12М1М_Triode-Pentode12m1m_Triode-Pentode

This tube looks to be a double tetrode. It has three grids, but the third grid is connected to anode, as red arrow show on photo.

Anexos

• 3rd grid connections (145 KB)

Your foto indeed shows a tube with a double system of identical systems.

However, the 12M1M is found in the "Electronic Universal Vade-Mecum, Vol 1, Wydawnictwa Naukowo-Techniczne, Warszawa, 1964".

Here, the 12M1M is a Triode - Penthode.

Probably, the type printed on the bulb of your specimen is erranious?

Regards,

Dietmar

Yes, I owe this book, and realised that it has some errors and mifinformations, maybe this is one of them. 12М1М is clearly a double pentode, I recently buy this tubes (photos uploaded) and it is easily visible. Photos uploaded by Ernst Erb also depicts double pentode with 3rd grid connected with anode.

I have moved the pictures to the 12M1M double pentode.

Probably there are two different tubes with the same designation 12M1M or one of them is an error in the data books.

These links always calls the 12м1м as double output pentode:

Приемно-усилительные лампы

Лампы и панельки

АудиоПортал
 

the information given in the Electronic Universal Vade-Mecum appears to be wrong.

I don't understand why the third grid is connected to anode. How can this tube operate as output pentode then ?

Best Regards,
Jacob