Printronix L1024, Maintenance Manual

Page: 206 / 372

10–8 Chapter 10 – Control Panel
If you observe any of these symptoms, replace the entire display panel, since there are no replaceable
parts in it.
1. Missing row of pixels. The quickest way to check whether the panel is good or not is by
substitution. If the problem disappears when you replace the panel, the old panel was bad
and no further work is required. If, however, the panel is still missing pixels, perform a
continuity check of the 26-pin cable that goes to the data controller. Begin by removing the
bottom cover of the printer. The panel cable is a one-to-one type that plugs into the
Backplane Board at J3. The pinout of the cable is shown in Table 10–1 on page 10–3. If both
the panel and the cable check out OK, replace the data controller.
2. Keys not operating properly. The seven keys on the panel have a decal attached to the
plastic housing that makes up the bulk of the display panel. The key coverings, in turn, press
against seven small switches that are on the LCD printed circuit board. Two of the probable
failure modes for the keys are:
S
The key covering is not making contact with the switch underneath it, or
S
The switch itself is bad.
Check these possibilities as follows:
a. Turn the printer off and remove the display panel.
b. Locate the pin on connector CN for the suspected bad key.
See Figure 10–2.
c. Place one lead of an ohmmeter on pin 2 (ground) of CN and the other lead on the pin of
the suspected bad key. Try pressing the key and see if the reading goes from open to
closed. If not, then replace the display panel.
d. If the ohmmeter reading
does cycle from open to closed, then check the wiring harness,
the backplane board, and the data controller board.