CONTROL MODES and CONDITIONS
(Cont’d)
Automatic Mode: This is the operating mode of the 6750 Freezer/Mill. When the mill is
programmed, the tub is filled with liquid nitrogen, and a chilled grinding vial is in place, press
the RUN key. In Automatic Mode the mill will perform the following sequence: pre-cooling,
grinding period 1, cooling, grinding period 2, etc., until the programmed number of
grinding/cooling cycles is completed. The LED display will then blink “END” for about five
seconds, and revert to Program Mode.
Stop Mode: Pressing the STP key while the Freezer/Mill is running in Automatic Mode will stop
the run and return the mill to its current programmed settings. The LED display will blink
“END” for about five seconds, and then the display will return to Program Mode.
Manual Mode: This is a test mode which allows the mill to operate for about 3 seconds, without
beginning a programmed run, whether the mill is filled with liquid nitrogen or not. With the mill
in Program Mode, press the MAN key; the mill will run for several seconds and stop. The chief
use of Manual Mode is to verify by ear that the coil is functioning properly. To do this, place an
empty 6751 vial with its impactor in the coil; when the mill runs, the rattle of the impactor will
be clearly audible. See Pause Condition (below) for an alternate use of the MAN key.
Pause Condition: If you press the MAN key while the mill is running in Automatic Mode, the
mill will stop and the LED display will read “PAUSE.” To resume the grinding program where
it was interrupted, press the RUN key. To end the grinding program and return to the initial
program settings, press the STP key. (See Manual Control, above, for the other use of the MAN
key.)
Lid Fault Condition: When the lid is lifted, or if it is down but the safety interlock is not
engaged, the LED display will read “LID” and the mill cannot be run. This is to prevent the mill
from being accidentally run with the coil above the liquid nitrogen, or with a vial not held in
place by the coil gate. To return the Freezer/Mill to Program Mode, ready for running, close and
latch the lid. If the mill remains in Lid Fault Condition with the lid latched, the lid interlock
switch may be out of adjustment. If the lid opens unexpectedly during a run, the mill will stop.
To resume the run where it was interrupted, close and latch the lid; “RUN” will appear in the
display. Press the RUN key to resume grinding.
Liquid Nitrogen Fault Condition: If there is no liquid nitrogen in the Freezer/Mill, or the level of
liquid nitrogen in the tub is too low to cool the coil and vial properly, the display will blink “LN”
when the RUN key is pressed. To resume operation, fill the tub to the mark with liquid nitrogen,
close and lock the lid, and press the ENT key.
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