Bunn JDF Silver Series, Technical Training Manual

JDF Silver Series Training Manual

14

Both transformers are 120VAC on the primary side and step the voltage down to 24VAC on 

the secondary side of the transformer. Each transformer is protected on the “load” side with 

a resettable PTC fuse. The Poly Switch Polymeric Positive Temperature Coefficient (PPTC) 

device used on the load side of the transformers will help protect against harmful over/cur-

rent surges, voltage and over/temperature faults. The PPTC device will reset after the fault 

is cleared and power to the circuit is removed.

Dispense Lockout Switch (C)

The dispense lockout switch is located on the bottom front behind the drip tray. The switch is used to 

lockout the dispense functions of the dispenser to prevent unauthorized use of the dispenser, while 

keeping the refrigeration system running. Early juice machines before the release of the program 

switch also used the dispense lockout switch to enter the water bath fill mode, semi-automatic sani

-

tizing mode and brixing test modes.

A field retrofit kit is available to convert old style JDF-S machines to the new style should a customer request it. The 

PN for the retrofit kit is 44140.0000 and applies only to mechanical switch dispensers. At this time a kit is not offered 

for membrane switch models. Installation of the retrofit kit is considered elective and is not covered by warranty. Re

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fer to service bulletin 189 for details regarding the change.

Compressor Relay K1 (D)

The compressor relay is the component that will pass 120VAC power to the 

compressor. By switching the refrigeration to the on position, 120VAC will be 

present on one contact terminal waiting to pass on. The relay coil (K1) will 

receive 120VAC from the main control board after a 6 minute delay from initial 

plug-in and energize, closing the relay contacts. With the contacts closed 

120VAC will pass across the contact and onto the compressor limit thermostat 

and energize the compressor start and run winding.

Control Board Assembly (CBA) (E)

The CBA is powered by receiving 24VAC from one of the step down 

transformers. The CBA microprocessor will receive input signals and in 

return will control a sequence event or an output of power to the other 

components used throughout the machine. The CBA is responsible of 

converting 24VAC to D/C voltage to support the voltage adjustment 

dials located at the bottom of the CBA for the pump motor rpm ,cabinet 

fan and dispense valve. The pump speed adjustment dials range 9 to 

24VDC. 

Other power distributed is 120VAC to inlet valve, compressor run relay, 

transformer and condenser fan motor. The CBA will further step down 

the voltage to 5VDC for door switches, dispense lockout switch and 

water and bath thermistor.

CBA Connector Identification (BUNN P/N: 40177.1000)

J-1: 120VAC supply to the CB for inlet water valve, 120VAC output to 

water valve

J-2: Pump motor 1 and 2 and water valves 1 and 2

J-3: Cabinet fan

J-5: Dispense lockout switch

J-6: Power/Lower transformer (Transformer B)

J-7: Cabinet thermistor

J-8: Not used

J-9: Water bath thermistor

J-11: Door auxiliary board

J-12: Right power for stations 3 and 4 (Transformer A)

J-13: Pump motor 3 and 4 and water valves 3 and 4

J-15: Not used

PPTC

1

J1

J2

J3

J5

J6

J7

J9

J8

J13

J11

J15

J12

2

1
2
3

4
5

1
2
3

4
5
6

1

2

3

6
5
4

1 2

1 2

2 1

1
2

3

4

1

2

3

4

5

3 2 1

3
2

1

1 3

2 4

Left

Station

Middle Left 

Station

Middle Right 

Station

Right

Station

Relay Coil - Labeled K1

On Wiring Schematic

Relay Contact