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I have been asked to submit the exchange I had with Pete to the
reflector, so here it goes.
Hello, Pete
I'm by no means an expert on the sb-220 amplifier, I'm 16years old and
happen to have one I use on a regular basis contesting and the like. I
have just kept an ear focused on this reflector service for ideas.
However, I wouldn't mind communicating some common problems I have had
with the sb-220 in relation to cooling.
Like I say, I have used the sb-220 in many contesting situations where
the amplifier was running hard for most of the 48 hours, with no
problems, I have never yet had a filament go out during operation, yet I
have had a filament go upon startup, (perhaps an indication that pin
temperature rises too high if the amp is turned off after long stints of
SSB operation?)
When I bought the amp I was reluctant to remain using the limited stock
fan of the sb-220, but being a cheap student I continued until
approximately 6 months ago when I had the failure of the right (viewed
from front) tube's filament. Needless to say I was very worried that I
had lost the tube, but was EXSTATIC to find that the solder on the pin
had melted and dripped out, somehow just enough that the filament would
not light.
I replaced the stock fan with a 6inch tube-axial fan capable of 230CFM
(the stock fan was also 6" in diameter). I was very impressed with the
cooling capability of the fan at 230cfm, I could key down with 1.3KW
output at 2900V full load and it would take a little over 5minutes for
the tubes to show any signs of being hot, mind you the power supply was
humming.
As an aside: I have followed through on Rick Measures (AG6K)'s idea of
overhauling the bleeder resistors on the capacitor bank, with the new
resistors of different value (I forget what they are), the total heat
being dissipated by the bleeders has gone down very noticeably.
However, I still have a small computer CPU fan mounted on standoff's
over the cap-bank that cools that entire area with a little bit of air
flow. This fan may not be needed now as that entire area is dissipating
way less heat.
When I bought the tube-axial fan I knew it was going to be loud and 10x
overkill, but the idea in the end was to build a circuit that could
control the rpm of the fan, thus making it tolerable. However, before I
developed that circuit I had to try the fan out. It proved to be so loud
that during one contest I gave up and placed the amplifier inside an
empty cabinet of an old broadcast transmitter and kept a close eye on
the wattmeter.
After I finished the contest at VE7SCC, I decided that I better start
work on the variable fan rpm idea, for know I have employed a very low
tech solution, I'm using a step down transformer with a few secondary
taps for voltages ranging between 60VAC-90VAC and I can switch them via
an external switch. When running this particular 110VAC tube-axial fan
around 60VAC the noise level is bearable, and the fan still puts out the
air! However, one morning after a long night on 80m, I turned the
amplifier on to chase some gray line dx, and I was shocked to see I had
lost THE SAME FILAMENT yet again. I took the day off school (at the
time it was secondary to this) :)) and I opened the amp to find the
same melted pin. I knew that I had to do something so in the mean time
I decided to solder the pin right to the socket until I could decide
what to do. I managed to entice a good friend of mine, to *donate* a
Johnson 275 socket that would replace the existing socket. The next
week I de-soldered the tube from it's socket and overhauled the entire
affair.
A KEY OBSERVATION WAS NOTED: At the time when I had both the old and
the new sockets sitting on the table I came to the conclusion that the
old socket had lost it's spring tension on the filament pins..!!??? I
researched this on the 'net and found this was a normal occurrence, that
over the years, the heating and cooling will eventually deform the
socket to the point where there is no longer perfect circular contact
between the Johnson 275 filament socket and the tube's filament pin,
thus creating only a few contact points all the way around the pin, this
problem in turn raised the resistance of the connection and therefore
more heat was induced.
I replaced the socket successfully and have been running the amplifier
with the same fan and new socket combination for about 1 year now. In
the last year I have not encountered any problems with that socket,
although I finally had to replace the second one, after it endured the
same situation.
I have opened and seen several other homebrew amplifiers even commercial
amps including Kenwood's TL-992A and noticed one feature that seems to
make sense: This is the fact that Kenwood paints the RF deck close to
the 3-500's BLACK. This makes nothing but sense as black will "suck
away" heat from the envelope of the tube and direct it to the chassis
better then shiny aluminum surfaces will (if I can recall, Rick Measures
points out the same thing on his website, and he recommends taking the
steps to paint that part of the RF-deck black.
Taking his advice, I took it upon myself to paint the RF-deck black.
