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5. Maintenance
5.9
6.
Use an Allen key (2.5 mm) to unscrew the upper of the two
screws securing the lamp holder and the lamp. Note carefully the
positions of the insulation sleeve and washer.
7. Disconnect the lamp from the PC-board.
8. Bend the upper part of the lamp holder slightly (2-3 mm)
upwards and withdraw the mercury lamp from it by gently
pulling the metal socket.
9. Insert the new mercury lamp and connect it to the PC-board.
10. Remount the upper lamp holder screw, ensuring that the
insulations are correctly mounted, reinstall the cell holder and
perform the maximum light adjustment described in Section 5.8.
Mercury lamp
- maximum
light
adjustment
Warning:
During this adjustment stray light may escape from the
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
UV source and protective glasses must be worn.
Connect the optical unit to the control unit and plug into the
mains supply.
Switch on the instrument and allow to warm up for about
10 minutes.
Insert a filter and the corresponding converter or aperture.
Connect the control unit to a recorder with a full scale response
of 50 mV.
Set the range selector to SHORT and zero the recorder.
Set AU/ %T to % T and turn the baseline adjust fully clockwise.
Select a range giving a pen deflection of approx. 50 % and then
rotate the lamp around its longitudinal axis until maximum pen
deflection occurs.
Set the range selector to SHORT and adjust the recorder zero to
bring the pen to the centre of the chart. Mark this pen position.
Set the range selector to 2 and set AU/ % T to AU.
Adjust the baseline control to its mid-position, five full turns
from either end of its range, by means of a tool, ie. an adjustable
spanner.
If necessary, adjust the lamp by turning it slightly to bring the
pen back to the position marked in step 8.
Reassemble the optical unit.
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