Slot machine failure repair 1

     1 only when the lower right-two light zero:
    First, adjust the IC board main power supply voltage is +5 V, and then check the 8015 (CPU) ninth pin reset terminal from high to low, if not, check the boot RESET circuit U4 (555) third pin output and the second pin Input is normal, and then check the C4 capacitor is normal.
    2. Boot all of the seven-segment display (8 words) show random number display:
    This failure for many reasons, some of the main parts of the problem may cause this situation, usually first check the CPU (8051); then check the RAM, ROM and 8910,8279; and then check the address line, data lines are wrong; See U7 18,19 feet CLOCK whether the signal is normal (see the quartz crystal oscillator is normal action).
    3. When the boot appears below 01:
    Most of this situation is the need to use the boot program, the implementation of boot action, there may be RAM (6116) failure.
    4. Boot appears below 02:
    There is 02 code table for the general problem, first check the code table, and then check the code table drive circuit U6 (75452), U6 input signal U7 (8051) provided, and then check the code table checksum circuit U12 , U13 (PC817) is normal.
    5. There is no normal music sound, but there is noise:
    First check +12 V is not supplied to the IC board, and then check the U20 (LM380) and U14, U16 (8910), but the noise sometimes from the power circuit malfunction, pay special attention.

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