Panasonic NE-1252 User manual

© Panasonic Corporation 2012 Unauthorized copy-
ing and distribution is a violation of law.
Order Number MOD1206355CE
Commercial Microwave Oven
Model No. NE-1252
Model No. NE-1752
Model No. NE-1772
Model No. NE-2152
Model No. NE-12521
Model No. NE-12523
Model No. NE-17521
Model No. NE-17523
Model No. NE-17723
Model No. NE-21521
Model No. NE-21523
TABLE OF CONTENTS
PAGE PAGE
1 Safety Precautions----------------------------------------------- 2
2 Specifications ----------------------------------------------------- 3
3 Technical Descriptions ----------------------------------------- 4
4 Location of Controls and Components ------------------- 5
5 Installation Instructions ---------------------------------------- 6
6 Operating Instructions------------------------------------------ 7
7 Test Mode ----------------------------------------------------------12
8 Troubleshooting Guide --------------------------------------- 14
9 Disassembly and Assembly Instructions--------------- 17
10 Measurements and Adjustments -------------------------- 22
11 Schematic Diagram -------------------------------------------- 25
12 Exploded View and Replacement Parts List ----------- 29

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1 Safety Precautions

3
2 Specifications
Models: NE-12521
NE-12523
NE-1252 NE-17521
NE-17523
NE-17723
NE-1752
NE-1772
NE-21521
NE-21523
NE-2152
Power Source: 120 V AC Single Phase 60 Hz 208/230 V AC Single Phase 60 Hz
Power Requirement: 1990 W, (17.3A) 1970 W, (17.1A) 2650 W, (13.6A)
208 V
2610 W, (13.5A)
208 V
3160 W, (16.3A)
208 V
3120 W, (16.1A)
208 V
2650 W, (12.2A)
230 V
2610 W, (12.2A)
230 V
3160 W, (14.9A)
230 V
3120 W, (14.7A)
230 V
*High
frequency
Output:
HIGH (P10) 1200 W 1700 W 2100 W
MED (P5, P4) Approx. 55%~45% Approx. 55%~45% Approx. 55%~45%
DEFROST (P1) 340 W 340 W 340 W
Microwave Frequency: 2,450MHZ
Timer: Maximum programmable time for single stage heating
P10-P2 power = 15 min.
P1 (DEF) = 30 min.
Outside Dimensions: 16 5/8 inch (W) X 20 inch (D) X 13 1/4 inch (H)
422 mm (W) X 508 mm (D) X 337 mm (H)
Inside Dimensions: 13 inch (W) X 12 7/32 inch (D) X 6 7/8 inch (H)
330 mm (W) X 310 mm (D) X 175 mm (H)
Weight: 56 lbs/25.5 kg 60 lbs/27.5 kg 66 lbs/29.5 kg
*Output power: IEC705-88 Test procedure
Specifications subject to change without notice.

4
3 Technical Descriptions
3.1. Description of operating sequence
Variable power cooking control
The coil of power relays are energized intermittently by the digital programmer circuit, when the oven is set to MEDIUM or
DEFROST power position. The digital programmer circuit controls the ON-OFF time of each power relay contacts in order to
vary the output power of the microwave oven. One complete ON and OFF cycle of the power relay is 44 seconds. The relation
between indications on the control panel and the output power of the microwave oven is as shown in Figure.

5
4 Location of Controls and Components
4.1. Outline diagram

6
5 Installation Instructions
5.1. Wiring requirements and power source voltage selection
Wiring Requirements
No other appliance should share the circuit with the micro-
wave oven. If it does, the branch circuit fuse may overload
and either cause the oven to heat slower than expected or
blow the fuse.
1. For Mode NE-12521/NE-12523/NE-1252
The oven must be on a SEPARATE, 20 Amp, 60 Hz-120V
GROUNDED CIRCUIT.
2. For Model NE-1752/NE-1772/NE-17521/NE-17523/NE-
17723
This oven must be on a separate, 60 Hz GROUNDED
CIRCUIT-minimum 15 amps.
3. For Model NE-21521/NE-21523/NE-2152
This oven must be on a separate, 60 Hz GROUNDED
CIRCUIT-minimum 20 amps.
Power Source Voltage Adjustment
For 208V/230V models
The microwave oven automatically detects 208 V and 230
V-240 V. Insert the plug, and if the Digital Display Window
goes blank 10 seconds after use, unplug and insert the plug
again.

7
6 Operating Instructions
6.1. Operation procedure
1. Manual heating for single stage 2. Manual heating for 2nd or 3rd stage
NOTE: For a 3rd stage heating cycle, select a further
power level and time between steps 3 and 4 above.

