Control Board Check - Hoshizaki DCM-271BAH-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.
• 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 connector pin closest to CB black
K3 connector 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, power
supply cord, and power switch). Next, check for proper 24VAC output from CT. Next,
check that 1A fuse is good. Check for 24VAC from CB K8 connector pin #1 (W/R) to
CB K8 connector pin #2 (LBU). If 24VAC is not present, check control switch continuity.
If open while in the "ICE" position, replace control switch. 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, 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).
(1) 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 connector
pin #1 and pin #2 are open. 5VDC is present between CB K9 connector
pin #1 (W/BK) and pin #2 (W/BK). If not, check control switch position and
continuity (open). Replace as needed. Next, confirm 5VDC between pin
#1 (W/BK) and CB red K4 connector, pin closest to CB black K3 connector. If 5VDC
is not present, replace CB.
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