Heathkit O-12 Lab Oscilloscope

[Bill Evans]

I just inherited a fairly dingy O-12 of unknown condition
and without a manual.  One tube is missing from its socket -
that being the only tibe in the unit that is NOT located on
a PC board.  It is located beside the main transformer and
the largest can electrolytic capacitor to the rear of the
horizontal portion of the chassis.

Before I spring for a manual, I'd love to find out what tube
is required, insert same and see what happens.  Can anyone
tell me what the tube type is that is missing?

Assistance will be much appreciated.

Bill Evans, VE4UD
313 Carpathia Road
WINNIPEG, Manitoba, Canada
R3N 1T2
PH:   (204) 489-7434
FAX:  (204) 487-7199
E-MAIL: bevans at ebsys.mb.ca
Company Web Site:  http://www.ebsys.mb.ca