HP 83522A Service Notes page 259

Model 83522A Service
a. If these are faulty, check the outputs of the latches, and replace them if
necessary. If the bit patterns are correct, but the waveforms are not,
replace the appropriate DAC.
-lOV REF
Check TP3 for -10 Vdc +1 mV. If this voltage is incorrect, perform the -lOV
Reference adjustment procedure provided in Section V of this manual. If the
adjustment cannot be made, check U23 pin 2 for -6.95 Vdc f 0.15 mV. If this
voltage is incorrect, replace U23. Check U20 pins 2 and 3 for -6.95 Vdc k0.15
mV. If either measurement is incorrect, troubleshoot U20 and associated
circuitry.
5V Regulator
Check A9Q3 pin 1 for slightly over +5 Vdc, and trace the line back to the 8350A
if the voltage is missing. Remove A7, A8, and RF ribbon cable W16 to check for
the possibility of excess loading. Then check A9Q3 pin 2 for +5 Vdc. If
incorrect, replace A9Q3.
CW Filter
Relay IS1 and C14 reduce residual FM by filtering the noise from the YO Coil
current. The relay is actuated by a line from U22. To check the data line, press
8350A
CW .
Enter:
SHIFT 0
0
2 GWzs
8 3
M2
0 0
1 BKSP
BKSP
Enters Hex Data command
Address location 2C83 (U22)
Hex Data Write
Enters hex data 00 and FF
Alternate between 00 and FF. Check U22, pin 6. If it is dead, make sure
protection diode CR5 is good. Then replace U22.
If U22 is working, alternate between 00 and FF, as described above, and verify
that contacts in relay K1 are opening and closing.