Kipp&Zonen Brewer MkIII - Manual (Page 20)

MKIII SERVICE MANUAL 15
4.6 LIGHT DETECTION SYSTEM FAILURE
A Light Detection System failure may show up in any or all of the diagnostic or measurement tests
of the Brewer. In Lamp diagnostics it will usually be shown on the Computer Display as "Lamp Not
On .. test terminated” message. In a measurement (DS for example), the counts may simply go to
zero, or some other incorrect number, depending on the nature of the failure. Results of Lamp tests
are predictable so an HG and/or SL should be attempted if there is any suspicion of a Light
Detection problem.
The Light Detection System is comprised of the foreoptics, spectrometer, micrometers, slit mask,
and the PMT (including the high speed amplifier). Adjustments of any of these assemblies should
be done with extreme caution, unless they are specified in this manual, as Instrument calibration
may be affected.
4.7 TROUBLE-SHOOTING THE LIGHT DETECTION SYSTEM
1. Confirm Motor Positions are Correct
If Lamp tests fail and the message "Lamp not on test terminated" is displayed, the SL command
should be issued. With the lamp on, the correct positions of the zenith prism, filterwheels, and iris
should be confirmed. The correct positions are printed to the screen when the SL command is
issued. Light from the lamp should seen in both view tubes.
2. Test Photon Counting Circuit
If the SL test fails the photon counting circuitry should be tested.
Turn off the power, remove the ribbon cable from the PMT output, and plug it into J22 of the Main
Electronics Board. This connector is the output of a 1MHz Pulse Simulator (see picture).
Turn on the Brewer power and from the Main Menu enter the Teletype command, TT. At the
teletype prompt, enter the command R,0,7,20;O. The display should show 8 numbers, each being
approximately 2,280,140 counts. Exit TT by pressing the Home key, turn off Brewer power, replace
the PMT cable, and turn power back on.
If the test is normal, the Counting System is operating correctly.
Now check components in the Spectrometer.
3. Check Micrometer Position
In a low light level and dry room, remove the Brewer cover and the Spectrometer cover. Confirm
that the micrometers are in the correct positions as indicated on the ‘Micrometer Position’ log sheet
that is taped to the Spectrometer cover.
4. Check Mirror and Grating
Check that the spherical mirrors, the gratings, and the two flat mirrors appear to be in place, and
that their mounting assemblies appear normal. ** TAKE CARE NOT TO TOUCH THE SURFACES
OF EITHER THE MIRRORS OR THE GRATINGS AS PERMANENT DAMAGE MAY OCCUR **** .
4 OPERATING TEST FAILURES