HP 3478A Technical Manual page 94

3478A
c. If both + 10V and -10V voltages are good and
the buffered + 10V is is low, lift jumper JM201 (see
Schematic 1). If the + 10V is now good, replace U102. If
still wrong, continue with the next step.
d. If the buffered + 10V is wrong or noisy, do the
following:
1. Check for a quiet -10V at pin 2 of U402.
2. If the voltage is wrong, replace U403.
3. If the voltage is good, connect pin 19 to pin 24 of
U403.
4. If the voltage at pin 6 of U402 is now at + 10V,
replace U403. If not, replace U402.
7-E-2
TM 11-6625-3071-14