I am about to remove the safety glass from a roundie(original '63 RCA hec). I know most everything about the process but I wish I could obtain whatever that material is to put it back properly. Without it I guess I will do a bead of silicone with four spacers. I am concerned it will be visible that the glass and safety glass are seperate. I am guessing that stuff comes in sheets and is probably put on the tube hot and then the safety glass must be pressed on.
I bet somebody here knows!
I am still trying to figure out how to get photos of three old sets I am restoring.
Thanks and have a nice day! John

I have used bits of popsicle sticks as spacers and you cannot tell there is a gap. I think you could probably go with less of a spacer if you wanted. The consensus from the last time this was discussed was that the original material was thin, like water, and was poured in after the edges were taped. I'm not sure where you would find such a product today.

From what I can see from old 21" tubes there is a small opening (that was later plugged) on the tape surrounding the tube where the pva was injected into. (If it were just poured in there would be an issue with air bubbles I would think)
This is what I was told anyway, have never actually seen it done at the factory. The tube/lens will look fine without the pva but will not be as safe as it was intended to be without it.

Somebody should eMail a CRT rebuilder with this question... All the ones I knew here in LA (now LONG gone anyway), would remove the safety glass and NOT reinstall it. In place of the glass, they applied a steel band around the circumference of the tube. This was supposed to cause an imploding tube to be contained and not ricochet out into the room.

But I hear that Hawkeye, and maybe some other big rebuilders, DO reinstall the gel-spaced glass.

Charles

There are factory made 21FBP22's with a round safety glass attached around the outside of the tube only (no resin between safety glass) so the result is like a 21FJP22 with no PVA. I have one of these on a Zenith.

Somebody should eMail a CRT rebuilder with this question... All the ones I knew here in LA (now LONG gone anyway), would remove the safety glass and NOT reinstall it. In place of the glass, they applied a steel band around the circumference of the tube. This was supposed to cause an imploding tube to be contained and not ricochet out into the room.

Charles
I don't know enough about tubes designed for banding vs. tubes not designed for it - that would scare me a little (like, could you apply too much pressure to a tube not designed for it, and make it less safe?). - Wayne

I hope to find out if I can aquire whatever liquid stuff that gel layer may be.
Seems like it would be used for other things as well.



On this CTC-15, is it normal for the CRT filaments to come on too bright then quickly go to normal glow when power is first turned on? I think I remember it being that way but I was a kid when I last saw one around '80.
Thanks, John

I hope to find out if I can aquire whatever liquid stuff that gel layer may be.
Seems like it would be used for other things as well.



On this CTC-15, is it normal for the CRT filaments to come on too bright then quickly go to normal glow when power is first turned on? I think I remember it being that way but I was a kid when I last saw one around '80.
Thanks, John


I don't believe so... That's a parallel filament circuit, and the CRT filaments should warm up normally. If it were a series set, I'd OK it because in a series set, there will be some filaments in the string which will light faster than others, so those staying cold longer (less resistance) will dissipate all the current across the ones that warmed up earlier (more resistance). Probably nothing to be worried about, though. Just to be safe, hook an AC voltmeter across the filament wires to the CRT and watch the readings as it warms up. See if somehow the filament voltage is surging. If so, it might be a fault such as an open ground on the power transformer, or possibly there is a thermistor in the CRT filament circuit that might be shorted. I can't remember if there is one.

Charles