But before I did this I took a look at the anode while transmitting key
down 1KW+ at HV plate voltage. Looking through the green cover, I got
on the right angle to notice that the side of the anode facing the
aluminum chassis was indeed quite a bit redder in color then the sides
facing the Tank and the blower, This was apparent on both tubes! So the
next weekend I painted that area black, and setup my experiment again.
I now, was not able to detect any "hot spots" on the anode, whether it
was facing the chassis or not, it was all a velvet color! Needless to
say I was pleased.
BOTTOM LINE:
~~~~~~~~~~~~~
I think if you implement the ideas I have described, you will be on your
way to success, the key thing is to catch problems before they arise and
do some preventative maintenance. This is hard for me to do as I rely
solely on the income from cutting neighbor's laws, but for a working
person this would be simple and very cheap for an amp of this
proportion.
A good idea would be to peruse AG6K's site and get an idea for some
improvements you can implement on your SB-220:
http://www.vcnet.com/measures/
~~~~~~~~~~~~~~~~~~~~~~
73 and take it easy,
Ian Procyk,
VE7HHS
-----Original Message-----
From: owner-amps@contesting.com [mailto:owner-amps@contesting.com] On
Behalf Of Pete Smith
Sent: Saturday, October 06, 2001 10:27 PM
To: amps@contesting.com
Subject: [AMPS] SB-220 cooling/filaments
Recently, thinking to help keep my SB-220 cool under contest conditions,
I added a small 110v muffin fan pulling air from the top front of the
tube compartment -- my thought was to enhance the overall flow of
cooling air. The added fan is just sitting on top of the cabinet near
the front edge, and subjective the cabinet does seem to be staying a bit
cooler.
Tonight, when I turned on the amplifier, I see only one filament
lighting. My immediate thought is that I have melted the solder in the
filament pins on that side from excessive heat. Is it plausible that
the "helper" fan could have upset the normal flow sufficiently to have
caused this? Or is it likely just a coincidence?
I will be opening the amp up in the morning, checking for loose socket
pins and DC continuity in the filament -- anything else to look for in
particular?
Thanks...
73, Pete N4ZR
--
FAQ on WWW: http://www.contesting.com/FAQ/amps
Submissions: amps@contesting.com
Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
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<div class=3DSection1>
<p class=3DMsoNormal><font size=3D2 face=3DArial><span =
style=3D'font-size:10.0pt;
font-family:Arial'>I have been asked to submit the exchange I had with =
Pete to
the reflector, so here it goes…<o:p></o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3DArial><span =
style=3D'font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=3DMsoNormal =
style=3D'mso-layout-grid-align:none;text-autospace:none'><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;font-family:"Courier New"'>Hello,
Pete<o:p></o:p></span></font></p>
<p class=3DMsoNormal =
style=3D'mso-layout-grid-align:none;text-autospace:none'><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;font-family:"Courier =
New"'><o:p> </o:p></span></font></p>
<p class=3DMsoNormal =
style=3D'mso-layout-grid-align:none;text-autospace:none'><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;font-family:"Courier New"'>I'm
by no means an expert on the sb-220 <span =
class=3DGramE>amplifier,</span> I'm
16years old and happen to have one I use on a regular basis contesting =
and the
like.<span style=3D'mso-spacerun:yes'> </span>I have just kept an =
ear
focused on this reflector service for ideas.<span
style=3D'mso-spacerun:yes'> </span>However, I wouldn't mind =
communicating
some common problems I have had with the sb-220 in relation to =
cooling.<o:p></o:p></span></font></p>
<p class=3DMsoNormal =
style=3D'mso-layout-grid-align:none;text-autospace:none'><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;font-family:"Courier =
New"'><o:p> </o:p></span></font></p>
<p class=3DMsoNormal =
style=3D'mso-layout-grid-align:none;text-autospace:none'><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;font-family:"Courier New"'>Like
I say, I have used the sb-220 in many contesting situations where the =
amplifier
was running hard for most of the 48 hours, with no problems, I have =
never yet
had a filament go out during operation, yet I have had a filament go =
upon
startup, (perhaps an indication that pin temperature rises too high if =
the amp
is turned off after long stints of SSB operation?)<span
style=3D'mso-spacerun:yes'> </span><o:p></o:p></span></font></p>
<p class=3DMsoNormal =
style=3D'mso-layout-grid-align:none;text-autospace:none'><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;font-family:"Courier =
