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Head Up/Down Test Advanced

™

Osmometer 3250/Cryoscope 4250 Service Manual

Note Your instrument is equipped with a series of diagnostic LEDs on the main application

board PCB605 to allow visual identification of drive signals and sensor activation.

• The yellow LEDs marked Drive Up and Drive Dn indicate that the control

electronics have issued a command to the head motor relays.

• The red LEDs marked Head Up and Head Dn indicate that the corresponding

optical sensor has been tripped.

Head Up/Down Test

1. Turn on the instrument. If there is a Supervisor/Operator keyswitch, turn it to the

Supervisor position (if required).

2. Place an empty sample tube in the sample well.

3. Press TEST.

4. Press < or > to select Head Up/ Down Test, and then press START.

5. Place an empty sample tube into the freezing chamber.

6. At [START] Test [STOP], press START.

The head should move continually up and down.

7. Use this test to ensure the following components are working properly:

– The motor [A] is running.

– The gears [B] are turning properly.

– The sensors [C] are detecting the head-up and head-down conditions.

– The sample well fluid passage [D] is not obstructed by debris, and the pump is

moving the heat transfer fluid into the freezing chamber.

Note If the sample well fluid passage is obstructed, disassemble and clean the sample well

following the instructions found earlier in this section. Also, examine the one-way

check valve [E] to make sure it is not stuck open or closed.