LG 42PW350 - Soft Touch Key Pad Resistance and Diode Mode Checks

Soft Touch Key
Pad Resistance
dd d
P100 (Key 1, Key 2) Resistance Reading with Soft Touch Key pressed.
KEY
Pin 3 measured
from Gnd
KEY
Pin 4 measured
from Gnd
an
d
Dio
d
e Mo
d
e
Checks
Power 3.0M Ohms Enter 3.0M Ohms
CH (Dn) 1.9M Ohms Menu 1.9M Ohms
Input 900K Ohms Volume (+) 900K Ohms
The Front IR Board
hKbd
CH (Up) 205K Ohms Volume (-) 205K Ohms
P100 Voltage Measurements with Soft Touch Key pressed.
KEY
Pin 3 measured
from Gnd
KEY
Pin 4 measured
from Gnd
h
as a
K
ey
b
oar
d
decoder that is
generating these
Resistance changes
when a Soft Touch Key
is touched
from
Gnd
from
Gnd
Power 2.4V Enter 2.42V
CH (Dn) 1.6V Menu 1.6V
Input
0.9V
Volume (
+
)
0.89V
is
touched
.
This in turn pulls down
the Key 1 and Key 2
lines to be interpreted
by the Microprocessor.
P100 Connector “FT IR Board“ to P902 “Main” (No Key Pressed)
Diode Mode
Input
0.9V
Volume
()
0.89V
CH (Up) 0.2V Volume (-) 0.2V
Pin Label STBY Run Diode Mode
3 KEY 1 3.29V 3.29V 2.58V
4 KEY 2 3.29V 3.29V 1.58V
Readings taken with
all connectors
Disconnected. Black
lead on Gnd. DVM
in Diode Mode.
June 2011 42PW350 Plasma
158