New"'><o:p> </o:p></span></font></p>
<p class=3DMsoNormal =
style=3D'mso-layout-grid-align:none;text-autospace:none'><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;font-family:"Courier New"'>When
I bought the amp I was reluctant to remain using the limited stock fan =
of the
sb-220, but being a cheap student I continued until approximately<span
style=3D'mso-spacerun:yes'> </span>6 months ago when I had the =
failure of
the right (viewed from front) tube's filament. Needless to say I was =
very
worried that I had lost the tube, but was EXSTATIC to find that the =
solder on
the pin had melted and dripped out, somehow just enough that the =
filament would
not light. <o:p></o:p></span></font></p>
<p class=3DMsoNormal =
style=3D'mso-layout-grid-align:none;text-autospace:none'><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;font-family:"Courier =
New"'><o:p> </o:p></span></font></p>
<p class=3DMsoNormal =
style=3D'mso-layout-grid-align:none;text-autospace:none'><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;font-family:"Courier New"'>I
replaced the stock fan with a 6inch tube-axial fan capable of 230CFM =
(the stock
fan was also 6" in diameter).<span =
style=3D'mso-spacerun:yes'>
</span>I was very impressed with the cooling capability of the fan at =
230cfm, I
could key down with 1.3KW output at 2900V full load and it would take a =
little
over 5minutes for the tubes to show any signs of being hot, mind you the =
power
supply was humming.<span style=3D'mso-spacerun:yes'> =
</span><o:p></o:p></span></font></p>
<p class=3DMsoNormal =
style=3D'mso-layout-grid-align:none;text-autospace:none'><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;font-family:"Courier =
New"'><o:p> </o:p></span></font></p>
<p class=3DMsoNormal =
style=3D'mso-layout-grid-align:none;text-autospace:none'><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;font-family:"Courier New"'>As
an aside: I have followed through on Rick Measures (AG6K)'s idea of =
overhauling
the bleeder resistors on the capacitor bank, with the new resistors of
different value (I forget what they are), the total heat being =
dissipated by
the bleeders has gone down very noticeably.<span
style=3D'mso-spacerun:yes'> </span>However, I still have a small =
computer
CPU fan mounted on standoff's over the cap-bank that cools that entire =
area
with a little bit of air flow. This fan may not be needed now as that =
entire
area is dissipating way less heat.<span =
style=3D'mso-spacerun:yes'> </span><o:p></o:p></span></font></p>
<p class=3DMsoNormal =
style=3D'mso-layout-grid-align:none;text-autospace:none'><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;font-family:"Courier =
New"'><o:p> </o:p></span></font></p>
<p class=3DMsoNormal =
style=3D'mso-layout-grid-align:none;text-autospace:none'><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;font-family:"Courier New"'>When
I bought the tube-axial fan I knew it was going to be loud and <span
class=3DGramE>10x overkill,</span> but the idea in the end was to build =
a circuit
that could control the rpm of the fan, thus making it tolerable.<span
style=3D'mso-spacerun:yes'> </span>However, before I developed =
that circuit
I had to try the fan out. It proved to be so loud that during one =
contest I
gave up and placed the amplifier inside an empty cabinet of an old =
broadcast
transmitter and kept a close eye on the =
wattmeter.<o:p></o:p></span></font></p>
<p class=3DMsoNormal =
style=3D'mso-layout-grid-align:none;text-autospace:none'><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;font-family:"Courier =
New"'><o:p> </o:p></span></font></p>
<p class=3DMsoNormal =
style=3D'mso-layout-grid-align:none;text-autospace:none'><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;font-family:"Courier New"'>After
I finished the contest at VE7SCC, I decided that I better start work on =
the
variable fan rpm idea, for know I have employed a very low tech =
solution, I'm
using a step down transformer with a few secondary taps for voltages =
ranging
between 60VAC-90VAC and I can switch them via an external switch.<span
style=3D'mso-spacerun:yes'> </span>When running this particular =
110VAC
tube-axial fan around 60VAC the noise level is bearable, and the fan =
still puts
out the air!<span style=3D'mso-spacerun:yes'> </span>However, one =
morning
after a long night on 80m, I turned the amplifier on to chase some gray =
line <span
class=3DSpellE><span class=3DGramE>dx</span></span><span =
class=3DGramE>,</span> and I
was shocked to see I had lost THE SAME FILAMENT yet again.<span
style=3D'mso-spacerun:yes'> </span>I took the day off school (at =
the time
