Update:
All the voltages are good according to service manual including +/- 10V including buffered +10V, and three voltages 3.3, 2.2 and 1.1V on the pin 1, 2, 3 of the W501 for display. I do have capacitor ESR meter and these 5 electrolytic capacitors checks out, and all the silver axial capacitors are not shorted.
This multimeter is early version (eg does not have CR520) and seems to test digital circuits using programmed routines based on SA1 or SA2 via dipswitch 6 or 7.
SA1 (dipswitch 6 on) displays this way: LCD display flashing dimly every approx 1 second, means 1.3 second watch dog triggering on failure to reset the U504 IC on pin 2, which did repeatedly bounce the reset circuit for microcontroller U501 IC pin 4 cyclically. Switch dip 6 off, stable with this reset circuit is held steadily high with display all lit up.
How this SA1 mode behaves make me to believe that display is not the issue,
Could be either digital section is jammed by other D/A, or latch IC or corrupt ROM IC. I don't have resources to program new ROM IC have to ask someone to send me one for HP 3468A.
How reliable are CD4076BE ICs are? These are part of digital bus and one of pin drives the watch dog counter. What about the SN74LS373N is these known to fail?
Thanks and cheers,