Tektronix TLA 714, Service Manual

Page: 107 / 159

Troubleshooting
4–60
TLA 714 Color Portable Mainframe Service Manual
Bypassing Front Panel Controls
The front panel control assembly can be bypassed if necessary to assist in
troubleshooting. Bypassing the front panel control assembly allows an external
keyboard and mouse to function bypass the front panel control board as in a
standard PC.
To bypass the front panel control assembly, unplug the cable from it to the front
panel interface board (located behind the flat-panel display) at J102. Then, use
jumpers to connect pins 33 and 34, pins 31 and 32, pins 27 and 28, and pins 25
and 26. See Figure 4–27.
J102
Figure 4–27: Jumper locations for bypassing front panel control assembly
Checking the Power Supply Voltages
Power off the mainframe and remove any modules installed in it. Power on the
portable mainframe and connect the reference lead of a digital voltmeter to
chassis ground, such as the top of the power supply.
Attach a 0.025 inch square pin to the probe tip of the other lead and insert it into
a pin on one of the backplane connectors. The pins that should be carrying
voltages are listed in Table 4–4.
The arrangement of J1 and J2 connectors on the backplane is shown in Fig-
ure 4–28 on page 4–62.
Measure the power supply voltages with the voltmeter and compare each reading
to the values listed in the tables. If the voltages are within about 5% of the
nominal voltages, your power supply is functional.