Reset Circuit - Olivetti ECR 7900 Service Manual

3-4. RESET CIRCUIT

The reset circuit prevents the CPU from starting to operate before the system is fully powered-up
and initialized. Then 29m sec. after power is applied, reset goes high and the CPU can begin
functioning.
When power is first applied to the circuit, the VBB begins charging C141 a capacitor.
Output of Reset IC(U10) is low-resistance at VBB-Line is less than 3.0 Volts.
VBB
U1 0
1
VOUT
2
VDD
3
GND
C2 9
BD5230G -TR
0.1 uF
Trouble shooting
- When power ON but no display / any key operation unable.
Check the voltage at point (1)
DC +3.3V - - - Reset circuit is OK. The problem may come from other causes.
0V - - - Reset circuit has a problem. Replace Main board.
Y108540-8
TP 11
RS T
5
C.T.
4
N.C.
C1 41
470 0pF
RE SET
Check the Power supply circuit again and replace Main board
if no problem found in the power supply circuit.
ECR 7900 Service Manual
VBB
R1 07
4.7 K
RE SET#
(1)
RESET#
27