HP 83522A Service Notes page 236

Service
Model 83522A
Initiate the check as follows
SMfFT
O
0
Hex Data mode
2 BKSP
O
O
Address location 2F00 (U8)
kz.$ Hex Data Rotation Write
Check L FP5 line for activity. Check data lines for patterns illustrated in Figure
8-2.
To check the RF ON relay, K1, make the same key entries as above, except enter
M2
for Hex Data Write. Then alternate between data inputs: O 6 and
BKSP
BKSP
(FF). The RF ON line should toggle from 0 Vdc to -10 Vdc. If
there is no change, check U8, pin 12, for high and low levels. If the output is
locked high, check the protection diode, CR3, before replacing U8. However, if
CR3 is open, U8 may be damaged by actuating the relay. If the output at pin 12
is locked low, replace U8. If U8 pin 12 changes levels properly, replace relay K1.
Miscellaneous
The FREQ CAL and EXTIMTR ALC CAL offsets are generated by A1
potentiometers, with the wipers running between + l o Vdc and -10 Vdc. If the
signals are absent, check for the +10V and -lOV supplies. If the offset voltages
still cannot be produced, replace the defective potentiometer, R3 or R4.