Microprocessor Troubleshooting - ELCOM Euro-500 Handy Series Service Manual

Euro-500TX Handy
• ECR doesn't function (external power supply disconnected)
damaged or disconnected main power switch
damaged cable between the main PCB and Intercon PCB
blown SMD fuse F2
flat accumulator
incorrect VCC voltage value
incorrect VRAM voltage value
• RAM is erased every time the ECR is turned on
damaged backup NiCd accumulator
wrong position of JP1 jumper
• the "Head overheat" appears after the ECR is turned on
VCC1 power supply malfunctions
• the ECR doesn't print (step-motor feeds the tapes)
VH power supply malfunctions
• the ECR reports a FM error
some FM power supply circuits malfunction – check the output voltage of the secondary power

6.2 Microprocessor troubleshooting

• the ECR doesn't react after it was turned on, displays garbled characters, prints undefined characters,
beeps, or flashes the LCD backlights
60
Service manual
– check the switch cable connection into the main PCB
(PWRSW connector)
– check the switch functionality using the multi-meter
(look at the keyboard PCB)
– check the integrity of the 2-wire cable that connects
the connector PCB to main PCB using the multi-me-
ter
– check the proper plugging of the connector cable into
the main PBC (REAR2 connector)
– check the SMD fuse F2 (1.85 A) – replace
– check accumulator voltage, if it is low – charge the
accumulator, if accumulator loses voltage quickly or
cannot be charged – replace it
– check the connectors BATT1 and BATT2
– check the Charger circuit charging voltage
– check whether the NMI reaches the 4.5 V value after
the main power switch is turned on, depending on the
accumulator (if not, check U12, R5, R6, C13)
– if NMI signal is correct replace U14
– check whether the VCC power supply is not short-
circuited toward GND (damaged semiconductive
part)
– damaged D4 diode – replace
– check whether the VRAM power supply is not short-
circuited toward GND (damaged semiconductive
part)
– replace it only with accumulator of identical type
– the correct position is farther from the NiCd accumu-
lator (the position nearer NiCd erases the RAM)
– use the oscilloscope to determine if SAVEPWR and
NMI signals reach log. 1 at ECR start, if they do,
measure or replace R29, R35, R113, T5 – T7 (during
test #910)
– use the oscilloscope to determine if SAVEPWR and
NMI signals reach log. 1 at ECR start, if they do,
measure or replace R1 – R4, T1 – T3 (during test
#910)
– check the VHSU signal (24 V)
– check, event. replace, the Step-up converter parts
supply (use test #730), event. replace U15
– check the output voltages of the FM power supply
circuits (event. replace T8 – T10, U16, D6 – D8, D18,
R14 – R19)
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