Multitone RPR750 Series, Руководство пользователя и сервисное руководство, Страница: 39 / 66

TM1215 Iss. 6.0
RPR750
3. Check that the reset line is high i.e. the supply rail is within limits and the micro-
processor is operational.
Fault condition found - check IC5 pin 1, or the junction of C16 & R19. If the reset line is
low, then the 3.3V line may be outside limits, IC 5 may be faulty, or there could be a short
circuit elsewhere on the line.
4. Check that the backup cell BATT2 is being charged. On BATT+ terminal, there should
be 3.3V ±10% (this may vary between 0V and 3.3V on a new decoder, as it may take up
to 24 hours for BATT2 to be fully charged).
Fault condition found - check R17, or BATT2.
5. Check that the micro-processor clock crystal is oscillating and the frequency is
4.194MHz ±0.01%.
Note - this measurement should be made within a few seconds of powering-on the
decoder, as once the initialisation sequence is complete, the decoder will start to use the
STOP mode and the main oscillator will be switched off for most of the time.
6. Check that the micro-processor sub-system oscillator (XL2) is running @ the correct
frequency, either 32.768kHz for 512 Baud or 38.4kHz for 1200 Baud rate receivers.
Note - this oscillator should run continuously.
4.5.5 Alpha-numeric Display does not work
Check for poor solder joints on R68 - R73, R76 & R81. Check for solder short circuits on
SK5. Change the Liquid Display Module (LCM) for a known good unit. If the display starts
to work, replace the faulty LCM.
4.5.6 Display Backlight does not work
Check that the backlight has not been software inhibited (battery low for example). If not,
measure the voltage on IC1 pin 20, or IC12 pin 39 for the MKII variant, (B/L); when the
light is active, this should be a 3V minimum pk-pk square wave, @ approximately 30kHz.
If the correct driving waveform is present on IC1 pin 22 (IC12 pin 41), check R79, TR9,
L2, or the backlight LED on the LCM module.
4.5.7 Decoder does not "Beep"
For test purposes, the Beep signal may be activated either during the switch-on
initialisation, or when the
mute
button is pressed to determine the pager status. First
check that the loudspeaker is connected and there are no shorts on SK4.The beep signal
should be measured on IC1 pin 21, or IC12 pin 40 and is typically a 2.7kHz square wave.
If the signal is not present, then there is a solder short, a fault in IC1/IC12, or the beep
output is inhibited in the software, as the result of an EEPROM option.
If the O/P from IC1/IC12 is present, measure the supply voltage to the audio amplifier (IC8
pin 10) and check that the amplifier is enabled (IC8 pin 2 = 0V). If not, fault lies with IC8,
or IC11.
4.5.8 Decoder Vibrate Motor does not operate
1). Check that the vibrate-motor signal O/P from IC1 pin 12 or IC12 pin 57 is @ 3V, when
the motor should be active. 2). Check that TR3, R16 and TR2 are functioning correctly.
3). Check the vibrate motor itself is working.
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