The actual untouched grab of the BD665 Monoscope camera's output.

We have a number of monoscope tubes, three of them work to some extent. I have a nice test card C tube with ITV as a logo. It has good emission but it has some intermittent connection in the tube base. I have reflowed the pins with no improvement and I am reluctant to remove the base in case the intermittency is at the glass pinch. It's picture is good except for some spots that may be due to some contamination fallen on the target or possibly a scan collapse burn? Like camera tubes these should always be target upwards. There is also some unexplained shading in the central area. It is thought that this might be Helium gas poisoning. This comes about as the helium in the atmosphere sees the glass tube walls as an easy porous route to the attractive vacuum within! I also have a BBC test card C, but worryingly the getter is going white, and a test card G tube. All of them display the central shading or darkening with some dirt spots. The pictures shown are untouched screen grabs of the Monoscope camera's output. Once warmed up the Monoscope camera is quite stable in operation.

This tube was donated by Malcolm Beeson

Cathodeon Monicon Brochure

RCA 2F21 monoscope tube data sheet 1946

RCA 2F21 monoscope tube data sheet 1954
Restoration article

Copyright is retained in this electronic grab, but not of the test card design.