on loan

[FERNSEH]

I'm still not sure what I am going to do with this converter. (Pictured) It has not been in use for a long time and is now full of faults which will take some time to sort out. It was constructed late 1989 as a replacement for an earlier converter which was constructed in 1984/5.
The first converter is still in use by a member of this forum.

I use two Auroras now, the first multi-standard version and NTSC405 multi channel unit. Bought to operate with the Pye 405CTV.

DFWB.

[HamishBoxer]

Re Malcolms standards converter,went over to Scarborough years ago in a hired van to pick same up only to find the guy had changed his mind about parting with it!

David

[FERNSEH]

Way back in the late eighties I had a Pye standards converter. It was later passed on to another collector in the South of England.

The reason for not keeping it was that the TV and video trade was booming and there no time available to restore such a mighty piece of equipment. I wonder where that converter is now?

[ppppenguin]

Fernseh (David Boynes) designed and built the first 625>405 converter other than those designed by the BBC. It predated the Dinosaur, Pineapple and David Looser's designs by several years. It was a substantial achievement to do this with the parts available at the time, espeically as David is not a professional design engineer.

[HamishBoxer]

And i remember reading all the updates on that convertor by Fernseh in 405 Alive.Oh, the years go by!

David

[murphyv310]

Of course RTE had the ultimate professional standards converter once their own one chucked it! It was a 405 line camera set up to "see" a picture off a 625 line set!

[ppppenguin]

Originally Posted by murphyv310

.... a 405 line camera set up to "see" a picture off a 625 line set!

This was the original method, as used by the BBC for the first OBs from the continent in the 1950s. It was the only method until the BBC developed the CO6/501 in the early 1960s.

Field rate conversion was a much tougher nut to crack. Optical conversion reigned supreme until the BBC built their first analogue field rate converter in time for the 1968 Mexico Olympics.

[mark pirate]

Just goes to show what an amazing piece of kit an aurora is

Mark

[murphyv310]

Too right Mark, every time I have my sets on I really can not comprehend what Darryl has designed and produced, a totally amazing feat.

[Heatercathodeshort]

Totally agree! It is so perfect that I sometimes think 405 is still being transmitted!
The amazing thing is I cannot remember the converted 405 line signal provided by one of these Goliath units breaking down. The picture was slightly 'different' to the original live signal but of excellent quality and served us very well. Simply amazing bit of kit. Regards, John.

[ppppenguin]

Towards the end of 405 TX the maintenance on the converters was, shall we say, a bit negelected. This would have been less serious on BBC1 where the later digital CO6/509 was a pretty reliable machine. It was designed specifically because the the BBC thought that the 405 service would outlast the reasonable service life of the CO6/501. ITV soldiered on with Pye built CO6/501 all the way to the end.

PS: I suspect the converters at Crystal Palace and Croydon would have received better attention than most others. The usual London effect.

[murphyv310]

The pictures on 405 lines BBC1 from Kirk O' Shotts on Ch3 & STV from Blackhill on Ch10 were always spot on even in the last few months of 405.
I lost some interest in vintage radio & TV about that time but had seen 405 a few times before the closure and it was always good.

[Ray Cooper]

Originally Posted by Heatercathodeshort

...The amazing thing is I cannot remember the converted 405 line signal provided by one of these Goliath units breaking down....Simply amazing bit of kit...

Can't you remember, though? The further you got from the converter, the less the perceived hassle: as one of the poor blokes standing next to the damned thing and trying to keep it running, I have to report that my mileage differed from yours.

What you may not appreciate was, that at any given station, there'd be two of the things running in parallel, with a bloke constantly on hand to switch from one to the other if the 'service' unit started to display eccentric tendencies, which they certainly did on a weekly basis and sometimes daily. In bad periods, it could be a struggle to keep even one of the units in good working fettle. However, with a mixture of experience and deep cunning the service was usually maintained to an acceptable standard.

Also, bear in mind that you'd be viewing the end results on a domestic telly, as like as not: we were looking at the goods using professional studio monitors (Pye 2780 actually) which gave superb pictures upon which any defects were screamingly obvious...

[ppppenguin]

Originally Posted by Ray Cooper

What you may not appreciate was, that at any given station, there'd be two of the things running in parallel, with a bloke constantly on hand to switch from one to the other if the 'service' unit started to display eccentric tendencies, which they certainly did on a weekly basis and sometimes daily. In bad periods, it could be a struggle to keep even one of the units in good working fettle. However, with a mixture of experience and deep cunning the service was usually maintained to an acceptable standard.

Was it like this for the CO6/501 analogue or CO6/509 digital? I would have hoped that the '509 could run for long periods without attention.

[Ray Cooper]

Originally Posted by ppppenguin

...Was it like this for the CO6/501 analogue or CO6/509 digital?...

I can only speak for what happened at Sutton, but no, for all of the time we ran with the old analogue converters. Towards the end of things, a secondhand 509 appeared - I think released when Llanddona closed on 405 - just in case the analogue converters collapsed terminally, but I can't recollect it ever being used in service. We'd largely got the measure of the analogue beasties, we had a cupboard full of OC139s with little purple spots on the end, and plenty of
polystyrene capacitors, and there was far too much going on at that time to sort out the foibles of a new bit of tackle that'd likely not be needed (I recall that when we did try our specimen of 509, we found that it wasn't entirely without defects itself...)