GW Instek GDM-8245 - Power-On Test; Power Supply Checks

GDM-8245 Service Manual
40
Power-On Test
When switched on, the GDM-8245 will beep and then
perform a display test by lighting up every LED on the front
panel for around two seconds. By observing this power-on
test, service personnel can easily tell if there is any display
defect or problems in the power-on process.
Power Supply Checks
Symptom
Power supply related problems can be checked out by
referring to the power supply circuitry section, figure 2
(power supply block diagram) in the ―Theory of operation‖.
The steps in the table below can be used to narrow down
any power supply related problems.
Table 1
Step
Item
Expected Conditions
Comments
1
Line fuse
Check continuity.
Remove to check.
2
Line voltage
100V/120V/230V as
required.
Check fuse cover is aligned
with the correct voltage. See
page 80.
3
Line power
Plugged into live
receptacle, power on.
4
U102 input (Pin 1)
+18VDC
Referenced to U102 (Pin2)
5
U105 input (Pin 2)
-18VDC
Referenced to U105 (Pin1)
6
TP10
+15VDC
Referenced to U102 (Pin2)
7
TP11
-15VDC
Referenced to U102 (Pin2)
8
TP12
+3.1VDC
Referenced to U102 (Pin2)
9
Emitter of Q102
-3.1VDC
Referenced to U102 (Pin2)
10
TP14
+1.8VDC
Referenced to U102 (Pin2)
11
Pin 3 of U104
+1.8VDC
Referenced to U102 (Pin2)