User Guide

PAMS
Technical Documentation
RAE-3
8. Troubleshooting
Page 8 – 100
Issue 1 06/01
3.4 Backlight troubleshooting
NOTE: when making measurements, make sure that BACK_PWM is 100%
Measure
DRAIN
Check V152
and R158
Measure
VCO_OUT
Measure
FEEDBACK
OK?
Check VCO
components:
R174, V156,
C173, C172,
N153, R175,
R179, R178,
R177, R176,
D155 and
R160
Other frequency
95–110 kHz
No signal
150–180kHz
Still fails
Check components:
D150, D151, R156,
R150, ,
R157, R169, V150,
V151, and L150
R172, R151
Between 95kHz and 180kHz
Else
Measure
PIEZO_IN
No signal
Square wave
Check L151
Check lamp
and R158
Check PIEZO
and X006
Feed 1.2VDC
to VCO_IN.
Now frequency
of DRAIN should
be 135kHz
95–110 kHz
No
Yes
Measure
SIGN
OK?
No
Yes
Check components:
C154, R165, R166,
R153, R171,R164,
R180, R170, R163,
N152, D152, R173,
C169, R152, V155
Check components:
N151, R154, C170,
R161, R162, N152,
R159, D154, R155,
C153, V152, R168
No PDA
backlight
Figure 100.