AMMRL: Bruker AM Graphics Display Processor - Offset Adjust
Neil Jacobsen (neil@email.arizona.edu)
Thu, 24 Jan 2008 09:47:21 -0700
Are there any old timers out there who remember the GDP? We replaced
ours with one donated from the Univ. of Pennsylvania, and now the
"sweet spot" of the lock (the point on the screen where the lock
sweep "wiggles" have to be positioned to get it to lock) has moved
off the right edge of the screen. We can still lock it if we set the
Field to the old value that used to be the center of the screen, but
it's difficult for teaching purposes because they never see the lock signal.
There are two potentiomers in the Lock Board of the GDP, one shown in
the schematics close to the "OFFSET" output and one close to the
"SWEEP" output. Changing the "OFFSET" pot does move the lock display
left and right on the screen, but it also affects the lock amplitude,
and it doesn't get us to the center even when cranked all the way to
one edge of the adjustment. The "SWEEP" pot seems to affect the lock
phase. Are there any other adjustments I can try? I seem to
remember on the old (piano style) AMX consoles an adjustment under
the keyboard, but I can't find anything there in our AM. Is there an
adjustment in the actual lock circuitry (lock receiver?) that would do this?
Any advice would be appreciated. We are running an NMR museum here,
but it just keeps running and the users like it.
Neil
Neil E. Jacobsen, Ph.D.
NMR Facility Manager
Department of Chemistry
119 Old Chemistry
1306 E. University
University of Arizona
Tucson, AZ 85721
520-621-8146
FAX 520-621-8407