The Advanced
®
3D3/4D3 Service Manual
27
The 3D3/4D3 is comprised of the following
functional blocks:
Power Supply
The power entry assembly interfaces the AC
voltage presented to the instrument with the
transformer. The transformer provides 120
VAC to the power supply board and the head
motor. The power supply provides the power
to run the main printed circuit board (±12
VDC, ±5 VDC), the thermoelectrics (5 VDC),
the fan (12 VDC), the stir/freeze coil
(12 VDC), and the optional external printer
(12 VDC).
Front End
Although the 3D3 and 4D3 have physically
different front ends, the following description
applies to both.
The sample thermistor measures the tempera-
ture of the sample. The thermoelectrics
(whose duty cycle is controlled through the
block probe/thermistor) supercool the sample.
The stir/freeze wire constantly stirs the sam-
ple to guarantee uniform cooling. When the
supercooled sample reaches a set temperature
(3000 mOsm for the 3D3 in the low range
and 5400 mOsm for the 3D3 in the high
range; 3000 m°C for the 4D3), the stir/freeze
wire "buzzes" causing the sample to freeze.
During a test, the fan is on while the thermo-
electrics duty cycle is greater than 50%; oth-
erwise the fan is off. In between tests, the fan
runs on slow speed to provide cooling for the
electronics.
3D3600/4D3600 Main Control Board
Description
The 3D3 and 4D3 use the same main board
except for the EPROM (which contains the
software).
3D3/4D3 Circuit Description
(Hitachi Processor)
Power Supply
Head Motor
Controls
Serial Port
Electronics
Package
Cooling
System
Printer
Port
KeypadDisplay
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