Panasonic Automatic Rice Cooker Sr Ga721 Srga281 Srga421 Operating Instructions

							
Service Manual
Order No. PHAT070510C3
Automatic Rice Cooker
SR-GA421/SR-GA281/SR-GA721
EXPORT
©  2007  Panasonic  Home  Appliance  (Thailand)  Co.,Ltd 
All  rights  reserved.  Unauthorized  copying  and  distrbution  
is a violation of law. 
Specification 
Specification subject to change without notice. 
ModelSR-GA421SR-GA281SR-GA721Detail
CountryHKSIN-DBDSIN-RBDMALAYSIAHKMALAYSIASIN-DBDSIN-RBDUSA
Power Source220 V / 50 Hz 230 V / 50 Hz220 V / 50 Hz240 V / 50 Hz220 V / 50 Hz240 V / 50 Hz230 V / 50 Hz 220 V / 50 Hz208 V / 60 Hz
Powerconsumption 
Cooking1400 W950 W2500 W
Warming
47.5 W
Cooking capacity5 ~ 23 L5 ~ 15 L3 ~ 7 L
Center thermostatworking temperature140 °C
Keep warm temperature More than equal to 80 °C (After 1 Hr. keep warm)
Thermal fuse specification 113  
169 °C
Dimension (mm)Width x Depth x Height 429 x 369 x 300367x 295x 305248 x 247 x 255
Weight
5.5 kg3.6 kg10.1 kg
Power Cord (approx.)1.0 m
AccessoriesMeasuring cup, Steaming basket Rice scoop
COOKWARM
Rice Cooking
Keep WarmSR-928
SR-GA421/SR-GA281SR-GA721 
						

							
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SR-GA421/SR-GA281/SR-GA721

WARNINGThis service information is designed for experienced repair technicians only and is not designed for use by the general public.It does not contain warnings or cautions to advise non-technical individuals of potential dangers in attempting to service a product.
Products powered by electricity should be serviced or repaired only by experienced professional technicians. Any attempt to service or 
repair the product or products dealt with in this service information by anyone else could result in serious injury or death.
There are special components used in this equipment which are important for safety . These parts are marked by 
 in the Schematic
Diagrams, Circuit Board Diagrams, Exploded Views and Replacement Parts List. It is essential that these critical parts should 
be replaced with manufacturer’s specified parts to prevent shock, fire or other hazards. Do not modify the original design without 
permission of manufacturer.
IMPORTANT SAFETY NOTICE
CONTENTS
1.SCHEMATIC DIAGRAM & WIRING DIAGRAM .....................................................................3-4
2.FUNCTION OF CENTER THERMOSTAT AND THERMAL FUSE .........................................
5-6
3.TROUBLE SHOOTING GUIDE  ...............................................................................................7-8
4.TESTING PROCEDURE .........................................................................................................9-10
5.EXPLODED VIEW & PACKING VIEW (SR-GA421/SR-GA281)  ............................................11-12
6.REPLACEMENT OF PARTS LIST & PACKING LIST
 (SR-GA421/SR-GA281)  ....................13-14
7.EXPLODED VIEW & PACKING VIEW (SR-GA721) ..............................................................15-16
8.REPLACEMENT OF PARTS LIST & PACKING LIST
 (SR-GA721) .......................................17-18
Page 
						

							
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SR-GA421/SR-GA281/SR-GA721

L
N
MICA HEATER ASS’YCAST HEATER
LAMP RESIST
.
T.F.
INPUT SWITC
H
LAMP RESIST.
KEEP W ARM NEON LAMP 
(BIG)
(SMALL
)
E
Green
RICE COOKING NEON LAMP 
Lamp Lead Wire A (Orange) Lead Wire (Orange)
Lamp Lead Wire C (Brown) 
Twist one time
Lamp Lead Wire B (Gray) 
Lever Earth Lead Wire (Green)
Silicone Tube (Blue)
N
T
wist two time
Thermal Fuse Wire (Gray)Switch Lead Wire (Blue)
Cord Wire Earth (Green)Silicone Tube (Green)
Silicone Tube (Brown)
Cord Bush10˚±5˚
Thermal Fuse Wire (Brown)
N
Cord Bush
Silicone Tube (Blue)Silicone Tube (Brown)
After ass’ y, Mica Heater Ass’ y must not overlie
the Outer Case of Center Thermostat.
Water guard
Cord Wire Earth (Green)Silicone Tube (Green)
Thermal Fuse Wire (Blue) Lever Earth Lead Wire (Spiral Green)
Wiring Lead Wire (Brown
) Lamp Lead Wire A (Red)Lamp Lead Wire C (Brown
)
Twist one time Thermal Fuse Wire (Gray)Lamp Lead Wire B (Gray)After assembly Mica Heater case
 
Must no touch the terminal of cast heat.
Glass tape 20 x 20 mm
.
After ass’y, gap between terminal and mica heater case must be more than 4 mm.
10˚±5˚
Cast Heater
Lamp Resistor
Lamp Resistor
SwitchKeep W arm Neon Lamp
Rice Cooking Neon Lam
p
Gra
y
Input Blue
Brown
N
L
E
Gree
n
Mica Heater Ass’y
T.F.
T.F.

