[rd48sec]

I am in need of two new type  41 tubes (from a 41-290 Philco).  Is this the replacement?

https://www.tubesandmore.com/products/41...e-st-glass

Thanks for the help!

[Radioroslyn]

Yup...

[mikethedruid]

The ST refers to the glass envelope. It means a tubular envelope. It will be a constant diameter all the way from the base up, rather than bulging like a regular 41G. It is a direct replacement despite looking different because of the envelope.

[sdradioman]

I thought ST stood for “shouldered type”, and the GT type was the consistent diameter type? ST and G are the same thing and GT was the later, non-shouldered glass versions?

[madsowry]

Best place I've found to get tubes:  findatube.com     Bob Dobush has tons of tubes and I checked;  41 new $6.50  used  $3.00.  Hope this helps.

Dick

[mikethedruid]

ST is not actually a standard abbreviation. I believe I saw it on only one tube I ordered which was Russian made. G is what you call "shoulder type, GT is the later, smaller, straight side version, and later many GT types are marked GT/G to save confusion, clearly showing it replaces either. Except for looks they are the same , BUT, if there is NO SUFFIX, and the tube has a metal outside, it can be a problem in Philco radios. These metal tubes use the case as an RF shield, and it connects to a pin that is connected to the ground plane of the radio. Philco radios use the G or GT types which do not use this pin, and so use the socket solder lug as a tie point, which can be live, so you can't use a metal tube in Philcos safely, metal does not substitute for a G or GT type. This is why many RCA radios don't use tube shields for their RF, oscillator, and IF tubes, the metal tube IS the shield, but Philcos and other radios use those shields and G or GT tubes.

[captainclock1988]

Except for looks they are the same , BUT, if there is NO SUFFIX, and the tube has a metal outside, it can be a problem in Philco radios. These metal tubes use the case as an RF shield, and it connects to a pin that is connected to the ground plane of the radio. Philco radios use the G or GT types which do not use this pin, and so use the socket solder lug as a tie point, which can be live, so you can't use a metal tube in Philcos safely, metal does not substitute for a G or GT type. This is why many RCA radios don't use tube shields for their RF, oscillator, and IF tubes, the metal tube IS the shield, but Philcos and other radios use those shields and G or GT tubes.

Hi Mike, does this also apply to Zenith radios as well? 
I'm wondering because I have a 1942 Zenith 10S690 Radio that all of the tubes in the radio are of the G type variety of tubes and all of the critical tubes in the set had shields around them, there was one tube in my Zenith that was replaced at one point in time that was replaced with a metal cased tube and the original tube shield was tossed when they installed that metal cased tube into the radio (the radio other than the 6A8 tube and the 5Y4G tube has all of its original Zenith tubes in it yet).

[mikethedruid]

Pull out the chassis and the metal tube, with the radio unplugged, of course. Then ring out between pin 1 and ground, as well as between pin 1 and the other 7 pins. Pin 1 should either not be connected to anything, or it should be connected to ground. If it is connected any other way, the tube should be a G or GT type, not a metal tube.