17 cannot use remote communications commands, Service – American Magnetics 05200PS-430-601 Integrated Power Supply System User Manual

Page 163

Rev. 5

145

Service

Troubleshooting Hints

proper current for the installed switch. Excessive currents cause

excessive boiloffs. The typical switch requires approximately 45 mA

to function correctly. Refer to the documentation provided with the

magnet for proper operating current. See Figure 3-13 on page 75.

2. Verify that the protective diodes on the magnet are not turning on.

Damaged diodes may short causing current to flow through them

whenever magnet current flows and cause excessive heating. This

can be identified by observing a change in the apparent field-to-

current ratio since some of the current is bypassing the coil. If the

boil off rate returns to normal with the magnet de-energized, this

may indicate a defective diode.

3. Ensure that there are no inadvertent thermal paths between the

cryogenic environment and the 300K environment. Ensure all

transfer lines are removed from the cryostat; check the position of

break-away vapor-cooled current leads.

4. Ensure the LHe level sensor is not continuously energized if

continuous level indication is not necessary.

5. Ensure the vacuum in vacuum-jacketed dewars is of sufficiently

low pressure.

5.2.16 Cannot display the magnetic field strength, only current

Note

Setup menu limits are always required in terms of current.

5.2.17 Cannot use remote communications commands.

1. Verify your communications cable integrity and wiring. Refer to

remote communications connectors.

2. Check to make sure you are sending the correct termination to the

Model 430 Programmer. If you are using RS-232, make sure the

baud rate, number of stop bits, and data bits/parity settings of the

host device are matched to those of the Model 430 Programmer (see

section 4.3). If you are using Ethernet communications, check all

Model 430 Programmer network settings (see sections 3.10.4 and