Human Humalyzer 2000 - Troubleshooting; Power Supply; Photometer

6 Rev. B
Troubleshooting
The instrument incorporates solid-state electronics in a-very reliable field-proven design. In this
section, each subassembly or component group is discussed, possible problems and solutions are
outlined.
Power Supply
The power supply consists of a transformer, two diode bridges, and three regulators. Line
voltage supplied to the transformer is converted to 36 VAC, center tapped, which feeds diode
bridge BR2. The center tap is used as a reference for regulators VR4 and VRS, which provide
+15 VDC and -15 VDC for analog circuitry. Another transformer output supplies 11 VAC to
diode bridge BR1, which provides +12VDC (raw, 11-13 VDC nominal) to the system, and VR3
regulates this down to +5 VDC for the logic and other low voltage control circuits.
A "dead" instrument may be just a blown fuse. However, a blown fuse may indicate a problem
on the main PCB or transformer. Also, the voltage select switch setting must match the line
voltage. If there is no voltage present at J6, check the fuse. To replace the fuse, disconnect the
power cable and open the instrument. Remove the two #4 screws holding the AC cover to the
rear panel and lift the AC cover off towards the front of the instrument. Locate the double clip
fuse holder mounted on the inside of the rear panel. Locate the blown fuse and remove it with a
fuse puller, or carefully pry it out with a small screwdriver. Install a 0.6A 3AG slow blow fuse.
Use only the recommended fuse. Do not substitute other rating! Replace the AC cover.
If voltage is present at J6, check for input voltage on VR3, VR4, and VRS. If no voltage is
present, the diode bridge BR1 or BR2 may have failed.
Photometer
The photometer assembly can be examined as several component systems:
. Read well assembly and cell heat PCB
. Lamp and brackets
. Photometer PCB
* Filter wheel and motor.
The read well assembly serves to hold the tube or flowcell centered on the cell block, between a
fixed plate and a spring loaded plate. Mechanical adjustments are not required. The presence of a
tube or flowcell is detected by an opto pair (phototransistor and IR LED) mounted at the ends of
the cell heat PCB. A stainless steel plunger in the bottom center of the cell block forces a small
spring plate into the light path between the opto pair.
The lamp is tungsten-halogen, rated at 6V, 10W, and is intended to be maintenance free for the
life of the instrument, since the lamp is turned off automatically after 30 minutes of instrument
inactivity. However, under heavy usage the lamp remains on for longer periods and may require
replacement as the output becomes low near the end of its service life. In addition, a physical
shock to the instrument may necessitate lamp replacement due to filament breakage. The lamp
and lens brackets simply hold the lamp and lens in alignment with the rest of the assembly. The
Humalyzer 2000 Service Manual