American Magnetics 420 Power Supply Programmer - Manual (Page 118)

100 Rev. 7
Service
Troubleshooting Hints
either by a voltmeter on the front of the supply or by a DVM
measurement. If the supply output voltage is approximately zero,
the resistance of the power leads (not the Model 420) is dictating
the maximum ramp down rate. An energy absorber is necessary to
increase the rampdown rate.
5.2.7 The Model 420 will not charge the magnet to desired field.
1. If the power supply ramps to full output current after the supply
output voltage exceeds approximately 0.7 V, verify the polarity of
the power supply protective diode. Ensure the protective diode
remains installed across the output terminals of the power
supply with the anode at the
1(* ative terminal and the cathode at
the 326 itive terminal.
2. Ensure the voltage and current adjust controls on the front of the
power supplies are in their fully clockwise position. Refer to the
operations manual for the specific power supply for more
information regarding the adjustment of the manual voltage and
current controls when the supply is remotely programmed.
3. Ensure that the Model 420 supply setup submenu is configured to
match the connected power supply, e.g. check that the Model 420 is
configured for the proper voltage-to-voltage programming range
according to paragraph 3.2.1.6 on page 43.
5.2.8 The four quadrant power supply will only supply current in
one direction
1. Ensure the Model 420 is configured to allow negative power supply
voltages according to paragraph 3.2.1.2 on page 42 and negative
power supply currents according to paragraph 3.2.1.4 on page 42.
2. Verify that the Model 420 is configured for the proper voltage-to-
voltage programming range according to paragraph 3.2.1.6 on
page 43.
5.2.9 The Model 420 will not place the magnet in persistent
mode.
1. Ensure there is adequate LHe level in the cryostat to allow the
persistent switch to cool to the superconducting state.
5.2.10 The Model 420 will not bring the magnet out of persistent
mode.
1. With the persistent switch heater on, press the 1 key in the default
display to show the switch heater voltage. A value of 0 V indicates a
shorted switch heater connection. A value exceeding 17 V indicates