it was secondary to this<span class=3DGramE>)<span
style=3D'mso-spacerun:yes'> </span>:</span>)) and I opened the amp =
to find
the same melted pin.<span style=3D'mso-spacerun:yes'> </span>I =
knew that I
had to do something so in the mean time I decided to solder the pin =
right to
the socket until I could decide what to do.<span
style=3D'mso-spacerun:yes'> </span>I managed to entice a good =
friend of
mine, to *donate* a Johnson 275 socket that would replace the existing
socket.<span style=3D'mso-spacerun:yes'> </span>The next week I =
de-soldered
the tube from <span class=3DGramE>it's</span> socket and overhauled the =
entire
affair.<span style=3D'mso-spacerun:yes'> =
</span><o:p></o:p></span></font></p>
<p class=3DMsoNormal =
style=3D'mso-layout-grid-align:none;text-autospace:none'><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;font-family:"Courier =
New"'><o:p> </o:p></span></font></p>
<p class=3DMsoNormal =
style=3D'mso-layout-grid-align:none;text-autospace:none'><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;font-family:"Courier New"'>A
KEY OBSERVATION WAS NOTED:<span style=3D'mso-spacerun:yes'> =
</span>At the
time when I had both the old and the new sockets sitting on the table I =
came to
the conclusion that the old socket had lost it's spring tension on the =
filament
pins..!!??? I researched this on the 'net and found this was a normal
occurrence, that over the years, the heating and cooling will eventually =
deform
the socket to the point where there is no longer perfect circular =
contact
between the Johnson 275 filament socket and the tube's filament pin, =
thus
creating only a few contact points all the way around the pin, this =
problem in
turn raised the resistance of the connection and therefore more heat was
induced. <o:p></o:p></span></font></p>
<p class=3DMsoNormal =
style=3D'mso-layout-grid-align:none;text-autospace:none'><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;font-family:"Courier =
New"'><o:p> </o:p></span></font></p>
<p class=3DMsoNormal =
style=3D'mso-layout-grid-align:none;text-autospace:none'><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;font-family:"Courier New"'>I
replaced the socket successfully and have been running the amplifier =
with the
same fan and new socket combination for about 1 year now.<span
style=3D'mso-spacerun:yes'> </span>In the last year I have not =
encountered
any problems with that socket, although I finally had to replace the =
second
one, after it endured the same situation.<o:p></o:p></span></font></p>
<p class=3DMsoNormal =
style=3D'mso-layout-grid-align:none;text-autospace:none'><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;font-family:"Courier =
New"'><o:p> </o:p></span></font></p>
<p class=3DMsoNormal =
style=3D'mso-layout-grid-align:none;text-autospace:none'><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;font-family:"Courier New"'>I
have opened and seen several other homebrew amplifiers even commercial =
amps
including Kenwood's TL-992A and noticed one feature that seems to make
sense:<span style=3D'mso-spacerun:yes'> </span>This is the fact =
that
Kenwood paints the RF deck close to the 3-500's BLACK.<span
style=3D'mso-spacerun:yes'> </span>This makes nothing but sense as =
black
will "suck away" heat from the envelope of the tube and direct =
it to
the chassis better then shiny aluminum surfaces will (if I can recall, =
Rick
Measures points out the same thing on his website, and he recommends =
taking the
steps to paint that part of the RF-deck black.<span
style=3D'mso-spacerun:yes'> </span><o:p></o:p></span></font></p>
<p class=3DMsoNormal =
style=3D'mso-layout-grid-align:none;text-autospace:none'><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;font-family:"Courier =
New"'><o:p> </o:p></span></font></p>
<p class=3DMsoNormal =
style=3D'mso-layout-grid-align:none;text-autospace:none'><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;font-family:"Courier New"'>Taking
his advice, I took it upon myself to paint the RF-deck black.<span
style=3D'mso-spacerun:yes'> </span>But before I did this I took a =
look at
the anode while transmitting key down 1KW+ at HV plate voltage.<span
style=3D'mso-spacerun:yes'> </span>Looking through the green =
cover, I got
on the right angle to notice that the side of the anode facing the =
aluminum
chassis was indeed quite a bit redder in color then the sides facing the =
Tank
and the blower, This was apparent on both tubes! So the next weekend I =
painted
that area black, and setup my experiment again.<span
style=3D'mso-spacerun:yes'> </span>I now, was not able to detect =
any
"hot spots" on the anode, whether it was facing the chassis or =
not,
it was all a velvet color! Needless to say I was =
