Any ideas what this is, help identify.

[Globalgrid]

Any ideas, especially the white glass block component, I'm sure someone will let me know what it is .
On the side it has controls Line shift, 405 Focus,625 Focus,Line linearity,Width.

It also has with it two large caged power supplies.

Curious to find out.

Thank you.

[ms660]

It's an old colour TV chassis (dual standard) looks like a Decca, the glass block is a delay line in the chrominance circuit (64uS (64 micro second) delay)

Lawrence.

[toshiba tony]

Certainly not a model I recognise, but I'll be watching.

[duncanlowe]

Likewise, the fact that it has 405 and 625 says to me a dual standard TV receiver. I guess that it was only colour in 625 mode though? And yes the glass bit looks like a delay line to me that I've seen many years ago before I shied away from TVs ('cos they hurt'). It must be early though, given that colour was rare back in the day of dual standard models, wasn't it?My parents first TV was dual standard, but most definately monochrome in both modes.

[ms660]

I was too late with the edit in my previous post to do a link so here it is (Decca CTV25):

https://www.vintage-radio.net/forum/...ad.php?t=27126

Lawrence

[toshiba tony]

Worked on G6, GEC and Pye dual standard but never got to see this one, it looked a monster to work on. The G6 didn't scare me but I think this one would have done.

[ms660]

I wonder how many techs. defeated the interlock.

Lawrence.

[Globalgrid]

Thanks for the response so far, and the power supplies there are two of these.

[toshiba tony]

Re the shield interlock switches, we were warned NEVER defeat them. Since then I have carried lunacy procedures out and have managed 65 years of age. But has anyone really suffered from injury regarding open cages. Living dangerously has always been my thing but I was always careful with colour valve eht sections.

[ms660]

Originally Posted by toshiba tony

Re the shield interlock switches, we were warned NEVER defeat them. Since then I have carried lunacy procedures out

You're not alone...

Lawrence.

[G6Tanuki]

Seeing those large power-supplies, I wonder if this was maybe a TV chassis intended for use in schools/colleges etc or as a monitir, where isolated-chassis was needed rather than the direct-mains-rectification and series-heater-string techniques used in consumer TVs.

[ms660]

Originally Posted by G6Tanuki

Seeing those large power-supplies, I wonder if this was maybe a TV chassis intended for use in schools/colleges etc or as a monitir, where isolated-chassis was needed rather than the direct-mains-rectification and series-heater-string techniques used in consumer TVs.

Live chassis, auto transformer (except for CRT heater) if it's anything like this schematic (Page 192, Fig. 148):

http://the-eye.eu/public/Books/Elect...icing_text.pdf

Lawrence.

[Restoration73]

ISTR the problem with the early valve eht systems (PL509, PD500, GY501) was the risk
of X-ray radiation. It was recommended that the operating stage was viewed through
lead glass (i.e. absorber)

[G6Tanuki]

Ah, I sorta assumed the big transformers/capacitors were for a classic isolated mains-PSU.

From memory the X-ray issue with early colo(u)r TVs largely came from the EHT shunt-stabiliser valve, which usually had 20KV or so on the anode and so when the electrons decellerated at the anode they created "Bremsstrahlung".

I remember quite a few early colour tellies had a screen round the shunt-stabiliser valve. Later colour-tellies seemed to manage quite well without the shunt-stabiliser valve.

[Malcolm G6ANZ]

The x-rays from a 25kv supply are very soft. I would be surprised if they could penetrate the glass envelope.
I worked on an ancient x-ray machine that produced 25 -50kv x-rays and was used for treating the skin surface as these x-rays could not penetrate more that several mm. From this I think that the manufacturers were just playing very carefully.
Looking at the construction of the PD500 the anode completely surrounds the cathode since the x-rays generated when the electrons hit the anode come off at and angle back to the cathode it is difficult for them to escape. I'm not saying that there are no x-rays generated and escape to the surroundings just that the amount and their energy will be low. Still wise to take precautions though.

Malcolm

[bobbyball]

Decca "Battersea" chassis as used in, for example, Model CTV25. These sets were as wide as a wardrobe if the console model.

[MotorBikeLes]

Going back 40 years, I was asked to fix an early Korting CTV, the model with two PL509s. The picture was small and shimmering, but as I had a Marconi EHT probe with my 1041C, I connected that up and switched on.35KV.
I knew about PD500s, X-radiation Bremstrahlung (braking) radiation, but was still quite green regarding my foray into CTVs. I advised the owner that I could not repair it, and either go the the Korting main agents, or scrap it and get something newer.
They had a Grundig 5010 off me if I remember.
Les.

Soft X-Rays are quite dangerous, they stop just inside the body doing damage, at least hard ones mainly go right through. Dad was a radiographer and said the "shoe X-ray machines" where particularly dangerous, softish rays and looking down on the tube too.

[TonyDuell]

I seem to remember that the problem with valve-rectified EHT supplies was that the valve had a fairly high effective impedance and thus the EHT voltage varied with beam current. In a colour TV this could make a mess of purity/convergence when the average picture intensity changed. The shunt stabiliser triode was used to provide a constant load on the EHT supply so that the voltage was also constant.

It was not needed with supplies that used semiconductor diodes, for example in a tripler module. Nor with the B&O 2600/3200 sets which had separate line output and EHT generator stages, the drive to the latter being controlled to stabilise the EHT.

I am always surprised that the GY501 rectifier diode is claimed to be an X-ray emitter. When it is forward biased it is not dropping enough voltage to produce significant X-ray emission. When it is reverse biased it is not passing much current. So when does it produce X-rays? None-the-less there was a warning printed on the glass envelope of the one I saw.

[Malcolm G6ANZ]

I agree that any x-ray can be dangerous. My argument is that the 'shoe x-ray machines' and other similar devices are specifically designed to emit x-rays through a window. The PD500 and similar only produce x-rays by default. There is no designed way for the x-rays to leave the tube so any emitted are by 'accident'.