Vulcan-Hart 126172, Service Manual

Page: 35 / 68

ELECTRIC COMBI OVENS - SERVICE PROCEDURES AND ADJUSTMENTS
Page 35 of 68
BATTERY BACKUP -
PROGRAMABLE CONTROL
The battery backup module allows the SRAM (static
ram) to retain the configuration and program
information in memory if there is a power loss. The
battery backup may come in a two piece
configuration of an SRAM chip mounted onto a
battery module or a one piece SRAM and battery
module combination. The 28 pin non-volatile
SRAM/Battery module is located on the CPU board.
Unless power to the oven is interrupted and then
restored, a low voltage battery condition would
otherwise not be detected.
Battery Test
1. Disconnect power from the oven, then turn the
power back on.
2. The control board will perform a power up
diagnostic test, sound the buzzer and turn the
displays and lights on then off.
A. If the displays go blank and lights turn off
on the control, then the battery backup is
functioning properly.
B. If oven or control will not power up, see
“TROUBLESHOOTING” section for a list
of possible causes.
C. If code numbers appear in the time and
temperature display or the control
operation is erratic, the battery backup
may be malfunctioning.
1) Press the keypad ON button. If
dashes “- - -“ are displayed in the
time display and 888c is displayed in
the temperature display, then battery
module voltage may be low.
WARNING: DISCONNECT THE ELECTRICAL
POWER TO THE MACHINE AT THE MAIN
CIRCUIT BOX. PLACE A TAG ON THE CIRCUIT
BOX INDICATING THE CIRCUIT IS BEING
SERVICED.
2) Remove the right side panel as
outlined under “COVERS AND
PANELS”
3) With the power disconnected from
the oven, check the battery module
voltage while mounted on the CPU
board. Measure the voltage between
pins 14 and 28 on the SRAM chip. If
voltage is less than 3VDC, then
replace the SRAM/Battery module
combination (one or two piece) as
outlined below in “BATTERY
REPLACEMENT” and repeat battery
test.
NOTE: SRAM/Battery backup module
voltage can not be measured without first
being mounted on the CPU board and
powered at least once.
NOTE: Do not use a battery backup
labeled ISSI on the top. This type of
battery backup quickly drains the SRAM
resulting in an 888c display error.
3. The oven should now operate properly.