Veichi AC310 Service Manual page 50

Digital tube repair in accordance with the above digital tube connection diagram
and diode repair can be judged good or bad.
The U2 in this circuit is an 8-bit 3-state shift register/output latch chip, check whether the
⚫
voltage on the left and right side of the chip is abnormal, and whether pin 16 is supplied
with 5V; the pull-up resistor of the chip is 10K on pins 1 to 7 and pin 15, corresponding
to the voltage of 5V; the pull-up resistor of pins 10, 11, 12 and 14 is 4.7K, and the level
of the pull-up is 5V; the voltage of pin 13 is 3.3V. (Note: damage to the pull-up resistor
will cause the chip to work abnormally, so it is necessary to measure the pull-up resistor);
an abnormality of this chip will lead to the cathode of the segment selection LED or a
digital light of the chip selection. 3.3V, (Note: damage to the pull-up resistor will cause
the chip to work abnormally, so it is very necessary to measure the pull-up resistor);
abnormalities in the chip will lead to problems with the cathode of the segment-selected
LEDs or with the chip-selected digital light, which will lead to no display or fewer strokes;
in the keypad circuit, the most important is the keypad CUP U13, which requires 5V for
the chip to operate (pin 6),damage to this chip leads to abnormalities in the keypad and display
circuits, so this chip is the core of the keyboard circuit.
4. Device bit number and specification
Name/Bit
number
Programmable
IC
Logic chip
Digital tube
When the key is
pressed
U13=XMC1100-T016F0032
Resistors and capacitors connected to the chip
Pin 16: Resistor R144=10K/0402, connect to 5V voltage
Resistors on pins 13 and 14 are R262 and R268 in that order,
both 10Ω/0402.
Pin 6, connected to 5V, also connected to GNG Capacitance:
C18/C80 = 2.2UF
U2=74HC595D
Resistor and capacitor connected to the chip
Resistor: R59=R85=R90=R56=R276=10K/0402
R234=R203=R283=R284=R285=R286=R287=R288=R2
89=0402 Capacitor:C20=C23=2.2UF/0402
JH-3505ASR1AK（common anode）
Pushbutton S1 circuit:
AC310 Universal AC Drive Service Manual
Model Quantity
1
1
1
49