At 02:14 PM 7/27/2007, you wrote: Ah, so I was burning the hydrogen gas, and exposing myself to toxic barium compounds. :-) - John

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Chuck Guzis wrote: It's being done off-the-shelf: http://unitednuclear.com/xray.htm Cheers, Chris. - -- Chris Kennedy chris at mainecoon.com AF6AP http://www.mainecoon.com PGP KeyID 108DAB97 PGP fingerprint: 4E99 10B6 7253 B048 6685 6CBC 55E1 20A3 108D AB97 "Mr. McKittrick, after careful consideration..."

On 27 Jul 2007 at 23:29, Tony Duell wrote: I seem to recall the early color sets here had X-ray warning stickers on the HV regulator cage (and it was always a metal cage), but you rarely saw them on the monochrome sets. 6KB4 was the most common type--a large, octal-based unit with a peculiar cup-shaped grid more or less completely covering the cathode at the bottom of the tube and about a 3/8" air gap between that and the long tubular anode (like that on a 1B3, but much larger) connected to the top cap. Rated for something like 20-30KV if memory serves and about 30W plate dissipation. Cheers, Chuck

It should be noted that 6BK4Cs still have a little value, as they are used in, of all places, some older semiconductor fab machines. -- Will

Contrary to what some books said, I do not belive the EHT rectifier valve, even in a colour TV, was a major source of X-rays. As I understand, it, the energy ('hardness' ;-)) of the X-rays depends on the accelerating voltage across the X-ray tube, the intensity depends on the current. There simply isn't that high a voltage drop across the rectifier valve when it's forward-baised to produce hard X-rays. And of course when it's reverse-biased, the current is minimal. Therefore I do not beleive the lower EHT in a monochrome set (15kV as against 25kV) is the reason that said sets don't have an X-ray warning on the EHT cage. Now the shunt stabiliser valve had the full 25kV EHT across it, and was passing 1mA or so. That would be enough to produce soft X-rays. Of course monochrome TVs didn't have such a device, so no X-ray problems there. Interestingly, while I've seen X-ray warnigns, and even interlock switches on the EHT cage of sets that used a shunt stabiliser, there was nothing on the EHT cage of that set I mentioned last night which had the 2 output stanges and no stabiliser.triode.Presubably becuase there was nothing in that EHT cage to produce significant X-rays. TV valves seen very continent-specific. The UK (and AFAIK European) sets almost always used a PD500. This was a big triode, constructed roughly as you've described but with a B9D base. This, also called a 'Magnoval' was an all-glass base, similar to the well-known B9A (Noval) base (think of a 12AX7 or similar), but about twice the diameter. Polarised by a wide gap between 2 of the pins, not a certnal locator like the octal base. The line output valve ('horixontal output tube' to you :-)), in colour sets and later monochrome sets had the same base (the valves being the PL504 and PL509 respectively). Earler sets used the PL81 (B9A base, IMHO thios valve was massively under-rated, and failed far too often), and before that the 30P4/PL36 on an octal base. Colour TVs used a PY500A boster diode ('damper tube'), again on the B9D base. Monochrome sets used a PY800 (B9A base), and before that the U191/PY31 (octal base). Note that in the UK, most booster diodes had the _cathode_ connected to the top cap. Colour TVs that used a valve rectifier almost always used the GY501 (again on a B9D base). Monochrome sets might use a B9A-based rectifier (DY86, EY86, KY80, etc), or a wire-ended one, soldered in place (EY51, etc). Almost all UK TVs had series-string heaters, the first letter 'P' of the valve number meaning '300 mA heater'. The next letters indicated the electrode structure, D = power triode, L = power pentode, Y = half-wave rectifier, etc. The first digit gives the base -- '8' meaning a B9A base, '5' meaning intitially a B9G base (like a 9 pin Loctal, think of the EF50 used in a lot of military equipment), then used for some wire-ended types, and finally, when 3-digit numbers were introduced, it was used for the b9D base. Note that, of course, the EHT rectiifer diode's filament was not included in the series string. It was powered from a little winding on the line output transformer (flyback transformer). Which explains why 'D' (1.4V), 'E' (6.3V), 'K' (2V) and 'G' (origianlly 5V, but later used for just about anything -- IIRC the GY501 has a 3.15V filament) turn up here. SOunds to be similar ratings to the PD500. That was rated for 25kV on the anode, certainly, and I've heard a current of 1mA or so. The question why can I remember all this stuff. And why do I have service maniuals for 405-line System A TVs on the shelf still... -tony

On Saturday 28 July 2007 18:48, dwight elvey wrote: Back when I was fixing TVs there were a bunch that had that setup, typically a 3A3 for a HV rectifier and a 6BK4 (?) for a regulator. If the set had been running a bunch of years with no service, those two would be somewhat dark, in terms of the glass actually turning a muddy color. The regulator was *always* a lot darker than the rectifier. -- Member of the toughest, meanest, deadliest, most unrelenting -- and ablest -- form of life in this section of space, ?a critter that can be killed but can't be tamed. ?--Robert A. Heinlein, "The Puppet Masters" - Information is more dangerous than cannon to a society ruled by lies. --James M Dakin