R-86STMA (serv.man9). Touch Control Panel Assembly — Sharp Home Appliance Service Manual (repair manual)

Model
R-86STMA (serv.man9)
Pages
2 Few pages! See other manuals at the bottom of the first or last page.
Size
91.66 KB
Type
PDF
Document
Service Manual
Brand
Device
Home Appliance / Microwave Oven / Touch Control Panel Assembly
File
r-86stma-sm9.pdf
Date

View Sharp R-86STMA (serv.man9) Service Manual online

R86STMA
9 – 1
R86STMA
Service Manual
 
CHAPTER 9. 
TOUCH CONTROL PANEL ASSEMBLY
[1] 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 signals communicated
among them are explained below.
1. Key Unit (Graphic sheet + Membrane switch)
The key unit is composed of a matrix, signals generated in the LSI are
sent to the key unit from P40 - P47.
When a key pad is touched, a signal is completed through the key unit
and passed back to the LSI through P20, P21, P22 and P00 to perform
the function that was requested.
2. Control Unit
Control unit consists of LSI, power source circuit, synchronizing signal
circuit, reset circuit, buzzer circuit, relay circuit, temperature measure-
ment circuit, indicator circuit and back light circuit.
1) LSI
This LSI controls the temperature measurement signal, key strobe
signal, relay driving signal for oven function and indicator signal.
2) Power Source Circuit
This circuit generates voltage necessary in the control unit.
3) Synchronizing Signal Circuit
The power source synchronizing signal is available in order to com-
pose a basic standard time in the clock circuit. It accompanies a
very small error because it works on commercial frequency.
4) Reset Circuit
A circuit to generate a signals 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 completion sound).
6) Stop Switch
A switch to “tell” the LSI if the door is open or closed.
7) Relay Circuit
To drive the magnetron, grill heating element, bottom heating ele-
ment, convection motor, fan motor, turntable motor, touch control
transformer and light the oven lamp.
8) Back Light Circuit
A circuit to drive the back light (Light emitting diodes LD1 - LD10).
9) Indicator Circuit
This circuit consists 7-digits, 26-segments and 4-common elec-
trodes using a Liquid Crystal Display.
10)Temperature Measurement Circuit: (OVEN THERMISTOR)
The temperature in the oven cavity is sensed by the thermistor. The
variation of resistance according to sensed temperature is detected
by the temperature measurement circuit and the result applied to
LSI. The LSI uses this information to control the relay and display
units.
Symbol
Voltage
Application
VC
-5.2V
LSI(IC1)
R86STMA
9 – 2
[2] SERVICING FOR TOUCH CONTROL PANEL
1. Precautions for Handling Electronic Components
This unit uses CMOS LSI in the integral part of the circuits. When han-
dling these parts, the following precautions should be strictly followed.
CMOS LSI have extremely high impedance at its input and output ter-
minals. For this reason, it is easily influenced by the surrounding high
voltage power source, static electricity charge in clothes, etc., and
sometimes it is not fully protected by the built-in protection circuit.
In order to protect CMOS LSI.
1) When storing and transporting, thoroughly wrap them in aluminium
foil. Also wrap PW boards containing them in aluminium foil.
2) When soldering, ground the technician as shown in the figure and
use grounded soldering iron and work table.
2. Servicing of Touch Control Panel
We describe the procedures to permit servicing of the touch control
panel of the microwave oven and the precautions you must take when
doing so. To perform the servicing, power to the touch control panel is
available either from the power line of the oven or from an external
power source.
1. Servicing the touch control panel with power supply of the
oven:
CAUTION: THE HIGH VOLTAGE TRANSFORMER OF THE MICRO-
WAVE OVEN IS STILL LIVE DURING SERVICING AND
PRESENTS A HAZARD.
Therefore, before checking the performance of the touch control
panel,
1) Disconnect the power supply cord, and then remove outer case.
2) Open the door and block it open.
3) Discharge high voltage capacitor.
4) Disconnect the leads to the primary of the power transformer.
5) Ensure that these leads remain isolated from other components
and oven chassis by using insulation tape.
6) After that procedure, re-connect the power supply cord.
After checking the performance of the touch control panel,
1) Disconnect the power supply cord.
2) Open the door and block it open.
3) Reconnect the leads to the primary of the power transformer.
4) Reinstall the outer case (cabinet).
5) Reconnect the power supply cord after the outer case is installed.
6) Run the oven and check all functions.
a) On some models, the power supply cord between the touch
control panel and the oven is so short that the two can't be sep-
arated.
For those models, check and repair all the controls (sensor-
related ones included) of the touch control panel while keeping it
connected to the oven.
b) On some models, the power supply cord between the touch
control panel and the oven is long enough that they may be sep-
arated from each other. For those models, therefore, it is possi-
ble to check and repair the controls of the touch control panel
while keeping it apart from the oven; in this case you must short
both ends of the door sensing switch (on PWB) of the touch
control panel with a jumper, which brings about an operational
state that is equivalent to the oven door being closed. As for the
sensor related controls of the touch control panel, checking
them is possible if the dummy resistor(s) with resistance equal
to that of the controls are used.
2. Servicing the touch control panel with power supply from an
external power source:
Disconnect the touch control panel completely from the oven, and
short both ends of the door sensing switch (on PWB) of the touch
control panel, which brings about an operational state that is equiv-
alent to the oven door being closed. Connect an external power
source to the power input terminal of the touch control panel, then it
is possible to check and repair the controls of the touch control
panel; it is also possible to check the sensor-related controls of the
touch control panel by using the dummy resistor(s).
3. Servicing Tools
Tools required to service the touch control panel assembly.
1) Soldering iron: 60W
(It is recommended to use a soldering iron with a grounding termi-
nal.)
2) Oscilloscope: Single beam, frequency range: DC - 10MHz type or
more advanced model.
3) Others: Hand tools
4. Other Precautions
1) Before turning on the power source of the control unit, remove the
aluminium foil applied for preventing static electricity.
2) Connect the connector of the key unit to the control unit being sure
that the lead wires are not twisted.
3) After aluminium foil is removed, be careful that abnormal voltage
due to static electricity etc. is not applied to the input or output ter-
minals.
4) Attach connectors, electrolytic capacitors, etc. to PWB, making
sure that all connections are tight.
5) Be sure to use specified components where high precision is
required.
approx. 1M ohm
Page of 2
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Here you can view online or download Sharp R-86STMA (serv.man9) Service Manual in pdf. This Service Manual can help you recover, restore, fix, disassemble and repair Sharp R-86STMA (serv.man9) Microwave Oven. Information contained in Sharp R-86STMA (serv.man9) service manual (repair manual) typically includes:

  • Disassembly, troubleshooting, programming, maintenance, remote, adjustment, installation and setup instructions.
  • Schematics, wiring and block diagrams.
  • Printed wiring boards (PWB) and printed circuit boards (PCB).
  • Parts list (bill of materials).