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1 Technical Service Manual MPA160 and MPA161 DigiMelt Student Melting Point System Stanford Research Systems Revision 0.7 (February 2010) DigiMelt Technical Service Manual 2 Precautions THIS TECHNICAL SERVICE MANUAL IS INTENDED SOLELY FOR USE BY QUALIFIED REPAIR TECHNICIANS. DANGEROUS POWER LINE VOLTAGES ARE PRESENT IN THIS PRODUCT. ONLY PERSONNEL FAMILIAR WITH POWER LINE VOLTAGE SAFETY PROCEDURES SHOULD ATTEMPT TO REPAIR DIGIMELT Power-on error messages DigiMelt normally displays the firmware version number for 2 seconds at power-on. The following error messages indicate failed self-checks in the power-on sequence: Err 7 The User Offset Calibration has been cleared. Re-enter your desired User Offset Calibration. See "User Temperature Calibration" (Page 5) for details. Err 8 Burn-in mode is enabled. DigiMelt will cycle between room temperature and 250 C every 30 minutes. Remove Test Jumper JP1 before returning the unit to service. Never allow the user to operate DigiMelt in this condition! Err 9 The Factory installed calibration data is corrupted so the unit is no longer calibrated. Return the unit to SRS for recalibration. Major Error Indications The following error displays indicate a broken unit. If either display appears, disconnect the unit from the power line and remove it from service: 799.0 A temperature reading of 799 C is used to indicate that the RTD is either open or shorted. The actual oven temperature is unknown, but the CPU will not apply power to the oven in this condition. Repair the RTD wiring, if possible. Otherwise, the unit must be returned to SRS for a new sample oven and calibration. Flashing display and alarm sound Unplug the line cord immediately! The sample oven temperature is above 280 C. This can only be caused by a short in the heater control circuit. See "Runaway Heat" in the troubleshooting section. DigiMelt Technical Service Manual 3 Circuit Description Please see "SRS MPA160 7-01780-701E Schematic" for the Printed Circuit Board. Please see "SRS Assembly 316 Schematic" for the all electrical components that are not on the PCB. Line Voltage DigiMelt uses a standard power entry module with both line and neutral legs switched and fused at 1 Amp (115 VAC units) or