pleased.<o:p></o:p></span></font></p>
<p class=3DMsoNormal =
style=3D'mso-layout-grid-align:none;text-autospace:none'><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;font-family:"Courier =
New"'><o:p> </o:p></span></font></p>
<p class=3DMsoNormal =
style=3D'mso-layout-grid-align:none;text-autospace:none'><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;font-family:"Courier =
New"'><o:p> </o:p></span></font></p>
<p class=3DMsoNormal =
style=3D'mso-layout-grid-align:none;text-autospace:none'><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;font-family:"Courier New"'>BOTTOM
LINE:<o:p></o:p></span></font></p>
<p class=3DMsoNormal =
style=3D'mso-layout-grid-align:none;text-autospace:none'><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;font-family:"Courier =
New"'>~~~~~~~~~~~~~<o:p></o:p></span></font></p>
<p class=3DMsoNormal =
style=3D'mso-layout-grid-align:none;text-autospace:none'><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;font-family:"Courier =
New"'><o:p> </o:p></span></font></p>
<p class=3DMsoNormal =
style=3D'mso-layout-grid-align:none;text-autospace:none'><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;font-family:"Courier New"'>I
think if you implement the ideas I have described, you will be on your =
way to
success, the key thing is to catch problems before they arise and do =
some
preventative maintenance.<span style=3D'mso-spacerun:yes'> =
</span>This is
hard for me to do as I rely solely on the income from cutting neighbor's =
laws,
but for a working person this would be simple and very cheap for an amp =
of this
proportion.<o:p></o:p></span></font></p>
<p class=3DMsoNormal =
style=3D'mso-layout-grid-align:none;text-autospace:none'><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;font-family:"Courier =
New"'><o:p> </o:p></span></font></p>
<p class=3DMsoNormal =
style=3D'mso-layout-grid-align:none;text-autospace:none'><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;font-family:"Courier New"'>A
good idea would be to peruse AG6K's site and get an idea for some =
improvements
you can implement on your SB-220:<o:p></o:p></span></font></p>
<p class=3DMsoNormal =
style=3D'mso-layout-grid-align:none;text-autospace:none'><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;font-family:"Courier =
New"'><o:p> </o:p></span></font></p>
<p class=3DMsoNormal =
style=3D'mso-layout-grid-align:none;text-autospace:none'><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;font-family:"Courier New"'><a
href=3D"http://www.vcnet.com/measures/";>http://www.vcnet.com/measures/</a=
><o:p></o:p></span></font></p>
<p class=3DMsoNormal =
style=3D'mso-layout-grid-align:none;text-autospace:none'><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;font-family:"Courier =
New"'><o:p> </o:p></span></font></p>
<p class=3DMsoNormal =
style=3D'mso-layout-grid-align:none;text-autospace:none'><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;font-family:"Courier =
New"'><o:p> </o:p></span></font></p>
<p class=3DMsoNormal =
style=3D'mso-layout-grid-align:none;text-autospace:none'><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;font-family:"Courier =
New"'>~~~~~~~~~~~~~~~~~~~~~~<o:p></o:p></span></font></p>
<p class=3DMsoNormal =
style=3D'mso-layout-grid-align:none;text-autospace:none'><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;font-family:"Courier New"'>73
and take it easy,<o:p></o:p></span></font></p>
<p class=3DMsoNormal =
style=3D'mso-layout-grid-align:none;text-autospace:none'><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;font-family:"Courier New"'>Ian
Procyk,<o:p></o:p></span></font></p>
<p class=3DMsoNormal =
style=3D'mso-layout-grid-align:none;text-autospace:none'><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;font-family:"Courier =
New"'>VE7HHS<o:p></o:p></span></font></p>
<p class=3DMsoNormal =
style=3D'mso-layout-grid-align:none;text-autospace:none'><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;font-family:"Courier =
New"'><o:p> </o:p></span></font></p>
<p class=3DMsoNormal =
style=3D'mso-layout-grid-align:none;text-autospace:none'><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;font-family:"Courier =
New"'><o:p> </o:p></span></font></p>
<p class=3DMsoNormal =
style=3D'mso-layout-grid-align:none;text-autospace:none'><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;font-family:"Courier =
New"'><o:p> </o:p></span></font></p>
<p class=3DMsoNormal =
style=3D'mso-layout-grid-align:none;text-autospace:none'><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;font-family:"Courier New"'>-----Original
Message-----<o:p></o:p></span></font></p>
<p class=3DMsoNormal =
style=3D'mso-layout-grid-align:none;text-autospace:none'><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;font-family:"Courier New"'>From:
