American Magnetics 430, Installation, Operation And Maintenance Instructions

Page: 206 / 254

190 R
EV
9
A
MERICAN
M
AGNETICS
, I
NC
. S
ERVICE
: T
ROUBLESHOOTING
H
INTS
ing 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 pres-
sure.
C
ANNOT
D
ISPLAY THE
M
AGNETIC
F
IELD
S
TRENGTH
, O
NLY
C
URRENT
Enter a coil constant in accordance with directions on page 81.
NOTE
Setup menu limits are always required in terms of current.
C
ANNOT
U
SE
R
EMOTE
C
OMMUNICATIONS
C
OMMANDS
1. Verify your communications cable integrity and wiring. Refer to page 203 and
page 204 for wiring of 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 page 143). If you are using Ether-
net communications, check all Model 430 Programmer network settings (see
page 104).
3. Check your host communications software and make sure it is recognizing
the return termination characters from the Model 430 Programmer. The
return termination characters are
<CR><LF>
.
4. If the Model 430 Programmer is responding repeatedly with errors, try a
device clear command (DCL) or powering the Model 430 Programmer off
and then back on. Be sure you are sending valid commands.
M
AGNET
C
URRENT
D
RIFTS
U
NACCEPTABLY
W
HILE
C
OOLING
P
SWITCH
1. Set the PSwitch Cooling Gain to 25% (see page 88) and cool the switch.
Observe the current on the front of the Model 430 Programmer while the per-
sistent switch is cooling
2. If the switch will not lock (cool to superconducting), resulting in a PSW lock
error, reduce the PSwitch Cooling Gain by several percent and attempt cool-
ing the switch again.
3. If the switch cools but the magnet current has excessive drift during cooling,
increase the PSWitch Cooling Gain value by several percent.