DOWNLOAD Sharp R-750AM (serv.man5) Service Manual ↓ Size: 33.42 KB | Pages: 7 in PDF or view online for FREE

Model
R-750AM (serv.man5)
Pages
7
Size
33.42 KB
Type
PDF
Document
Service Manual
Brand
Device
Home Appliance / Microwave Oven / Test procedure and touch control assembly
File
r-750am-sm5.pdf
Date

Sharp R-750AM (serv.man5) Service Manual ▷ View online

4
750A -
TEST PROCEDURES
A
TOUCH CONTROL PANEL ASSEMBLY TEST
The touch control panel consists of circuits including semiconductors such as LSI, ICs, etc. Therefore,
unlike conventional microwave ovens, proper maintenance cannot be performed with only a voltmeter
and ohmmeter.
In this service manual, the touch control panel assembly is divided into two units, Control Unit and Key
Unit, and troubleshooting by unit replacement is described according to the symptoms indicated.
1.  Key Unit
The following symptoms indicate a defective key unit. Replace the key unit.
a) When touching the pads, a certain pad produces no signal at all.
b) When touching a number pad, two figures or more are displayed.
c) When touching the pads, sometimes a pad produces no signal.
2.  Control Unit
The following symptoms indicate a defective control unit. Replacing the control unit.
2-1  In connection with pads.
a) When touching the pads, a certain group of pads do not produce a signal.
b) When touching the pads, no pads produce a signal.
2-2  In connection with indicators
a) At a certain digit, all or some segments do not light up.
b) At a certain digit, brightness is low.
c) Only one indicator does not light.
d) The corresponding segments of all digits do not light up; or they continue to light up.
e) Wrong figure appears.
f) A certain group of indicators do not light up.
g) The figure of all digits flicker.
2-3  Other possible problems caused by defective control unit.
a) Buzzer does not sound or continues to sound.
b) Clock does not operate properly.
c) Cooking is not possible.
d) Proper temperature measurement is not obtainned.
B
KEY UNIT TEST
PROCEDURE
COMPONENT TEST
If the display fails to clear when the STOP/CLEAR pad is depressed, first verify the flat ribbon cable is
making good contact, verify that the door sensing switch (stop switch) operates properly; that is the
contacts are closed when the door is closed and open when the door is open. If the door sensing switch
(stop switch) is good, disconnect the flat ribbon cable that connects the key unit to the control unit and
make sure the door sensing switch is closed (either close the door or short the door sensing switch
connecter). Use the Key unit matrix indicated on the STOP/CLEAR pad making momentary contact. If
the control unit responds by clearing with a beep the key unit is faulty and must be replaced. If the control
unit does not respond, it is a faulty and must be replaced. If a specific pad does not respond, the above
method may be used (after clearing the control unit) to determine if the control unit or key pad is at fault.
KEY UNIT
1 min.
AUTO
DEFROST
DUAL
GRILL
GRILL
LESS
g • oz
Kg • Lb
Kg / Lb
MORE
AUTO
COOK
TIMER
STOP/
CLEAR
10 sec.
10 min.
MICROWAVE
POWER
LEVEL
CONVENI
-ENCE
FOODS
START
CLOCK
AUTO
MINUTE
AUTO
START
G 1
G 2
G 3
G 4
G 5
G 6
G 7
G 8
G12
G11
G10
G 9
5
750A -
PROCEDURE
LETTER
COMPONENT TEST
C
RELAY TEST
1. CARRY OUT 3D CHECKS.
2. Disconnect the leads from the primary of the high voltage transformer. Make sure that the leads remain
isolated from other oven components and chassis. (Use insulation tape if necessary.)
3. Close the door.
4. Reconnect the supply.
5. Check the voltage between Pin Nos. 1 and 3 of the 3 pin connector (A) on the control unit with an A.C.
voltmeter. The meter should indicate 240 volts, if not check oven circuit.
6. RY1, RY2 and RY3 TEST
   These are operated by D.C. voltage. Check voltage at the relay coil with a D.C. voltmeter during the
microwave cooking operation.
DC. voltage indicated .............. Defective relay.
DC. voltage not indicated ........ Check diode which is connected to the relay coil. If diode is good,
control unit is defective.
RELAY SYMBOL
OPERATIONAL VOLTAGE
CONNECTED COMPONENTS
RY1
APPROX. 25.0V D.C.
Oven lamp / Turntable motor / Cooling fan motor
RY2
APPROX. 25.0V D.C.
Grill heater
RY3
APPROX. 25.0V D.C.
High voltage transformer
D
PROCEDURES TO BE TAKEN WHEN THE FOIL PATTERN ON THE PRINTED WIRING
BOARD(PWB) IS OPEN
NOTE: *At the time of these repairs, make a
visual inspection of the varistor for burn-
ing damage and examine the transformer
with tester for the presence of layer short-
circuit (check primary coil resistance). If
any abnormal condition is detected, re-
place the defective parts.
CARRY OUT 4R CHECKS.
To protect the electronic circuits, this model is provided with a fine foil pattern added to the primary on
the PWB, this foil pattern acts as a fuse. If the foil pattern is open, follow the troubleshooting guide
given below for repair.
Problem: POWER ON, indicator does not light up.
CARRY OUT 3D CHECKS.
STEPS
OCCURANCE
CAUSE OR CORRECTION
1
The rated AC voltage is not present at
Check supply voltage and oven power cord.
POWER terminal of CPU connector (CN-A).
2
The rated AC voltage is present at primary