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3. Memory setting for single stage
TO PROGRAM MEMORY AREA B: Follow steps 1 above.
Touch the Memory Shift pad twice and a small [B] will
appear beneath the flashing [PROG].
Touch the memory pad you wish to program, and the previ-
ously selected time and power level will appear in the dis-
play window.
NOTE: Once the Memory area B has been selected it
cannot be changed back to Memory area A. If you do
not require Memory area B, cancel it by touching the
cancel pad and begin again.
4. Memory setting for 2nd or 3rd stage
NOTE: For a 3rd stage heating cycle, select a further
power level and dial in a time, between steps 3 and 4
above.

9
5. Memory pad heating
NOTE: When program is locked, heating can be started
automatically by tapping memory pad.
6. Programming Double or Treble Quantity Pad

10
7. Memory Pad Heating for Double or Treble Quantity Heat-
ing
8. To Read the Cycle Counter
NOTE: Total cumulative number includes programming
memory heating and manual heating number of times
has been used. Cooking times over 99,999 times will be
back 0.
9. To Activate Program Lock

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10. To Release Program Lock 11. To Select Beep Tone Options
To select length of tone at end of heating cycle there are 3
options.
1. 3 beeps (factory setting)
2. 60 seconds of short beeps.
3. Beep sounds for 5 seconds, and 3 beeps 30 seconds
later and 60 seconds later again.

12
7 Test Mode
7.1. Component test procedure
7.1.1. High voltage transformer
1. Remove connections from the transformer terminals and
check continuity.
2. Normal (cold) resistance readings should be as follows:
Secondary winding Approx. 80Ω-120Ω
Filament winding Approx. 0Ω
Primary winding Approx. 0Ω-3Ω
7.1.2. High voltage capacitor
1. Check continuity of capacitor with meter on highest OHM
scale.
2. A normal capacitor will show continuity for a short time,
and then indicate 9MΩonce the capacitor is charged.
3. A shorted capacitor will show continuous continuity.
4. An open capacitor will show constant 9MΩ.
5. Resistance between each terminal and chassis should be
infinite.
7.1.3. Magnetron
Continuity checks can only indicate an open filament or a
shorted magnetron. To diagnose for an open filament or
shorted magnetron.
1. Isolate magnetron from the circuit by disconnecting the
leads.
2. A continuity check across magnetron filament terminals
should indicate one ohm or less.
3. A continuity check between each filament terminal and
magnetron case should read open.

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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 kΩin 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)

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8 Troubleshooting Guide
8.1. Cautions to be observed when troubleshooting
Unlike many other appliances, the microwave oven is high-volt-
age, high-current equipment. Though it is free from danger in
ordinary use, extreme care should be taken during repair.
8.1.1. Check the grounding
Do not operate on a 2-wire extension cord. The microwave
oven is designed to be used in a completely grounded condi-
tion. It is imperative, therefore, to make sure it is properly
grounded before beginning repair work.
8.1.2. If the door lock, the door switch,
the door seal or the door develops
a malfunction, be sure not to oper-
ate the oven until complete repairs
are made.
If the oven is operated with any of these parts in imperfect con-
dition, hazardous microwave leakage might occur.
8.1.3. Warning about the electric charge
in the high voltage capacitor
For about 30 seconds after the oven is turned off, an electric
charge remains in the high voltage capacitor. When replacing
or checking parts, remove the power plug from the outlet, wait
30 seconds and short the terminal of the high voltage capacitor
(terminal of lead wire from diode) to chassis ground with an
insulated jumper lead wire or an insulated handle screwdriver
discharge.
8.1.4. When parts must be replaced,
always remove the power plug from
the outlet, and discharge the high
voltage capacitor.

15
8.1.5. Confirm after repair
1. After repair or replacement of parts, make sure that the
screws of the oven, etc. are neither loose nor missing.
Microwave might leak if screws are not properly tight-
ened.
2. Make sure that all electrical connections are tight before
inserting the plug into the wall outlet.
8.1.6. Avoid inserting nails, wire, etc.
through holes in unit during opera-
tion.
Never insert a wire, nail or any other metal object through the
lamp holes on the cavity or any other holes or gaps, because
such objects may work as an antenna and cause microwave
leakage.

