Keypad Display Circuit - Veichi AC310 Service Manual

key identification function. Pressing different keys generates different voltages, so that the CPU
(the CPU (U13) is the keypad CPU, which is different from the CPU of the control board) can
read which key is working, and the corresponding digital tube can display the corresponding
value; there are 6 physical keys, corresponding to: RUN, UP (up key), PGR; DOWM (down
key), STOP/RESET, SET; the key circuitry of AC300CON1-V1.0 is the same as the keypad
circuitry of the control board. There are 6 physical keys, corresponding to: RUN, UP (up key),
PGR; DOWM (down key), STOP/RESET, SET; key circuitry:
2. Fault type
No display, no action or mis-action of keys
3. Inspection methods
Keyboard key failure, power on, check whether the 5V power supply is normal, and then
go to measure the corresponding resistances, capacitance is normal, the circuit, fewer devices,
easy to troubleshoot
4. Device bit number and specification
RUN, UP (Up key), PGR group circuit
devices:
Resistor: R269=7.5K/0402，
R163=20K/0402 R35=R151=100K/0402,
R158=10K/0402
Capacitor: C38=10NF/0402

3.7.2 Keypad Display Circuit

1. Circuit description: In the display circuit , using a common anode digital tube, common
anode digital tube characteristics of the positive pole of a uniform high level; in the display
circuit is the most important is the corresponding U13 keyboard CPU and U2 latch chip, to
make the common-anode digital tube digital tube is effective, according to the segment
selection of the cathode of the LED as well as the chip selection of the digital tube, the given
low level, you can display the corresponding data.
2. Type of fault: No display, display less strokes
3. Overhaul method
Digital tube overhaul
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AC310 Universal AC Drive Service Manual
DOWM, STOP/RESET, SET group
circuit devices:
Resistor: R161=7.5K/0402 ，
R270=10K/0402 R178=20K/0402,
R176=100K/0402
Capacitor: C38=10NF/0402
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