Low voltage transformer or secondary circuit defective.
side of low voltage transformer.
Check and repair.
3
Only pattern at "a" is broken.
*Insert jumper wire J1 and solder.
(CARRY OUT 3D CHECKS BEFORE REPAIR)
4
Pattern at "a" and "b" are broken.
*Insert the coil RCILF2003YAZZ between "c" and "d".
(CARRY OUT 3D CHECKS BEFORE REPAIR)
RY2
OL / FM
/ TTM
AC
5
1
D20 
VRS1
a
b
d
c
CN - A
D21 
RY1
(J1)
T1
TEST PROCEDURES
6
750A -
TOUCH CONTROL PANEL ASSEMBLY
OUTLINE OF TOUCH CONTROL PANEL
The touch control section consists of the following units as
shown in the touch control panel circuit.
(1) Key Unit
(2) Control Unit
The principal functions of these units and the signals
communicated among them are explained below.
Key Unit
The key unit is composed of a matrix, signals R60, R61,
R62, R63, R72 and R73 generated in the LSI are sent to
the key unit.
When a key pad is touched, a signal is completed
through the key unit and passed back to the LSI through
R50, R51, R52 and R53 to perform the function that was
requested.
Control Unit
Control unit consists of LSI, power source circuit, syn-
chronizing signal circuit, ACL circuit, buzzer circuit and
indicator circuit.
1) LSI(IC1)
This LSI controls the key strobe signal, relay driving
signal for oven function and indicator signal.
2) Power Source Circuit
This circuit generates voltages necessary in the control
unit.
Symbol
Voltage
Application
VC
-5V
LSI(IC1)
3) Synchronizing Signal Circuit
The power source synchronizing signal is available in
order to compose a basic standard time in the clock
circuit. It accompanies a very small error because it
works on commercial frequency.
4) ACL Circuit
A circuit to generate a signal which resets the LSI to the
initial state when power is supplied.
5) Buzzer Circuit
The buzzer is responsive to signals from the LSI to
emit audible sounds (key touch sound and comple-
tion sound).
6)  Door Sensing Switch (Stop Switch)
A switch to “tell” the LSI if the door is open or closed.
7) Relay Circuit
To drive the magnetron, fan motor, turntable motor, grill
heater and light the oven lamp.
8) Indicator Circuit
This circuit consists of 4-digits, 12-segments and 3-
common electrodes using a Liquid Crystal Display.
9) Back Light Circuit
A circuit to drive the back light (Light emitting diodes
LED1-LED4).
7
750A -
LSI(IZA856DR)
The I/O signal of the LSI(IZA856DR) are detailed in the following table.
Pin No.
Signal
I/O
Description
20.0 msec
H : +5V
L : 0V
(Grill or dual)
ON
OFF
During
cooking
L
GND
H.
1-3
SEG21-
OUT
Terminal not used.
SEG23
4
COM1
OUT
Common data signal: COM1.
Connected to LCD (Pin No. 1)
5
COM2
OUT
Common data signal: COM2.
Connected to LCD (Pin No. 2)
6
COM3
OUT
Common data signal: COM1.
Connected to LCD (Pin No. 3)
7
COM4
OUT
Terminal not used.
8
VLC
IN
Signal synchronized with commercial power source frequency.
Signal similar to VSS.
9
VSS
IN
Power source voltage: 0V.
VSS voltage of power source circuit input.
10
XIN
IN
Internal clock oscillation frequency setting input.
The internal clock frequency is set by inserting the ceramic filter oscillation circuit
with respect to XOUT terminal.
11
XOUT
OUT
Internal clock oscillation frequency control output.
Output to control oscillation input of XIN.
12-15
K00-K03
IN
Terminal to change functions according to the Model.
DC voltage in accordance with the Model in operation is applied to set up its function.
16
TEST
OUT
Connected to VC.
17
RESET
IN
Auto clear terminal.
Signal is input to reset the LSI to the initial state when power is supplied. Temporarily
set  to "L" level the moment power is supplied, at this time the LSI is reset. Thereafter
set at "H" level.
18
HOLD
IN/OUT
Connected to VDD.
19
INT2
IN
Signal synchronized with commercial power source frequency.
This is the basic timing for time processing of LSI.
20
R81
IN
Terminal not used.
21
INT1
IN
Terminal not used.
22
R83
OUT
Terminal not used.
23
R90
IN
To input signal which communicates the door open/close information to LSI.
Door open "L" level signal (0V).  Door close "H" level (+5V)
24-25
R91-R92
OUT
Terminal not used.
26
VDD
IN
Connected to GND.
27
R40
OUT
Signal to sound buzzer (2.0 kHz).
A: key touch sound.
B: Completion sound.
28
R41
OUT
Grill heating element driving signsl.
To turn on and off the grill heating element
relay (RY2). "L" level during grill cooking
or dual cooking; "H" level otherwise.
A
B
0.1 sec.
2 sec.
H : +5V
L: 0V
H : +5V
L: 0V
TOUCH CONTROL ASSEMBLY/ DESCRIPTION OF LSI
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  • DOWNLOAD Sharp R-750AM (serv.man5) Service Manual ↓ Size: 33.42 KB | Pages: 7 in PDF or view online for FREE
  • Here you can View online or download the Service Manual for the Sharp R-750AM (serv.man5) in PDF for free, which will help you to disassemble, recover, fix and repair Sharp R-750AM (serv.man5) Microwave Oven. Information contained in Sharp R-750AM (serv.man5) Service Manual (repair manual) includes:
  • Disassembly, troubleshooting, maintenance, adjustment, installation and setup instructions.
  • Schematics, Circuit, Wiring and Block diagrams.
  • Printed wiring boards (PWB) and printed circuit boards (PCB).
  • Exploded View and Parts List.