16
8.2. Troubleshooting guide

17
9 Disassembly and Assembly Instructions
9.1. Replacement of magnetrons
(Upper and Lower)
Upper magnetron
1. Discharge electric charge remaining on the high voltage
capacitors.
2. Remove the entire rear panel by removing screws as
shown.
3. Disconnect all lead wires from magnetron and thermal
cutout.
4. Remove the 4 screws holding magnetron.
5. Remove 2 screws holding thermal cutout.
6. Remove the mounting bracket from magnetron and install
it on the new magnetron.
Lower magnetron
1. Discharge electric charge remaining on the high voltage
capacitors.
2. Remove the entire rear panel by removing screws as
shown.
3. Carefully place the unit on its left side (H. V. Capacitor
side).
4. Remove the cover by removing 2 screws.
5. Remove the 4 screws holding magnetron by inserting
screwdriver through the 4 openings on bottom plate.
6. Remove 2 screws holding thermal cutout.
7. Remove the mounting bracket from magnetron and install
it on the new magnetron.
NOTE: To prevent microwave leakage, tighten mounting
screws properly making sure there is no gap between the
waveguide and the magnetron.

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Removal of Positive Lock connector
The positive lock connector is a specially designed loose
free connector and you will find this connector in many lead
wire connections. To remove this connector, pull the lead
wire by pressing an extruded lever in the center of recepta-
cle terminal as shown.
9.2. Replacement of power relay
circuit board (PCB MU)
NOTE: Be sure to ground any static electric charge built up
on your body, before handling the power relay P. C. B..
1. Disconnect all lead wires from power relay circuit board.
2. Remove the power relay P. C. B. together with its mount-
ing bracket by first removing the 1 bracket holding screw.
3. The power supply P. C. B. can be separated from mount-
ing bracket by removing the 2 screws.
9.3. Replacement of digital pro-
grammer circuit board (PCB
AU)
1. Disconnect 2 flat cables from PCB A(U).
2. Disconnect all of the connector from PCB A(U).
3. Remove 2 screws holding PCB A(U) to detach it from its
mounting bracket.
NOTE1: Please use care in handling the D. P. C. board to
avoid damage.
NOTE2: After replacing the PCB AU with new one, set the
power voltage (208V or 230V) up as below procedure.
1. Open the door and leave it open.
2. While pressing START pad, close the door and open it
again.
3. Press SHIFT [A/B/C] key within 10 second after openning
the door.
4. Press X2 or X3 key to set the voltage up.
• When X2 key is selected, [208] will appear, and [230]
appears when X3 key is pressed.
5. Press PROG pad to set the voltage up.
• After 3 seconds, the power voltage selected will disap-
pear and 0 appears in the display window.
• It has been just completed.
9.4. Replacement of PCB BU (for
display tube) and membrane
switch
1. Remove the grounding screw for membrane switch.
2. Disconnect 2 flat cables of membrane switch and PCB
B(U) from PCB A(U).
3. Remove 3 screws holding control panel and detach it
from the unit.
4. Remove 2 screws to detach PCB B(U) from the control
panel.
5. Detach escutcheon A from escutcheon base by releasing
hooks, and also remove membrane switch from it.

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9.5. Replacement of upper antenna
1. Remove ceiling plate by gently moving the left and right
tabs inward while pulling the plate down and outward.
2. Using a small flat screwdriver or the like, remove two
plastic clips located on the antenna ring. Next turn the
antenna ring approx. 1/8 turn clockwise to unhook the
tabs and pull off.
9.6. Replacement of floor shelf and
lower antenna
1. To remove the floor shelf, insert a screwdriver through the
small opening on the left side of the oven cavity and care-
fully lift the floor shelf.
2. For removal of lower antenna, use the same procedure
as upper antenna.

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9.7. Replacement of temperature
sensor (Thermal protector)
1. Cut 2 lead wires at the top of sensor terminals.
2. Remove 2 screws holding temp sensor and replace with
new one.
3. Solder the lead wires securely to the sensor terminals.
9.8. Disassembly of door assembly
1. Remove each 2 bolts holding upper and lower hinges.
2. Open the door and while pulling the door outward, work
upper and lower hinges out through the holes of the front
surface of oven.
3. Remove door C (check cover) from door E by carefully
pulling outward starting from the upper right hand corner.
4. Remove 2 screws holding door handle and separate door
A from door E by carefully freeing catch hooks.
5. Remove door key, door key lever, door key spring and
handle pins from door E.
6. Assemble the door by taking the above steps in a reverse
order.
Replacement
1. When mounting the door to the oven be sure to adjust the
door parallel to the bottom line of the oven face plate by
moving the upper hinge and lower hinge in the direction
necessary for proper alignment.
2. Adjust so that the door has no play between the inner
door surface and oven front surface. If the door assembly
is not mounted properly, microwave may leak from the
clearance between the door and the oven.
NOTE: Please refer to [10.1. Measurements and adjust-
ments].