Human Humalyzer 2000 - Page 9

Rev. B ' 7
brackets provide adjustments in both horizontal and vertical dimensions, so that the filament can
be centered on the light path. The lamp must be replaced if output becomes low or the lamp fails
completely. To check for low lamp output, run test #186. Press MENU, then type 186 and press
ENTER. The instrument prints the detected voltage for each filter. The printout shows the
wavelength, position, and the voltage for each filter. The voltages should be between 2 and 10
volts. If all or most of the voltages are low, the lamp is the likely suspect. As a final check,
measure the voltage at the lamp terminals. If the lamp voltage is much lower than 4.5 VDC, the
regulator circuitry on the main PCB (Q6 and VR1) may be the problem. Otherwise, replace the
lamp. Refer to the section “Lamp Replacement”.
The photometer PCB contains a photodiode, a very sensitive op amp circuit and phototransistors.
Because the photodetector and related circuitry is solid-state, it should require no service. Do not
attempt to modify the photometer PCB.
The filter wheel turns on a shoulder screw shaft and is driven by the filter wheel motor via a
neoprene belt. The filter wheel itself requires no adjustments. The optical interference filters
contained in the wheel are of metal deposition type construction and are intended to be
maintenance free for the life of the instrument. However, in a non-ideal environment where
extreme humidity or temperature are encountered, optical characteristics on one or more filters
may be compromised. Run test # 186 as described above. If only one or two filter voltages are
low, the filter(s) may be suspect. Refer to the service procedure “Filter Replacement”.
Flowcell
If proper care is taken to clean the flowcell between uses, especially after highly proteinaceous
liquids have been sampled, the flowcell itself should require little or no maintenance.
The flowcell should be cleaned regularly as described in "Cleaning the Flowcell". If the
flowcell tubing has become damaged or the flowcell is clogged, the flowcell can be disassembled
for cleaning and parts replacement. Refer to the service procedures “Flowcell Tubing
Replacement" and “Flowcell Disassembly”.
Erratic readings (excessive dither) may be a result of trapped air in the flowcell. This can be
caused by improper installation of, or failure of the flowcell tubing or coupling tubes. See the
section "Flowcell Tubing Replacement’. Check the insertion depth of the flowcell tubes into the
coupling tubes. Ensure that a leak-free seal is made and that no tubes are kinked or pinched off.
Valve |
The valve uses a short length of silicone tubing. If the valve operates but no sample is drawn up,
the pinch valve tubing may be blocked. To check for clogged valve tubing, unscrew the flowcell
vacuum line from the Luer fitting. Press PURGE and listen for aspiration. If you hear aspiration,
the valve is operating, but the flowcell is clogged. If you do not hear aspiration, the valve tubing
is clogged. See the section “Valve Tubing Replacement”.
Humalyzer 2000 Service Manual