1. SCHEMATIC DIAGRAM & WIRING DIAGRAM
SCHEMATIC DIAGRAM (SR-GA421)WIRING DIAGRAM (SR-GA421)
SCHEMATIC DIAGRAM 
(SR-GA281)WIRING DIAGRAM (SR-GA281) 
						

							
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SR-GA421/SR-GA281/SR-GA721

Cord Wire Earth (Green)
Cord Wire Blue (N) Cord Wire Brown (L)Heater lead wire B (grey)
Thermal fuse lead wire (Blue) Thermal fuse lead wire (Grey
)
User position Heater lead wire C (Brown)
Heater lead wire A (Red) Grey
Brown
Red
Cathode lead wire (Brown
)
Keep warm lamp lead (Red
)
10˚±5˚
MICA HEATER ASS’Y
CAST HEATER
LAMP RESIST.
SWITCH
LAMP RESIST.
KEEP WARM NEON LAMP 
RICE COOKING NEON LAMP 
(SMALL)
(MIDDLE)
(BIG)
E
GreenINPUT
L
N
Brown
Blu
e
1.F.T2.F.T

1. SCHEMATIC DIAGRAM & WIRING DIAGRAM
SCHEMATIC DIAGRAM (SR-GA721)
WIRING DIAGRAM (SR-GA721) 
						

							
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SR-GA421/SR-GA281/SR-GA721

2. FUNCTION OF CENTER THERMOSTAT AND THERMALFUSE
A. Center Thermostat
The center thermostat senses when the bottom of the rice cooker pan reach 134°C ± 6°C. 
And it’s action turns off the cooking cycle, and starts the warming cycle.
Refer to these figures showing the center thermostat construction and cooking position.  As 
the metal is heated, its ability to be attracted by the magnet decreases.
Finally, the inner spring pressure becomes stronger than the magnetic pull and the metal 
and magnet will pop apart. The rod activates the switch lever which causes the auxiliary lever to 
press the micro-switch button into the warming cycle.
B. Switch-On Preventive System
This is design to prevent the rice cooker from being turned on without the pan placed into 
position.
1) Normally when the pan is inserted properly into the rice cooker , the pan will depress the 
center thermostat. The center thermostat outer spring will be compressed. In this case when 
the switch button is depressed, the following will happen:
a. The auxiliary lever will release the micro-switch button. This puts the micro-switch in the 
cook position.
b. The switch lever will push the rod which will allow the magnet to meet with the metal.
c. When the rice is cooked and the proper temperature has been reached 134°C ± 6°C, the 
metal and magnet will pop apart as described in the center thermostat operation above.
d. The rod will push the switch lever and cause the auxiliary lever to depress the micro-
switch button. Th
is puts the micro-switch in the warming position.
2) When the pan is not in place w ithin the rice cooker, the center thermostat is not depressed.
a. In this condition, the outer spring is not compressed within the center thermostat 
preventing the metal from reaching its normal operating position.
b. When the switch button is depressed, the switch lever and auxiliary lever work as above 
but the magnet cannot come in contact with the metal to hold the switch lever in the cook 
position. This happens because the switch lever hits the t
hermostat case and cannot push 
the rod, with the magnet attached, all they way up to meet with the metal.
c. When the pressure is taken off the switch butto
n, the switch lever releases immediately to 
the open or warm positions.
Metal 
Magnet
  Inner spring 
Cooking heater
 
Rod 
10mm  Outer spring 
Switch lever  Cook switch button 
Micro switch 
Thermostat case
 
Thermostat surface 
Auxiliary lever 
Metal 
Magnet
  Inner spring 
Cooking heater
 
Rod  Inner spring  Outer  
spring  Switch lever
 Cook switch button 
Micro switch
 
NC 
C 
Center thermostat construction
(Cooking Position) (Warming or Off Position)Figure 1 
						

							
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SR-GA421/SR-GA281/SR-GA721

C. Thermal Fuse
The thermal fuse is used to open the circuit to the cooking heater when the temperature has 
gone unusually high. This happens in case
s such as incomplete contact between the heater 
and pan or if the switch buttons is forced to stay on keeping the heater energized abnormally .
This fuse is not a resetting device and must be replaced after openning.
Whenever replacing the fuse make sure the protective cover is placed over all exposed wiring.
Cause of Fusion
[A] Improper contract between heater and pan
2. FUNCTION OF CENTER THERMOSTAT AND THERMALFUSE
[B] Forced application of current
Cause
Pan collar or deformed
Foreign matter adheringBody dented or deformedPan bottom dented or 
deformed
Heater surface deformed 
or corroded
Remedy
Remove foreign matter 
by of (-) screw-driver, 
etc., and then polish with 
= 320 water paper while 
wetting it with water.Repair or replace body.
Replace pan.
Replace cooking heater.
Cause
Chopstick,  wooden 
piece, etc. inserted onto 
cooking button. (continu-
ous application of current)
Switch lever deformed 
or maladjusted, causing 
continuous application of 
current.
Remedy
Inserted to prevent ear-
lier turning off? Refer to 
cause in (a) above.
Repair or replace parts.
When fusion takes place, check the cause, set right the faulty section, and be sure to use 
replacement parts.  
						

