The AM Forum

I realize that testing these tubes in an RF deck is the way to do it, but does anyone know of a similar tube that I can test for in my old Hickok tube tester, just to test for shorts, etc? It's not in the tube charts of my tester. I can test 811's etc, but not the 4x150 (or 4cx250s, etc...probably too new for my tester).

Dave WB4IUY

The 4X150 came out in 1947 and some testers had adaptors available, especially military.

The anode is obvious, the ring below it is the screen and the keyed base center pin is the grid. The little pins include another screen contact and the cathode + filaments.

http://tubedata.milbert.com/sheets/079/7/7034.pdf

I can test it in a 6M xvtr if you want.

Carl

Somewhere amoungst my papers is an article I think from GE about making a tube tester specifically for transmitting tubes.

As best that I recall, that series tube (the 4x, 4cx etc) instructions were very specific
in stating air must be applied even with only filaments lit off.

I don't remember if the adapter with my I-177 has a socket for them or not. It is snowed in
out  in the shop (garage!) and not able to get in there for a week or so...

The Triplett 3444A will test them.  Even though the plate/screen voltage is very low, it seems to be able to tell a good tube from a bad one.  Be careful with the filament current.  Most testers can't handle that amount of filament current.

Thanks for the info on the Triplett. I've got two testers here, but they don't have the 4x150 or variants listed. I have a batch of NIB 4x150s and hardware, and want to build something.with them, if they're OK.

I found that a HUGE percentage of them, including brand new ones, had VERY high heater-cathode leakage.   I was very surprised to find so many were that way.  It could be the tube tester incorrectly measuring the heater-cathode leakage, but there were some tubes that had low or no leakage, so I think the tester is probably accurate.