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NE-972
6. Humidity Sensor and digital programmer circuit
(Fig. 22) (For NE-992/NE-993 only)
CAUTION
Do not touch any parts of the circuitry on the digital
programmer
circuit since static electric discharge
may damage this control panel.
Always ground yourself while working on this panel to
discharge any static charge built up in your body.
(A) Check across sensor heater terminals. Normal cold resistance should
read approx. 6 ohm.
(B) In order to determine if the Auto Sensor function of the digital prog-
rammer circuit is in working order or not, do the following test.
1) Place a water load in the oven.
2) Unsolder 2 shieided wires connected to sensor terminals.
3) Tap Auto Sensor Cook Control Pad twice to set auto sensor cook-
ing at A4 and tap Start Pad.
4) About 10 seconds after Start Pad is touched, short shielded wires
for 5 seconds and then remove them. Before shorting the shielded
wires you can watch the sensor heater glow red.
5) The oven lamp will dim a little, about 60 seconds after the Start Pad
is tapped. This indicates that magnetron has started oscillation.
6) After approx. *10 seconds
(Ti TIME), short the shielded wires
again.
7) Category number
"4" stays on and following
digits (see chart)
should appear indicating **additional cooking time (T2 TIME).
The time should start to count down and oven should shut off when
the time has elapsed.
:
* T2 TIME
TI TIME
(Additional Cooking Time)
10 sec.~19 sec.
10 sec.
20 sec.~29 sec.
20 sec.
The Auto Sensor function in the digital programmer
circuit is
working in order if above condition is obtained.
7. Low voltage transformer
Check the voltage of secondary winding of the low voltage transfor-
mer (L.V.T.. The normal voltages of the L.V.T. with no load should read
as shown in Fig. 23A & 23B.
When measuring the voltage of L.V.T., measure the voltage between
each pin of the L.V.T. with the connector (CN1) unplugged.
CAUTION
A 240V AC is present at the primary circuit of the low
voltage transformer. When
checking the secondary
voltage of low voltage transformer,
be cautious of
possible shock hazard.
8. To test the oven temp sensor thermistor
This senso
monitors the heat produced
by the heater circuit and
maintains the oven temperature the user had selected norma! room
temperature, especially in a kitchen can vary anywhere from 10°C to
32°C. The reading across the oven sensor thermistor should be within
360K ohm to 800K ohm when read in an area within the 10°C to 32°C
room temperature range.
If the resistance reading is out of the range stated here, the sensor is
defective and must be replaced.
NOTE
1: When measuring resistance disconnect the 5-pin connector
(CN3) from the DPC otherwise a false reading may be indi-
cated.
NOTE 2: tf checking an oven sensor thermistor just after the microwave
oven has been operating, the sensor of course won't be room
temperature. In this case the sensor must be removed and
allowed to cool down to the 10°C to 32°C range.
GUARD RING
SENSOR HEATER TERMINALS
SENSOR TERMINALS
SHIELDED
WIRE
HUMIDITY SENSOR ELEMENT
Fig. 22
For NE-992/NE-993
PIN NO. OF LV.T
SECONDARY VOLTAGE
Si - $2
AC 14.7V + 10%
$3 - $4
AC 19.9V + 10%
S5 - S6
AC 3.58V + 10%
Primary voltage:-----AC 240V
Fig. 23A
For NE-972
PIN NO. OF L.V.T
SECONDARY VOLTAGE
Primary voltage------AC 240V
Fig. 23B
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