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Technical Service Manual
MPA160 and MPA161
DigiMelt
Student Melting Point
System
Stanford Research Systems
Revision 0.7 (February 2010)
DigiMelt Technical Service Manual
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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
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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