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<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Roger, I’m impressed! Thank you for
your concern and persistency in solving problems with your product.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Joy!<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Elwood<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<div>
<p class=MsoNormal><st1:PersonName w:st="on"><font size=2 color=navy
face=Arial><span style='font-size:10.0pt;font-family:Arial;color:navy'>Elwood
Doss</span></font></st1:PersonName><font size=2 color=navy face=Arial><span
style='font-size:10.0pt;font-family:Arial;color:navy'>, Jr., M.M.E., RPT</span></font><font
color=navy><span style='color:navy'><o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Piano Technician/Technical Director</span></font><font
color=navy><span style='color:navy'><o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Department of Music</span></font><font
color=navy><span style='color:navy'><o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>145 Fine Arts Building</span></font><font
color=navy><span style='color:navy'><o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>The <st1:place w:st="on"><st1:PlaceType
w:st="on">University</st1:PlaceType> of <st1:PlaceName w:st="on">Tennessee</st1:PlaceName></st1:place>
at Martin</span></font><font color=navy><span style='color:navy'><o:p></o:p></span></font></p>
<p class=MsoNormal><st1:place w:st="on"><st1:City w:st="on"><font size=2
color=navy face=Arial><span style='font-size:10.0pt;font-family:Arial;
color:navy'>Martin</span></font></st1:City><font size=2 color=navy
face=Arial><span style='font-size:10.0pt;font-family:Arial;color:navy'>, <st1:State
w:st="on">TN</st1:State> <st1:PostalCode w:st="on">38238</st1:PostalCode></span></font></st1:place><font
color=navy><span style='color:navy'><o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>731/881-1852</span></font><font
color=navy><span style='color:navy'><o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>FAX: 731/881-7415</span></font><font
color=navy><span style='color:navy'><o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>HOME: 731/587-5700</span></font><o:p></o:p></p>
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<p class=MsoNormal><b><font size=2 face=Tahoma><span style='font-size:10.0pt;
font-family:Tahoma;font-weight:bold'>From:</span></font></b><font size=2
face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma'>
caut-bounces@ptg.org [mailto:caut-bounces@ptg.org] <b><span style='font-weight:
bold'>On Behalf Of </span></b>Roger Wheelock<br>
<b><span style='font-weight:bold'>Sent:</span></b> Monday, April 28, 2008 7:41
AM<br>
<b><span style='font-weight:bold'>To:</span></b> <st1:PersonName w:st="on">College
and University Technicians</st1:PersonName><br>
<b><span style='font-weight:bold'>Subject:</span></b> [CAUT] yellow light issue
- long post</span></font><o:p></o:p></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
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<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Hello CAUTs,<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Last week piano technician John Ross from <st1:place w:st="on"><st1:City
w:st="on"><u1:place><u1:City>Windsor</st1:City></u1:City>, <st1:State w:st="on"><u1:State>Nova
Scotia</st1:State></st1:place></u1:State></u1:place> provided us with very
useful information that has helped us make progress on solving a minor, but
persistent quality problem associated with the H5 Humidistat in our Piano Life
Saver System. The problem and our current approach to eliminating it are
detailed in the following discussion.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>The challenge with a small percentage of the H5s is that
upon installation, the yellow low water warning light works fine. However,
sometime after installation, the yellow light fails and will not turn on when
the water in the Humidifier is low. Usually, this is discovered by the piano
owner who calls the technician stating one of the following two things, either
“It has been a long time and the yellow light has not come on to tell me
to add water.” Or “the red light is on and the yellow light has
never come on”. The technician makes a service call and finds the tank
nearly dry in the first case and completely dry in the second.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>John encountered this problem, and happened to have two H5
Humidistats in his shop that he could use for the replacement. First, he
decided to test them in his shop and found that one of these failed within the
three hours time. While this frequency of occurrence far exceeds the rate we
have seen in the field, the coincidence was very fortunate as the information
broke a technical impasse we were experiencing in finding the root cause of the
problem.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>John and I talked on the phone at length about the issue.
He has had some experience in electronics prior to becoming a piano
technician. He thought there might be some sort of thermal effect underlying
the problem. He suggested that proximity to a dehumidifier, as in a vertical
installation, might be providing heat to cause the problem. I explained that
we had seen it in grand pianos on occasion, where the Dehumidifiers are much
farther from the Humidistat. The idea of temperature being involved was new
and kept me thinking.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>We set up tests where we sealed the vent holes on the
Humidistats and operated them overnight. Sealing the vent holes allowed for
excessive heat build up inside the Humidistat. The vent holes normally operate
to dissipate heat from the transformer on the circuit board inside the
Humidistat. (The transformer was added to the H5 to meet the increasingly
stringent Underwriter’s Laboratory safety standards for our product.)
However, the inside of the Humidistat does get slightly warmer during
operation. With the vent holes sealed, the inside of the Humidistat reaches a
much higher temperature than during normal operation. Using this procedure we
were able to duplicate the failure in a small number of Humidistats in our
in-house inventory.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>I met with our design engineer, Keith Howell, and our senior
electronics technician, Randy Kaufman on Friday. Under microscopic examination
we had previously observed hairline cracks in a capacitor in the yellow light
circuit in units returned to us from the field. However, the cracks were found
in returns where we could not duplicate the problem as well as in units where
we could. At our meeting on Friday we agreed that the warming of the case
during the first few hours of operation was enough to widen such a crack and
cause the circuit to fail. While this doesn’t tell us what is causing
the crack it gives us an excellent new approach to investigate this more
thoroughly.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Our next steps are as follows. We are testing all
Humidistats under the extreme condition of having the vent holes sealed during
overnight operation. Failures are removed from production and will be closely
analyzed for why they failed. Gayle, our ten-year old son, Robbie and I spent
the weekend testing our entire inventory. Product shipped from our factory as
of Monday, April 28<sup>th</sup> will be free of this defect.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>We will begin testing bare circuit boards while hot to see
if we can reject them prior to assembly. If they fail under these conditions,
it will show that the cracking of the capacitor is being done by our circuit
board supplier. If this is so we will audit their factory to determine where
in their process the problem is caused.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>If it does not appear on the bare boards, we will look even
more closely at our process to see if there is anything we are doing to cause a
physical shock to the circuit board that could create a hairline crack in the
capacitor of concern. We have studied our process closely and do not see
anything of concern. However, the recent thermal hypothesis and the use of
heat in our testing will finally allow us to make a definitive determination
and move forward.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>John has suggested that technicians test Humidistats in
their shops prior to installing the System. This seems like a prudent idea
until old inventory works its way through the distribution system. Simply
place the Humidistat in an upright position (vents facing upward as in normal
installation). Plug in the two-light panel and let the Humidistat run for a
couple hours. Contact us at 800-438-1524 if you encounter a problem and we
will quickly furnish a replacement.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>I am grateful for John’s input to the situation. It
really has made a difference. Thank you, John.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>If any of you have encountered this situation in the field,
I apologize for the frustration you must have experienced. Also if you have a
return that you have not sent back to us, please do. It will help us solve
this permanently at its root cause, rather than eliminating the defect through
testing at the end of our assembly process.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>I welcome your comments, concerns and suggestions. Please
contact me off the list at <a href="mailto:roger@dampp-chaser.com">roger@dampp-chaser.com</a>.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Sincerely,<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Roger Wheelock, VP<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Dampp-Chaser Corporation<o:p></o:p></span></font></p>
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