BACK TO DIAGNOSTICS
a. Spill
The simplest way to confirm this diagnostic
is to get the customer to ‘fess up. If you’re
reluctant to make an accusation, look closely at the side edges of the cap
base. Most
spills seep in along the edge. Carefully lift the black rubber membrane
to expose the
traces for discoloration or other evidence of spill residue. If you can’t
see it, smell it
(gross, but effective). Inspect the bottom of the base plate. Spills often
seep through the
plastic welds or along the bottom edge.
b. Open language ID lines
The language ID lines are the rightmost
7 lines on the sense (right) connector. For US,
Australian and New Zeland keyboards, these should all be shorted together.
Foreign
language keyboards have conspicuous holes punched through some of these
lines. Test
for continuity (20 ohms or so is ok). An open language ID line won’t
necessarily
generate an error code. If it happens to be a valid language ID combination,
your
symptoms may be malselection, light impression or escapement failure. A
common
oversight is language mode. OK, so everybody knows this right? Well, everybody
had to
learn it the first time. Check the led array or display for language mode
indication. Hold
code and press X or L (depending on model, if unsure, no harm in trying
both).
c. SAPI switch
The semi-automatic-paper-insertion (why
don’t they just say paper feed?) switch is
interpreted by the electronics as a keystroke. If the switch housing is
cracked, machine
vibrations can send erroneous signals. This can result in intermittent,
erratic, undefinable
chaos that appears to be a keyboard malfunction. Disconnect SAPI. If it
goes away,
replace it. Good rule of thumb: if it’s wierd--pull SAPI. Although
it may defy your
diagnostic instincts, it takes only a second and makes you look more busy
than baffled
when the customer is peering over your shoulder.
d. Conductive debris on circuit board
Just a final check to ensure accurate
diagnostics. Paper clips, staples, etc. can generate
all manner of malfunction. Worse, they can destroy a good replacement part.
Specific to
keyboards, burned, melted lines are a solid indication of conductive debris.
When we
observe this condition, we will call to inform you. The keyboard is already
toast, but
let’s not fry another one.
Attempts to repair typewriter keyboards may cause further damage.
Plesase call tech support before proceeding.