							
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SR-GA421/SR-GA281/SR-GA721

3. TROUBLESHOOTING GUIDE
SymptomDiagnosisRemedy
Cooking function
● Cooking fails (Cooking 
lamp is not shown)
No continuity of cord?Yes ● Replace AC cord. 
No continuity of thermal fuse? Yes
 
● Locate cause for fusing and 
replace fuse. 
No continuity of micro switch?
Yes
 
● Replace 
Frame ass’y. 
Center thermostat is broken?
(Checked evaporation test) Yes
 
● Replace center thermostat. 
Switch lever properly adjust?
No 
● 
Adjust Switch lever. 
● Cooking fails (Cooking 
lamp is not shown)No continuity of sheathed heater? Yes
 
● Replace sheathed heater. 
● Thermal fuse blown
Forced application of current?
Yes
 
● Explain correct usage. 
●  Rice burns (Brown color)
Center thermostat defective?
(Check with evaporation test) Yes
 
● Replace center thermostat. 
 Switch lever has been properly adjusted?
No 
● Adjust Lever. 
Usage correct?
● Rice is not rinced well enough?
● Using with low rated voltage?
● 
Too much water input for cooking? Yes
 
● Explain correct usage. 
When receiving the cooker to be repaired, be sure to always take charge of not only the 
cooker body but also the pan and the lid, and ask for details as to the symptom of the trouble.
Furthermore, when making troubleshooting of each part, be sure to remove the power plug from 
the socket.
No 
No 
No 
No 
No 
Yes  
						

							
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SR-GA421/SR-GA281/SR-GA721

3. TROUBLESHOOTING GUIDE
SymptomDiagnosisRemedy
● Earlier Switching-off
● Poor cooking finish
Too hard
Too soft
Half-boiled
Poor contact between pan and sheathed 
heater? (Check with bubbling test)Yes 
● Replace pan or sheathed 
heater.
 
Center thermostat defective?
(Check with evaporation test) Yes
 
● Replace Center thermostat. 
Switch lever has been properly adjusted?
No 
● Adjust switch lever. 
Usage correct?
● Too small or large in rice quantit
y.
● Too small or large in water quantity.
● Switched off once by hand in cooking 
process.
● Switched off by shocks given in cooking 
process.
● Rice not untied.
 
● Explain correct usage. 
Keep warm function
● Warming fails (Warm lamp 
not shown)Micro switch change contact to NO (Warm 
mode) after cooking is done?
No 
● Adjust switch lever. 
● Warming fails (Warm lamp 
shown)
No continuity of warming heater? Yes
 
● Replace warming heater. 
No 
No 
Yes  
						

							
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SR-GA421/SR-GA281/SR-GA721

4. TESTING PROCEDURE
1. Bubbling testInput the pan in the main body, and lightly rotate the pan clockwise and counter clockwise 
to set the pan on the heating plate properly.
1.  Fill water until the center area of the pan bottom is dipped, and close the lid.  Then turn 
on the boiling switch.
2. When it beings boiling to produce steam, remove the lid and immediately check the 
bubbling condition on the pan bottom.
3. Bubbling condition is shown in figure 3.
A. Bubbles generate through out the circumference of the pan bottom ............... Proper
B. Bubbles does not generate on more than one quater part of the pan bottom 
circuference .................................................................................................. Improper
If it is improper, it may result from the insfficient contact between the pan bottom and 
the sheathed heater.
 Check the pan bottom and the sheathed heater for foreign material 
remained. Clean up the foreign materials or replace the parts.
2. Evaporation test
1. After satisfactory bubbling i s confirmed, remove the lid and put a weight on the cooker.
2. Cover the entire pan bottom with 2 or 3 pieces of tissue paper (or gauze), and turn on 
the switch subsequently.
3. Th
e cooker is considered acceptable if the timing when steam generation comes to 
a stop after water of the pan bottom has evaporated, is within 1 minute before and 
after the cooking switch is turned off. If these requirements are not satisfied, check the 
center  thermostat as well as the contacted condition between the pan bottom and the 
cooking heater, and then repair or replace the parts.
COOK
WARM
5 cm.
.mc 04
Pan (viewed from above)  Pan flange 
section 
Holes of 
tissue paper 
Tissue paper
 
Water Level
Sheathed heaterCenter thermostat
Figure 2Figure 3
Water Level
AB 
						

							
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SR-GA421/SR-GA281/SR-GA721

4. TESTING PROCEDURE
3. Boiling control lever adjustment
Such a mechanical operation as center thermostat goes up and down is used to turn on 
and off the micro
-switch. Check and adjust this relationship  as shown below.
 When the boiling switch is turned on. When the boiling switch is turned off.
 
CheckingThe auxiliary lever presses the push-
button (The “WARM” lamp comes on.)The auxiliary lever does not press 
the push-button (The “COOK” lamp 
comes on.)
AdjustingTo gain the above relationship, adjust the auxiliary lever by bending it with 
long nose pliers.