New Hp9100A owner needs some repair help..

[trevor]

Stating your experience with electronic circuit repair helps us to
guide you...

To determine if the problem is in the Display or in the Logic:

See if there is any hint of green glow from CRT in dark room.
Turn on power, wait a minute, then turn off. Any green light
from CRT?

A common Display failure is the HV transistor Q1 and/or CR1,
see the Service Manual. Also the output transistors in the
Horizontal and Vertical boards. Before removing these two boards,
be sure to disconnect the four leads that go between the boards and
the CRT neck. The leads must be gently pulled off the radial CRT
deflection plate pins.


If the logic circuit is OK, pressing clear, clear, 1, change sign, square root,
should make the error light illuminate. Note however, the error light is
an incandescent bulb, so check that the bulb is OK.



Carefully unplug each of the five circuit boards and clean the gold edge
connector fingers with an Isopropyl Alcohol saturated paper towel.
Do not use abrasives. Carefully reinstall.


Consider removing the Card Reader temporarily....the Calculator will work
without it.

Trevor