Fisher Scientific 282A, Instructions Manual, Page: 22 / 25

21
SERVICE
CAUTION: Any service to be performed on the oven should be done by trained personnel.
Correcting a malfunction in the Model 282A primarily involves replacing the defective component.
Components
that can be replaced are listed under Table 11: Replacement Parts, page 18. Most components can be accessed
by removing the right side panel. There are six screws that hold the panel to the oven chassis.
Heater replacement is a much larger task, requiring near complete disassembly of the oven by two persons.
Therefore it is recommended that when required, heaters be replaced by returning the oven to a Fisher
service center. It should be noted that, because of the very low watt density of the heater elements, an
almost indefinite life is expected.
Because the Model 282A is equipped with self-diagnostic features, the service recommendations here are
limited to the Trouble Analysis Chart shown below which incorporates these features. To use this chart
effectively, select the Symptom category(s) that best describes the observable malfunction, in particular the
error codes. Proceed to inspect the
Probable Cause
description(s) and take the necessary
Corrective Action
.
Table 10: Trouble Analysis Chart
Symptom Probable Cause Corrective Action
Oven does not heat. CRC
error. Error found in
calibration data. Recalibrate unit.
Oven does not heat. OTC
error. Open Control
Thermocouple Check T.C. continuity; replace if open.
Oven does not heat. Open triac Check triac located on large heatsink.
Oven heaters Check resistance of each heating element.
Resistance should be between 14.00 and
17.12 Ohms. Replace if defective.
Heater power turned off
during program
execution. Enter Program Edit Mode. Check current
step for heater operation.
Oven does not heat. OVR
error. Open safety sentinel Push RESET button on sentinel. Replace
sentinel if unable to reset. Sentinel is
preset to trigger when heater temperature
exceeds approximately 300ºC.
Pressure readout indicates
wrong pressure. Calibration incorrect. Perform Calibration procedure in this
manual.
Offset value incorrect. Change offset so display value matches
actual chamber pressure.
Temperature readout
indicates wrong
temperature. Calibration incorrect. Perform Calibration procedure in this
manual.
Offset value incorrect. Change offset so display value matches
actual temperature.
Vacuum readout indicates
atmospheric pressure with
vacuum being drawn on the
oven. PURGE valve open.
VACUUM valve closed. Close PURGE valve.
Open VACUUM valve.
Faulty door seal. Regrease or replace seal.
Internal tygon tubing
between inlet port and Reconnect tubing.