Jeff de Ropp
UCD NMR Facility
jsderopp@ucdavis.edu
Phone: 916-752-7677
FAX: 916-752-3516
NMR Facility URL http://www.nmr.ucdavis.edu
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>From charlie@telemann.pse.umass.eduWed Nov 15 08:16:55 1995
Date: Wed, 15 Nov 1995 05:21:51 -0500
From: leonard charles dickinson <charlie@telemann.pse.umass.edu>
To: jsderopp@ucdavis.edu
We had an ecoupler on the AMX500 we bought 2.5 years ago and Bruker replaced
it 8(eight!) times before it was replaced by a BLTH100 proton amplifier. We
have had not trouble since then. Our trouble was across-the-board reduced
power or no output. We found particularly that doing composite pulse
decoupling which is perhaps similar to your rapid rep time on the 10mm probe
usually took the ecoupler out.
My advice is damn the ecoupler and get a BLTH100 otherwise this sort
of problem will go on and on. It interfaced easily with our AMX though it
did require converting all hl? power statements to tl? and dl? which is
a bit of a pain but worth it if you can rely on you proton amp.
Best of luck...
Charlie Dickinson
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|Dr. L.Charles Dickinson voice mail and office (413)5771428 |
|Director of NMR Instrumentation lab telephone (413)545-0630, -5413 |
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Have you checked for problems in the preamp housing? Relay
contacts can become lossy. I have had two problems in this area and
in both cases the BB/Matching drawer was defective (problem was in
the X-nucleus path). A progressive mismatch over time might produce
your symptoms. When you experience your power loss does retuning
correct it?
(No it doesn't. J de Ropp)
Sincerely,
Andy.
----------------------------------------------------------------------
Andy Soper.
School of Pharmaceutical Sciences. Electronics Section.
Rhodes University. P. O. Box 94, 6140 Grahamstown,
South Africa (The 'Rainbow People' Country).
Voice: +27 (0)461 318412 FAX: +27 (0)461 311205
Internet: paas@giraffe.ru.ac.za
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>From gmb@research.bfg.comWed Nov 15 10:52:00 1995
Date: Wed, 15 Nov 1995 11:54:16 -0500
From: "George M. Benedikt - x5448" <gmb@research.bfg.com>
To: Jeffrey Deropp <jsderopp@ucdavis.edu>
Subject: Re: Ecoupler problems
I noticed your posting on e-coupler problems. How do you measure the 15% drop
in output?
(Pulsing through attenuator into calibrated scope. J. de Ropp)
I experience problems with my similar e-coupler when doing homo
decoupling in liquids using the hi2 mode of the e-coupler. I measured on a
breakout box voltages of a few millivolts as oposed to about 1 volt.
Looking forward to the responses you received.
George M. Benedikt
BFGoodrich
Brecksville, Ohio
-- George M. Benedikt - x5448 ********************************************** >From greg@gossinst.demon.co.ukThu Nov 16 15:19:41 1995 Date: Thu, 16 Nov 1995 22:30:16 +0000 From: Greg Coumbarides <greg@gossinst.demon.co.uk> To: jsderopp@ucdavis.edu Subject: ecouplerYour problems with the ecoupler seem similar to some we had recently. As part of the NMR services we offer, we repair NMR RF power amplifiers.
The answer may be to look at the power supply for the amplifier. Most pulse power amplifiers work on a maximum of 10% duty cycle, and use a bank of big electrolytic capacitors to supply the large pulses of energy required. When the pulse occurs, the capacitors discharge energy and then recharge relatively slowly from the power supply. If you pulse again too quickly the capacitors do not have enough time to recharge, resulting in a lower energy for the next pulse. Most manufacturers use a power supply which is small in comparision with the output power of the amplifier. One exception to this is AMT as anyone who has tried to lift an AMT amplifier will tell you.
Hope this helps.
Greg Coumbarides Goss Scientific Instruments Ltd 100 Vicarage Lane, Great Baddow, Essex, CM2 8JB, England Phone +44 1245 478441, Fax +44 1245 473272
**************************************************** >From 102363.2156@compuserve.comFri Nov 17 09:14:12 1995 Date: 15 Nov 95 14:05:10 EST From: peter <102363.2156@compuserve.com> To: Jeffrey Deropp <jsderopp@ucdavis.edu> Subject: Ecoupler problems
Jeff,
The first thought coming to my mind reading your e-mail is that the decoupler power value on 0dB is not controled i.e. there is no feed back control for this value. All other power values (i.e. HL = 1...120dB) are controlled. So the question is: What power level are you using for your experiment? (Various power levels hl1 = 0 to 3 have shown problem. J. de Ropp) If you experience the problem only for shorter times and you are using your ecpoupler in the range from 1..120dB it could be that the control time constant is to high. Maybe there is a inofficial fix to make that constant a little smaller to serve your purpose.
Regards
Peter Sprenger ******************************************************* >From lintner@chem.psu.eduFri Nov 17 09:14:19 1995 Date: Wed, 15 Nov 1995 13:40:54 -0500 From: John Lintner <lintner@chem.psu.edu> To: jsderopp@ucdavis.edu Subject: ecoupler
Jeff, Your message regarding your ecoupler problem was relayed to me here at Penn State through Juliette Lecomte. WE experienced a similar problem with our H/F 500 ecoupler. I am working on the assumption that your ecoupler has the same mechanical configuration as ours - I've never seen an H only model. In any case, what I did to ours was to mount the amplifier block, on what I will call, its back, to expose the heatsink. To expand on this, take a large sheet of aluminum and mount the amp. block outside of the original chassis, but directly alongside, this will allow you to use the existing wiring harness. You will have to use some 'L' angle for brackets. With the heatsink now exposed upward you can build a simple assembly and mount 2 or 3 fans directly above the heatsink. I positioned our fans so they would blow down onto the heatsink. I used an aluminum sheet that allowed me to reinstall this configuration in the area within the power bay where the ecoupler had come from. Pay attention to securely mounted assemblies and grounding to avoid any loops. Good luck. John Lintner 814-863-1182