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§520, 5525, & 5530 WARMING
CABINETS
4. Adjustments & Calibrations
After making the power supply voltage adjust-
ments, check for proper adjustments as follows:
'a.
Depress the temperature set point control
on the front control panel and the display
should read from 36° to 71°C.
18 VAC Voltage Check
a.
Connect DVM probes between J7 - Pin 1 and
Pin 2.
b.
DVM
reading should be 18.00 +3 -0 VAC.
24 VAC Voltage Check
a.
Connect DVM probes between J7 - Pin 9 and
Pin 10.
b.
DVM reading should be 24.00 +6 -0 VAC.
TEMPERATURE CONTROL CALIBRATION
U
HO ro
R26
R28
Calibrate the power supply voitage as outlined
under Power Supply Voltage Calibration before
making the Temperature Control Calibration.
Adjust 2.5 Vdc on the PCB display.
a.
Connect a DVM (digital voltmeter) negative
probe to J1 - Pin 6 and the positive probe to
J1 - Pin 2.
b.
Adjust
R28
if required
to provide
a DVM
reading of 2.500 +0.005 Vdc.
R23
J1
J2
I
CUT-OUT
|
3.
Adjust 2.0 Vdc on the PCB display.
Connect a temporary jumper from J1 - Pin 3 to
J1 - Pin 12 to turn on third digit in temperature
control display.
Connect a jumper from top of R29 to J1 - Pin 6.
Adjust
R23
so
that
the
display
reads
000.
Remove jumper between R29 and J1 - Pin 6.
One of two calibration procedures may be
used to calibrate the temperature sensor
which is a continuation of the Tempera-
ture Control Calibration Instructions.
NOTE]
Procedure |
Procedure | requires an ice/water bath to pro-
vide 0°C and a boiling water bath to provide 100°C
temperature for immersing the temperature sensor.
o
Remove the temperature sensor from the con-
trol box
assembly.
Remove
plug J6 from
the
PCB and jumper the red wire of TS (tempera-
ture sensor) to J6 - Pin 9 and the white wire of
TS to J6 -Pin 10.
Immerse tip of TS in the ice/water bath. Adjust
R41 so that the display reading is the same as
the
bath
temperature.
For
example,
if bath
temperature is 0.5°C, adjust display to read 005.
Immerse
tip of TS
in the boiling water
bath.
Adjust R40 so that the display
reading
is the
same as the bath temperature. For example,
if
the bath temperature is 100.0°C, adjust display
to read 1000.
i
Repeat
Steps
2 and
3 three
times
to assure
accurate adjustment.
Reassemble the temperature sensor to the con-
trol box assembly.
Reconnect
J6 to the PCB
and
remove
the
jumper from J1 - Pin 3 to J1 - Pin 12.
30926
19
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