I'm hoping one of the very helpful people on this list can give me some
advice on diagnosing a bad PTS.
Two days ago, our Inova 600 started dropping signals intermittently, and it
has gotten worse. The problem only occurs on channel 1 - thanks go to
Christine Hofstetter at Varian for reminding me that I can swap channels.
Everything behaves completely normally if I use channel 2 (rfchannel='2134')
which rules out any problems downstream starting from the AMT which was my
initial suspicion. This does however make it difficult to run triple res
experiments.
I've ruled out the xmtr and xmtr controller boards by swapping them
individually, as well as the wavegens and the attenuator board. That mostly
leaves the frequency synthesizer (PTS) or I suppose one of the little cards
that hang off the back. I suspect something is overheating since single
pulse experiments seem unaffected, and if the instrument sits idle for a
while I can collect a few traces normally before the signal drops out.
We have a spare PTS D620 from an old 500 console - one channel is dedicated
500 MHz, but the other is full band and I could swap the components for the
bad channel on the current unit. However, I'd like to be completely sure it
IS the PTS before trying that. If I just look at the frequency output on a
scope, it seems normal - 1H is aliased several times but is the same on ch.1
and ch. 2, low band nuclei come at the expected frequency +20 MHz I.F.
So, does anyone have any tips on how to diagnose PTS problems, or
alternately see anything else I'm missing?
Thanks, and for everyone in the U.S., have a good 4th of July weekend.
Andrew
--
Dr. Andrew Fowler | University of Iowa
Associate Director | B291 Carver Biomedical Research Building
Medical NMR Facility | Iowa City, IA 52242
319-384-2937 (office) | 319-335-7273 (fax)
andrew-fowler_at_uiowa.edu
Received on Fri Jul 02 2010 - 10:07:25 MST