Panasonic NE-1252, Service Manual

Page: 13 / 36

13
7.1.4. Diode
1. Isolate the diode from the circuit by disconnecting the
leads.
2. With the ohmmeter set on the highest resistance scale,
measure the resistance across the diode terminals.
Reverse the meter leads and again observe the resis-
tance reading. Meter with 6V, 9V or higher voltage batter-
ies should be used to check the front-to-back resistance
of the diode, otherwise an infinite resistance may be read
in both directions.
A normal diode's resistance will be infinite in one direction
and several hundred k
Ω
in the other direction.
7.1.5. Membrane key board (Membrane
switch assembly)
Check continuity between switch terminals, by tapping an
appropriate pad on the key board. The contacts assignment of
the respective pads on the key board is as shown in digital pro-
grammer circuit.
7.1.6. Temp sensor (Thermal protector)
A temp sensor is mounted on exhaust guide. Its purpose is to
automatically shut off the oven in case the cavity overheats for
any reason.
The thermal protector will operate at 257
°
F (125
°
C).
The device is connected to the DPC on touch control models.
When the thermal protector exceeds its temperature it will turn
off the power to oven cavity and display will go to reset mode.
The cooking program can be reset after cool-down.
THERMISTOR RESISTANCE VALUE
30K-120K at 10
°
C-30
°
C (50
°
F-86
°
F)