<html>
<head>
<meta content="text/html; charset=ISO-8859-1"
http-equiv="Content-Type">
</head>
<body bgcolor="#FFFFFF" text="#000000">
Nice catch indeed!<br>
<br>
<div class="moz-cite-prefix">On 03/06/2014 03:00 PM, Richard Jones
wrote:<br>
</div>
<blockquote
cite="mid:CABfxa3Tma69fRCfpy5=PDDdY59wDP9e4AdRnMR=YwVG76UkY0g@mail.gmail.com"
type="cite">
<div dir="ltr">Dear colleagues,
<div><br>
</div>
<div>Kudos to Alex Barnes, who has been struggling for almost
two weeks now to understand the reason why our preamplifier
boards have an ugly oscillation in the signal baseline at 100
kHz, as soon as we set them up and bias them for readout of
fibers. We traced the problem down to one malfunctioning
component which is a voltage regulator on the preamp board
that generates one of the critical dc voltages for the
amplifier. That part was generating 100kHz oscillations on
our board, but they would go away under certain weird
conditions, which are not compatible with actual running,
unfortunately. Chasing down the particulars of those weird
conditions turned out to be a red herring.</div>
<div><br>
</div>
<div>Finally Alex decided that either all of the parts are
burned out and malfunctioning in the same way on all of the
boards, or else it is actually the wrong part that was
installed by the manufacturer. The second turned out to be
correct. We ordered some of the correct part ourselves from
Digikey and swapped it out, and voila the oscillations are
gone. After extensive searching online, we have determined
that the manufacturer installed the TLV431BSNT1G instead of
the NCP100SNT1G that we specified in our parts list. This is
confirmed both by the markings on the chip and by the
operating characteristics. Both of these are shunt regulators,
but they have reference voltages that are different by almost
a factor 2. Now that it is understood, we are back on track
with setting up for QA of fibers.</div>
<div><br>
</div>
<div>-Richard Jones</div>
</div>
<br>
<fieldset class="mimeAttachmentHeader"></fieldset>
<br>
<pre wrap="">_______________________________________________
Halld-tagger mailing list
<a class="moz-txt-link-abbreviated" href="mailto:Halld-tagger@jlab.org">Halld-tagger@jlab.org</a>
<a class="moz-txt-link-freetext" href="https://mailman.jlab.org/mailman/listinfo/halld-tagger">https://mailman.jlab.org/mailman/listinfo/halld-tagger</a></pre>
</blockquote>
<br>
<pre class="moz-signature" cols="72">--
Mark M. Ito, Jefferson Lab, <a class="moz-txt-link-abbreviated" href="mailto:marki@jlab.org">marki@jlab.org</a>, (757)269-5295
</pre>
</body>
</html>