AMMRL: ASX troubleshooting

Karen Ann Smith (karenann@unm.edu)
Tue, 11 Dec 2007 12:03:34 -0700 

ammrlers;

The proton channel of our ASX died. Bruker has been helping us 
troubleshoot, but we have all run out of ideas.  Details are below, we 
welcome any thoughts or suggestions. (Except to get a new console- much 
as I would love one, I don't think Santa will be leaving one under the 
tree.)

In addition, does anyone have:

1) Schematics that show how the hpcu connects to the hpcu keyboard.  We 
have the manual for the hpcu, but it doesn't have schematics.

2) Schematics for the backplane of the se451.  We have the se451 book, 
which contains schematics for the individual modules (tfx, tfh, lo, and 
rft) but it does not have anything on the motherboard/backplane.

Symptoms of our problem:

The output of the se451 proton channel is 400mv of messy 100 MHz
pulsed, when it should be 800 mv of clean 300, pulsed and phased.  It is
unknown if the 100 is phased correctly.

Wobble for proton is bad. This is because the wobble frequency is 100 MHz.

The proton pulse lights on the hpcu keyboard will flash once and not
again.  This may or may not relate to the major problem.

Note that X works fine.  800mv of clean out of the se451, wobble works, 
and the hpcu pulse lights work. (And, we can get data.)

Tried:

  1) The pts should put out 140 MHz, 10 MHz, and whatever the X channel
is requesting.  It does.  In addition, the pts was swapped, and the
proton module inside was swapped. No change in symptoms.

  2) The hpcu and 4 phase modulator were swapped.  No change.

  3) The 100 MHz output of the se451 was measured on the board,
at the burndy connector (with the breakout box), and at the input to the
blt4s.  Signal was measured both teed off to the scope and directly to
the scope.  Signal was the same everywhere.

  4) The se451 was swapped several times, as was the proton module.  No
change.

  5) The inputs to the tfh/se451 look fine.  The 9 and 19 volts look
clean on a scope (j, k, and y) .  The pulse marker (f) is above 1 V and
clean.  The 140 MHz (b) is 800 mv and clean.

  6) Looking at the test point on the tfh board, the correct 140 MHz is 
seen.

  7) Looking at the other test point, which should show 300 (or maybe
100) MHz, nothing is seen.  The same test point on the tfx board also
shows no signal, so this may not be a real problem.

  8)  Looking at POH and POX, they both are 100 mv of 891 (measured on a
350 MHz scope).  Swapping the cables from the lo to the tfh and tfx
changed nothing.

9) While the problem was originally seen in solids mode, most of the 
troubleshooting has been in solution mode. So, that does not appear 
relevant.

thanks,

kas
-- 
Karen Ann Smith                karenann@unm.edu
Director, NMR Facility         Adj. Asst. Prof.
Dept. of Chemistry             Clark Hall  MSC03 2060
University of New Mexico       Albuquerque, NM 87131-0001
505.277.4031                   url: http://www.unm.edu/~karenann
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