The PSU output is carried by a special
connector (pins 1 to 16) which mates with a socket in the CNY-2
case. The unit is designed to work from either a mains supply
100/110/220/230/240/250 volt or from a 12 volt or 24 volt battery.
Selection of the desired input is made by setting a 10-pin plug
into either an "AC" or "DC" socket mounted
on the top of the mains transformer (see below). Apart from the
plug/socket and DC voltage setting a specific set of fuses must
be fitted into a selection of holders and in addition the correct
4-pin vibrator, in this example for 24 volt operation, type NS/24
is fitted behind the front panel. HT is derived from a pair of
selenium rectifiers connected as a full wave bridge, 4.5H choke
L1, 8uF reservoir condensers C12/C13 and 8uF smoothing condensers
C14/C15. There's a switch for selection low or full HT (this
is primarily for enabling a reduction in battery drain and changes
the level between 175 and 250 volts).
The valves in the CNY2 equipment use
6.3 volt heaters so its easy enough to wire pairs of these in
series to run from 12 volts but not so easy to run from 24 volts
so this is accomplished rather inefficiently by using ballast
An 8-way switch on the power supply
front panel permits checking the state of the CNY-2 as indicated
on the label.