HP 721A Operating And Servicing Manual page 16

Sect. IV Page 4
Model 721A
($) MODEL 200CD
AUDIO OSCILLATOR
5 CPS-600KC
ADJUST OUTPUT TO MAIN¬
TAIN 10 VOLTS DROP (10 MA)
ACROSS 1000 OHM RESISTOR.
1*1.
E*>
CAUTtOH:
I AC
.010 Observe polarity
to prevent blocking
capacitor failure.
Figure 4-3 Measuring AC Infernal Impedance