HP 212A - Thyratron Replacement

Power Supply Adjustment -- The D. C. output voltage of the regulator is
adjusted by varying the grid bias of the amplifier tube with a potentiom-
eter.
Following service to the power supplies, three checks must be
made as follows:
1.
Check voltage between the cathode (pin 6) of V17 and ground.
If necessary, adjust R33 to obtain 300 volts.
2.
Check voltage between the center terminal of RllO and ground.
If necessary, with instrument not pulsing, adjust RL 10 to obtain
-28 volts at the center terminal.
3. Check maximum output pulse amplitude. If necessary, adjust
R35 to obtain 60 volt pulse amplitude.
Relay Adjustment -- (Normally not required for life of relay)
1.
Open circuit between relay and RZ8.
2.
Insert milliarnmeter between relay and pin 5 of V17,
3.
Set pulse rate dial at max. and sync selector to X1Q.
4.
Control current through relay by varying R124.
Set relay to ac -
tuate at 50 ma by adjusting tension on armature springs,
5.
Reconnect R28 to relay and reset pulse calibration.
4-3 SERVICING NEGATIVE HIGH VOLTAGE SUPPLY (V4, V12, V14, Etc. )
Following replacement of parts within the negative high voltage supply
the current through the voltage regulator tube V4 should be measured
at line voltages of 105 and 125 volts.
If necessary, th8 value of R1
may be padded to obtain not less than 10 rnilli-amperes with a line
voltage of 105 volts and not more than 30 milli-amperes with a line
voltage of 125 volts.
4-4 THYRATRON REPLACEMENT
V6 and V16 are critical tube positions.
To quickly check a thyra-
tron suspected of being faulty interchange V6 and V 16 to see if the
observed symptoms change as the tubes are exchanged,
For ex-
ample, if jitter 39 observed on the trailing edge of the pulse, but
not on the leading edge, exchange V6 and Vl6.
If jitter now appears
on the leading edge and not on the trailing edge as it did before, the
trouble is clearly a result of the thyratron now in the V6 position,
However,
if the jitter remains on the trailing edge in spite of the
tube change, the trouble is most likely in the circuits as sociated