W
William J. Beaty
- Jan 1, 1970
- 0
Just in case others will be searching for this info: the 28VDC switching
power supplies in Bruker BLAX-300 RF amplifiers in Nuclear Magnetic
Resonance instruments tend to fail mysteriously right after power-cycling
(for example, after a building power outage.) We've had many of these do
this. Other NMR departments have reported it also.
In fact, the usual cause is dried-out filter capacitors in the tiny
"bootstrap" power supply which normally would give the switcher chip
it's 12VDC Vcc, in the brief time just before the main section wakes up.
(The switcher chip in the high-volt section powers itself! But before it
wakes up, it needs at least 9.0VDC for a fraction of a second.) If a
dried-out 100uF capacitor in the voltage-doubler bootstrap supply should
lower the output to 9VDC, then the main supply wakes up sometimes, but
not always. (So go and cycle power a few times, you might get lucky.)
If it drops below 9VDC, it won't wake up at all.
More info is at:
University of Washington CES
Archive of tricks, info, etc.
http://staff.washington.edu/wbeaty/chemtrik.html
((((((((((((((((((((((( ( ( (o) ) ) )))))))))))))))))))))))
William J. Beaty Research Engineer
[email protected] UW Chem Dept, Bagley Hall RM74
[email protected] Box 351700, Seattle, WA 98195-1700
ph206-543-6195 http//staff.washington.edu/wbeaty/
power supplies in Bruker BLAX-300 RF amplifiers in Nuclear Magnetic
Resonance instruments tend to fail mysteriously right after power-cycling
(for example, after a building power outage.) We've had many of these do
this. Other NMR departments have reported it also.
In fact, the usual cause is dried-out filter capacitors in the tiny
"bootstrap" power supply which normally would give the switcher chip
it's 12VDC Vcc, in the brief time just before the main section wakes up.
(The switcher chip in the high-volt section powers itself! But before it
wakes up, it needs at least 9.0VDC for a fraction of a second.) If a
dried-out 100uF capacitor in the voltage-doubler bootstrap supply should
lower the output to 9VDC, then the main supply wakes up sometimes, but
not always. (So go and cycle power a few times, you might get lucky.)
If it drops below 9VDC, it won't wake up at all.
More info is at:
University of Washington CES
Archive of tricks, info, etc.
http://staff.washington.edu/wbeaty/chemtrik.html
((((((((((((((((((((((( ( ( (o) ) ) )))))))))))))))))))))))
William J. Beaty Research Engineer
[email protected] UW Chem Dept, Bagley Hall RM74
[email protected] Box 351700, Seattle, WA 98195-1700
ph206-543-6195 http//staff.washington.edu/wbeaty/
