Panasonic KX-FT21BX - Page 93

TROUBLESHOOTING GUIDE
- 67 -
KX-FT21LA
X3=24MHz
AC POWER ON
+5 V: Is there +5 V at pin 7 of CN1?
+3.3 V: Is there +3.3 V at Q2 CORRECTOR?
Problem with the power supply
unit.
Check Q2, Q3 and Q1.
NG
NG
Check the reset signal line
and reset IC (IC4).
*Check IC1 (ASIC) 82 pin = 6MHz.
Check the status by test types
A, B, C and D. See page 68.
See page 69.
See page 70.
NG
OK
OK
[1] Power check
[2] Oscillation
[3] Reset
[4] Check each signal line.
Reset: IC1 (ASIC) 14 pin
5V
0V
4mS
D0~D7
A0~A16
RD
ROMCS
WR
RAMCS
A
A
B
C
Constant 5V
C
Constant 5V
Constant 0V
B
Constant 0V
WDERR
A
WDERR
Use this
order.
1
2
3
After the power is turned on, the ASIC(CPU) initializes and checks each IC.
The ROM, SRAM, and Modem are checked.
If initialization fails for the ICs, the system will not boot up.