Intrlogic Test Points And Jumpers; Common Diagnostics - Thermo Scientific 3403 Manual

Section 8
Appendices

Common Diagnostics

IntrLogic Test Points
and Jumpers
8-2 Midi 40 CO2 Incubator
• If all displayed values show "Err" on the display in the main loop,
ensure there are no out-of-range voltages at the ADC input (see Test
Points on the CPU board). Specifically, if the unit utilizes TC CO2
control, ensure the sensor harness to the sensor is connected properly.
If this sensor becomes disconnected the TC input on ADC channels 0
and 1 are ~5.4 to 5.5 VDC and will cause all ADC channels to fail.
Technically, this violates an absolute maximum rating for the LTC2408
ADC of Vcc +0.3 VDC (5.3 VDC). To date, no permanent ADC
failure due to this problem has been identified; however, this situation
should be avoided.
• If the CO2 display is not stable and for example displaying 4.0%,
5.2%, and then 6.0% and it cycles through this display cycle (or
similar) every display update (16 seconds), ensure the fan is rotating. If
not, check the door switch, AC fan signal, and any obstruction that
may prevent the fan from rotating.
• If the water RTD display is showing an extremely high value and the
cabinet probe RTD is displaying a normal value, ensure that the water
RTD and the cabinet RTD are not switched.
Table 7-2. Test Points
Test Point Description
CPU TP1 ADC Ch 0: CO2 (+) Sensor 2.3-2.4VDC Typical
CPU TP7 ADC Ch 1: CO2 (-) Sensor TC only; IR=N/C
CPU TP9 ADC Ch 2: Rh Sensor 3.677VDC Typical
CPU TP10 ADC Ch 3: Water Temperature Sensor 105mVDC Typical
CPU TP11 ADC Ch 4: Ambient Temperature Sensor 105mVDC Typical
CPU TP12 ADC Ch 5: Chamber Temperature Sensor 105mVDC Typical
CPU TP13 ADC Ch 6: Tank Switcher
CPU TP14 ADC Ch 7: nc / line voltage / O2 Sensor 8mv Typical
CPU TP2 5 VDC (regulated from line or battery)
CPU TP6 4.5 VDC Reference
CPU TP15 -1.6 VDC Offset (H05 version only)
CPU TP4 Battery Voltage 15.3VDC typical
CPU TP5 -5 VDC (H05 version only)
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