M-Audio Hammer 88 Pro, Service Manual, Page: 34 / 44

3) Check if A1 chip is working properly:
a) Check whether A1 (U4) chip circuit and SPI FLASH (U11) welding is normal.
b) Test whether there is 12MHz waveform on crystal oscillator resistor R1/R3 to determine whether
the crystal oscillator circuit is normal.
c) Check whether the PIN1 of reset chip U6 rises to 3.3V and appears about 40ms later than the
power supply when it is powered on. If abnormal, check the relevant circuit.
d) Test whether the associated signal to SPI FLASH is normal. If all the above are normal, A1 and SPI
FLASH chips need to be replaced.
2. No response from function buttons
1) Check the cable connection between the keyboard circuit, the function board and the mainboard.
2) Check whether each key button is installed correctly.
3) No response when pressing the keyboard:
a) Check the ribbon cable on the keyboard circuit, the ribbon cable/socket between the keyboard
circuit and the mainboard are properly soldered or if it’s damaged.
b) Check the mainboard’s 88 ‐ key socket to A1 keyboard PIN, check if it’s properly soldered or if
there’s short ‐ circuit.
4) No response when pressing the control buttons:
a) Check if the buttons and LED circuit are properly soldered.
b) Check if the key circuit welding is normal, whether there is virtual welding, leakage welding.
c) Make sure that the wiring and sockets connected from the key board to the main board are welded,
connected or damaged.
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