Control Board Check - Hoshizaki DCM-270BAH-OS Service Manual

C. Control Board Check
Before replacing a 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. Before proceeding, check for proper voltage per appliance nameplate. Check
that the 24VAC 1A fuse is good and 115VAC 3A GM external protector is closed.
NOTICE! Control Board Change:
• Control board 2A4296-01 and 2A8084-01 are no longer available.
• Control board 2A9093-01 replaces 2A4296-01 and 2A8084-01.
• Check the S1 dip switch settings to assure that they are in the factory default position.
For factory default settings, see "III.C.1. Default Dip Switch Settings." S1 dip switch
7 determines bin control application. WARNING! Do not adjust S1 dip switch 4, 7, 8,
or 9 dip switches out of their factory default positions. These dip switches must
be left in the factory default position or the appliance will not operate correctly.
• When checking for 115VAC high-voltage (primary), always choose a 115VAC
neutral (W) to establish a good neutral connection.
• When checking for 24VAC low-voltage (secondary), always choose a 24VAC
neutral (LBU) to establish a good neutral connection. If the appliance is in alarm, see
"III.B. LED Lights and Audible Alarm Safeties."
• When checking for 5VDC, use CB red K4 pin #1 (pin closest to CB black K3) to
complete DC circuit.
1) Startup-"POWER OK" LED on: Move control switch to "ICE" position, then move
power switch to "ON" position. "POWER OK" LED turns on. "POWER" LED remains on
unless power supply is interrupted. Diagnosis: Check that "POWER OK" LED is on.
If not, check for proper 115VAC supply voltage to CT (main breaker or fuse and power
switch). Next, check for proper 24VAC output from CT. Next, check that 1A fuse is good.
Check for 24VAC from CB K8 pin #1 (W/R) to CB K8 pin #2 (LBU). If 24VAC is present
and "POWER OK" LED is off, replace CB.
2) 5VDC Output Checks: There are seven 5VDC circuits on the appliance.
a) 3 circuits at CB K9 connector: Control switch "DRAIN" position, high-pressure switch
(HPS), and compressor control relay (CCR).
b) 2 circuits at CB K8 connector: Bin control (BC) and float switch (FS upper and
lower).
c) 2 circuits at CB K7 connector: Ice dispense (push button, and OS sensor), and water
dispense (push button and OS sensor).
2a) 5VDC CB K9 Connector: See Fig. 1.
a) Control Switch"DRAIN" Position
CB K9 connector pins #1 (W/BK) and #2 (W/BK):
• "ICE" Position: When the control switch is in the "ICE" position, CB K9 pin #1 and
pin #2 are open. 5VDC is present between CB K9 pin #1 (W/BK) and pin #2
(W/BK). If not, check control switch position and continuity. If open, replace control
switch. Next, confirm 5VDC between CB K9 #1 (W/BK) and CB red K4 pin #1 (pin
closest to CB black K3). If 5VDC is not present, replace CB.
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