I found this mixed in with a box of used tubes; it is a Philco, 2" face, 7" long, octal base, no anode connection. So far my search hasn't turned up anything. I read a few discussions referencing Philco projection tubes but they didn't give a size. The only marking I can find is "2152" and it looks like a date code. I'm sure somebody here knows.

Osciliscope tube.
Bill Cahill

Could you hold the face against against a compact fluorescent lamp, then immediately look at the tube
in the dark and see what color the phosphor glows with?

It's a 902Px, x would signify phosphor color. P1= Green, P4=White, P5=Blue.

The "2152" is Philco's "House" number for the 902 CRT, it was used in the Model 022 scope circa 1938.

The Philco projection CRT's are 4" and marked TP400

Prior to WW2, Philco offered a goofy looking 2 inch scope with screen on side and knobs on the front. That is probably the tube and Chuck's 902P1, for green, is right.

All the scopes Philco sold after WW2 used CRTs with more pins on the socket. None were octals.

The projection tube, TP400, has a unique look and is magnetic deflection. That tube is electrostatic. Don

The model 022 is one scope I don't have in my collection but here is one from the Early Television Museum:

Great information! I'll have to find a pinout and see how it tests. I'd assume the filament is either side of the keyway, as usual? 6v?
Thanks all!

Edit: I tried it with the single CFL I have in the house; the lamp has more persistance than the crt so it was hard to tell anything, but I have a little desk lamp with a halogen bulb and I could kinda tell with that. It looked like P1 green to me, though there might have been a more yellow cast. Not an exact test, of course.

Tube pinout and info here:

http://www.mif.pg.gda.pl/homepages/fran ... 9/902A.pdf