Tube: EM-11 (6U5G) Magic Eye tube (tunning tube)

“A Tuning eye (tube or valve), is a tube that gives a visual indication for audio output, signal strength or other functions. It is also called cat’s eye, or tuning eye tube. They were fitted on radio receivers from around 1936 onwards, replacing the earlier “Tuneon” neon lamp type tuning indicators, as a novel selling feature.” (Source

I managed to acquire a Tesla EM-11 Tube these days. It’s used, but in great shape. I plan to build a simple circuit to see it working. Here are some pictures: Em11-ani

More details on this tube are available on RadioMuseum.

The schematics for the circuit I plan to build are as follows:
The components values are:
R1 10k
R2 470k
R3 1M
R4 100k/1W
R5 47k
R6 1M
R7 56k
R8 adjustable 100k
R9 2.7k
C1 100nF
C2 10µF/35V
C3 100nF
C4 100nF
D1 30V Z-Diode
D2 1N4148
D3 1N4148
Q1 BC546

When this is done, I will post a film as well.

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