American Magnetics 420 Power Supply Programmer - Manual (Page 115)

Rev. 7 97
Service
Troubleshooting Hints
d. Replace the fuse and securely fasten the instrument top cover.
Reconnect the power-cord.
3. Verify the input voltage selector switch on the instrument’s printed
circuit board is in the proper position for the available input power.
Checking the input voltage selector requires removal of the top
cover of the instrument. Observe the same safety procedures as
presented in step 2, above.
5.2.2 The Model 420 does not remember the operating setpoints
after power is removed.
Warning
This procedure is to be performed only when the instrument is
completely de-energized by removing the power-cord from the power
receptacle. Failure to do so could result in personnel coming in
contact with high voltages capable of producing life-threatening
electrical shock.
1. Ensure the instrument is de-energized by disconnecting the power
cord from the power source. Disconnect the power cord from the
connector located on the rear panel of the instrument.
2. Remove the instrument top cover and replace the computer
memory backup battery, BT1.
Note
When replacing the battery, replace with a 3.6 volt AA-size lithium
cell (International size reference: ER14505). Comply with the
polarity markings adjacent to the battery holder on the printed
wiring board.
Warning
Do not attempt to recharge the Lithium cell. Attempts at recharging
may cause the cell to vent or explode.
5.2.3 The power supply is unstable, causing the magnet current
to oscillate.
1. Verify the power supply is configured for remote programming,
voltage-to-voltage mode. Consult the manufacturer’s operations
manual for the necessary power supply configuration.
2. Verify that the persistent switch heater is operating. Also, verify
that the actual persistent switch in the magnet is correctly
installed and connected.