HP 120A - Page 29

Sect, n Page 13
CONNECTION TO DEFLECTION PLATES
VERT. HORIZ.
CAUTION - Deflection plates of cathode-ray tube operate at high de potentials. TURN 120A OFF
BEFORE REMOVING COVER PLATE FROM DEFLECTION PLATE TERMINALS.
To connect an external signal to the deflection plates:
A. AC COUPLED
1. Remove the jumpers going to terminals DI
and D2 for horizontal input and/or D3 and
D4 for vertical input.
2. Connect 1 megohm 1/2 watt resistors in place
of the jumpers removed in step 1.
3. Connect the vertical input blocking condensers
to terminals D3 and D4 and the horizontal in 
put blocking condensers to D3 and D4.
The POSITION controls on the 120A will still con 
trol the pattern and good focus will be maintained.
B. DIRECT COUPLED
1. Remove the jumpers going to terminals DI
and D2 for horizontal input and/or D3 and
D4 for vertical input.
2. Connect leads from the vertical input directly
to D3 and D4 and the lead from the horizontal
input directly to Dl and D2.
POSITION controls will no longer control pattern.
Position voltages must be furnished by the signal
source. Best picture focus is obtained when
plates are at +275V with respect to 120A chassis.
Figures 2-11