Panasonic KX-FT21BX Service Manual page 94

KX-FT21LA
Put the unit in the test mode and check the voltage at lands A, B, C and D.
(TEST LAND)
IC2
D C
A
B
IC7
IC1
Turn off the power supply.
Short using a metallic object, such as tweezers, between the test and GND land, and turn on the AC power.
Check the following voltages by using an oscilloscope or tester.
To cancel the status check mode, turn off the AC power.
Check point voltage
Item
A
CLOCK(IC1) 5V
MODEM(IC1) 0V
S-RAM(IC3) 0V
ASIC(IC1) 0V
ALL OK 5V
This indicates that the Add/Data Bus, RAM, ROM,
MODEM, and ASIC are all completely
connected to the CPU and that control from
the CPU is possible.
Tester
TEST
GND
B C D
0V 0V 0V IC1
5V 0V 0V IC1
0V 5V 0V IC3 (20 pin), IC1 (6 pin), IC3
0V 0V 5V RA1~RA4, R10,12, IC1 (104~136 pins)
5V 0V 0V
Please check the soldering and conduction of these
components.
If there is no problem, replace the lCs.
If you still have a problem with the digital board, please see
"checking details". (Refer to page 62.)
To cancel the status check mode, turn off the AC power.
GND
Check points
- 68 -
AC