FJP=bonded
FBP=non-bonded
Either one with the safety glass removed will look identical, the tint of the screen will let you know which phosphors are in it. Green=sulphide, paper white=rare earth. That's the way I understand it. The RCA sheet I am reading says the 21FBP22 is an all sulphide tube, but I had a rebuilt one that said right on the side of the box 'rare earth' with a grey screen... So perhaps the FBP's came in both flavors, or it could be that a rare earth tube that was bonded in effect becomes an FBP once the lens is removed.
Quote:
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Originally Posted by tomcomm
#1 Why do I insist on running the new FBX and the old CRT at “extreme” ultor voltages? Well RCA and GE 21FBP22 spec sheets specify max operation at 27.5KV. This level is undoubtedly driven by fussy Government X-ray mandate. The specs also notes: “Brilliance and definition decrease with decreasing ultor voltage.” Enough said?
Since brilliance and definition increase is what I’m after why shouldn’t I run at 30Kv (109%max) on a new “modern” FBX that requires only 200ma HOT current, at a winding temp of only 112degF! This new FBX is like a brick compared to the fragile original CTC2B FBX that ran 28KV at 264ma HOT.
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RE: x-rays
The spec sheet carries a specific warning for shielding, even when operated at it's max ultor voltage of 'only' 27.5kv. Going over that limit implies additional risk of increased production of x-rays, so you're taking your chances. The other very good reason not to push too much voltage is not to protect the chassis, but to protect the tube itself. When the HV is increased, so does risk of internal arc within the tube. If you don't much care about the chassis or tube (or your testicles), I don't suppose it matters.
Also the 6BK4C shunt regulator sheet rates 'absolute max' plate voltage at 27kv, for the same reasons as the CRT.
RE: brilliance
This is what the spec sheet says:
"Brilliance and definition decrease with decreasing ultor voltage.
In general, the ultor voltage should not be less than 20,000 volts."
(the part you left out is in bold, because context matters)
Since the tube is specified to be run between 20-27.5kv, I interpret this to mean that when run at voltages lower than 20kv brightness will decrease. RCA themselves only applied 19.5kv to the early picture tubes with the CTC-5 chassis, so there's some wiggle room on the low end when you are hoping to preserve some level of performance. Where your logic runs amok is assuming that it's all good to use the same wiggle room rule at the upper end, when the reality is that maximum ratings should
never be exceeded for safety reasons. I am also a mechanic, I can tell you that the same logic will not fly in engines. "it's good at 10 lbs of boost, there is no problem running 15 lbs through it." I promise you this is not the case, many people have melted expensive parts with that kind of thinking. With high voltage and vintage electronics in close proximity to your body, the chances of walking away from a 'wreck' are not as good as with a car that has air bags. Hope my analogy makes sense, it's about safety more than anything else. I fear for your safety, guess that makes me the 'attack dog' as you put it in your other thread. So be it, at least I said something. I have washed my hands of this.