Control Board Check - Hoshizaki KM-350MWJ Service Manual

C. Control Board Check
Before replacing CB that does not show a visible defect and that you suspect is bad,
always conduct the following check procedure. This procedure will help you verify your
diagnosis.
Alarm Reset: If CB is in alarm (beeping), press the "ALARM RESET" button on CB
while CB is beeping. WARNING! Risk of electric shock. Care should be
taken not to touch live terminals. Once reset, the icemaker starts at the
1-minute fill cycle. For audible alarm information, see "III.B. LED Lights and
Audible Alarm Safeties."
1) Check the dip switch settings to assure that S4 dip switch 3, 4, 7, 8, 9, 10 and S5 dip
switch 1 through 5 are in the factory default position. S4 dip switch 1, 2, 5, and 6 are
cleaning adjustments and the settings are flexible. For factory default settings, see
"III.C.1. Default Dip Switch Settings."
2) Move the control switch to the "ON" position and the mode switch to the "ICE" position.
If the red CB "POWER OK" LED is on, control voltage is good, continue to step 3. If CB
"POWER OK" LED is off, check CT secondary circuit. CT output is 10.5VAC at 115VAC
primary input. If the secondary circuit has proper voltage and the red LED is off, replace
CB.
If the secondary circuit does not have proper voltage, check CT primary circuit. Check
for 115VAC at CB K1 connector pin #10 (BK) to neutral (W) for 115VAC. Always choose
a white (W) neutral wire to establish a good neutral connection when checking voltages.
For additional checks, see "II.I.1. No Ice Production."
3) The "OUTPUT TEST" button provides a relay sequence test. Make sure the control
switch is in the "ON" position and the mode switch is in the "ICE" position, then press
the "OUTPUT TEST" button. For the correct lighting sequence, see the table below.
Note that the order of the LEDs from the outer edge of the control board is 1, 4, 5, 3, 2.
Components (e.g., compressor) cycle during the test.
Following the test, the icemaker begins operation at the 1-minute fill cycle. If the LEDs
do not light as described above, replace CB.
4) To verify voltage output from CB to the components, slide the CB K1 connector out far
enough to allow multimeter lead contact. With the icemaker in the cycle to be tested,
check output voltage from the corresponding pin on CB K1 connector to a neutral
(W wire). If output voltage is not found and the appropriate LED is on, replace CB.
5) Check CB control connectors K3, K4, and K5 for correct VDC per table below.
Legend: CB–control board; CT–control transformer
K3 Thermistor
Pin # VDC
#1 to #2 5VDC
#1 to #3 5VDC
#2 to #3 0VDC
K4 Bin Control
Bin Empty (closed)
Pin # VDC
#1 to #2 1VDC
#1 to #3 5VDC
#2 to #3 5VDC
21
ALARM RESET
K5 Float Switch
Pin # VDC
#1 to #2 1.2VDC
#1 to #3 2VDC
#2 to #3 1.2VDC
OUTPUT TEST
CB
Thermistor
Bin
Control
ON
Float Switch
1 2 3 4 5