Checking The Keyboard; Isolating Circuits - Wyse WY-60 Maintenance Manual

5. With the other lead from the DMM, look for the following
voltages at the specified points on the terminal PCB:
Voltage
+5V
~5%
+12V
~5%
-12V
~5%
Point
U1-40 (U1-20 is ground)
U27-14 (U27-7
is ground)
U27-1 (U27-7
is ground)
6.
If one or more of these voltages are not in tolerance,
adjust
VR101.
7.
If you adjust
VR101,
and the voltage or voltages are still
not within tolerance, replace or troubleshoot the terminal
PCB.
Checking the Keyboard
If you suspect the keyboard is the source of the problem, follow
this procedure to verify it:
1. Turn the terminal off.
2. Disconnect the communication cable.
3.
Connect pins 2 and
3
on the MODEM port.
4. Turn the terminal on.
5. The terminal should be in FDX (full-duplex) mode. (If it
isn't, go into setup mode, select the FDX parameter, then
leave setup mode.)
6. Type on the keys. Test all the keys in shifted and
unshifted positions. If the keys don't respond, see section
E of "Troubleshooting Flowchart."
Isolating Circuits
If you troubleshoot to the component level using the schematics
in Chapter 7, you may want to isolate the logic, monitor, or
power supply circuitry. Table
3-6
is a list of jumpers on the
terminal PCB and the areas they isolate. For an exact location,
see the terminal PCB component layout in Chapter 5.
3-15