Help to ID a tube

[Hi Fi and I]

Hi, please help me to ID this tube:
Thank you!

 

[Hi-FiGuy]

That looks like a 5U4G rectifier, it could be a 5R4G

 

[knockbill]

Says 5Z3 on the base,,, https://frank.pocnet.net/sheets/021/5/5Z3.pdf

 

[GregBilodeau]

I would bet that it is a 5U4G

Gregb

 

[arts]

Says 5Z3 on the base,,, https://frank.pocnet.net/sheets/021/5/5Z3.pdf

The 5Z3 base is just another tube visible in the picture. The 5Z3 is a 4 pin base.The tube he is asking about is an octal.

 

[gadget73]

5U4G or maybe (I doubt it) A 5Y3. Plate structure looks too long to be a 5Y3 though.

 

[Hi Fi and I]

Thank you!

 

[knockbill]

The 5Z3 base is just an other tube visible in the picture. The 5Z3 is a 4 pin base.The tube he is asking about is an octal.

HA,,, got one outta two anyways!!! 5U4 could be a good guess,,, match the plates to a known 5U4 and see how it tests..

 

[primosounds]

Put the tube in the freezer for a few minutes and when you take it out check on the side for the tube designation. You only have a few seconds when the numbers will be visible.

 

[knockbill]

5R4,,, 5U4,,, 5V4 for comparison... 5R4 is missing teh key...

 

[Pio1980]

5U4G.

 

[EastPoint]

That’s a 1952 RCA 5U4G. A 5Y3 would be smaller and one from that era wouldn’t have the coke-bottle glass. An RCA 5R4 from that era would probably have a brown base and would look different. A 5V4 would be smaller and would have a different internal structure. A 5Z3 has four pins instead of the octal base.

 

[soundmotor]

Put the tube in the freezer for a few minutes and when you take it out check on the side for the tube designation. You only have a few seconds when the numbers will be visible.

Fogging it with your breath sometimes works also.