owner-amps@contesting.com [<a =
href=3D"mailto:owner-amps@contesting.com";>mailto:owner-amps@contesting.co=
m</a>]
On Behalf <span class=3DGramE>Of</span> Pete =
Smith<o:p></o:p></span></font></p>
<p class=3DMsoNormal =
style=3D'mso-layout-grid-align:none;text-autospace:none'><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;font-family:"Courier New"'>Sent:
Saturday, October 06, 2001 10:27 PM<o:p></o:p></span></font></p>
<p class=3DMsoNormal =
style=3D'mso-layout-grid-align:none;text-autospace:none'><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;font-family:"Courier New"'>To:
amps@contesting.com<o:p></o:p></span></font></p>
<p class=3DMsoNormal =
style=3D'mso-layout-grid-align:none;text-autospace:none'><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;font-family:"Courier New"'>Subject:
[AMPS] SB-220 cooling/filaments<o:p></o:p></span></font></p>
<p class=3DMsoNormal =
style=3D'mso-layout-grid-align:none;text-autospace:none'><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;font-family:"Courier =
New"'><o:p> </o:p></span></font></p>
<p class=3DMsoNormal =
style=3D'mso-layout-grid-align:none;text-autospace:none'><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;font-family:"Courier =
New"'><o:p> </o:p></span></font></p>
<p class=3DMsoNormal =
style=3D'mso-layout-grid-align:none;text-autospace:none'><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;font-family:"Courier New"'>Recently,
thinking to help keep my SB-220 cool under contest conditions, I added a =
small
110v muffin fan pulling air from the top front of the tube compartment =
-- my
thought was to enhance the overall flow of cooling air. The added fan is =
just
sitting on top of the cabinet near the front edge, and subjective the =
cabinet
does seem to be staying a bit cooler.<o:p></o:p></span></font></p>
<p class=3DMsoNormal =
style=3D'mso-layout-grid-align:none;text-autospace:none'><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;font-family:"Courier =
New"'><o:p> </o:p></span></font></p>
<p class=3DMsoNormal =
style=3D'mso-layout-grid-align:none;text-autospace:none'><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;font-family:"Courier New"'>Tonight,
when I turned on the amplifier, I see only one filament lighting. My =
immediate
thought is that I have melted the solder in the filament pins on that =
side from
excessive heat.<span style=3D'mso-spacerun:yes'> </span>Is it =
plausible
that the "helper" fan could have upset the normal flow =
sufficiently
to have caused this?<span style=3D'mso-spacerun:yes'> </span>Or is =
it
likely just a coincidence?<span style=3D'mso-spacerun:yes'> =
</span><o:p></o:p></span></font></p>
<p class=3DMsoNormal =
style=3D'mso-layout-grid-align:none;text-autospace:none'><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;font-family:"Courier =
New"'><o:p> </o:p></span></font></p>
<p class=3DMsoNormal =
style=3D'mso-layout-grid-align:none;text-autospace:none'><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;font-family:"Courier New"'>I
will be opening the amp up in the morning, checking for loose socket =
pins and
DC continuity in the filament -- anything else to look for in =
particular?<o:p></o:p></span></font></p>
<p class=3DMsoNormal =
style=3D'mso-layout-grid-align:none;text-autospace:none'><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;font-family:"Courier =
New"'><o:p> </o:p></span></font></p>
<p class=3DMsoNormal =
style=3D'mso-layout-grid-align:none;text-autospace:none'><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;font-family:"Courier New"'>Thanks...
<o:p></o:p></span></font></p>
<p class=3DMsoNormal =
style=3D'mso-layout-grid-align:none;text-autospace:none'><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;font-family:"Courier =
New"'><o:p> </o:p></span></font></p>
<p class=3DMsoNormal =
style=3D'mso-layout-grid-align:none;text-autospace:none'><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;font-family:"Courier New"'>73,
Pete N4ZR<o:p></o:p></span></font></p>
<p class=3DMsoNormal =
style=3D'mso-layout-grid-align:none;text-autospace:none'><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;font-family:"Courier =
New"'><o:p> </o:p></span></font></p>
<p class=3DMsoNormal =
style=3D'mso-layout-grid-align:none;text-autospace:none'><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;font-family:"Courier =
New"'>--<o:p></o:p></span></font></p>
<p class=3DMsoNormal =
style=3D'mso-layout-grid-align:none;text-autospace:none'><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;font-family:"Courier New"'>FAQ
on WWW:<span
style=3D'mso-spacerun:yes'> &nbs=
p;
</span><a =
href=3D"http://www.contesting.com/FAQ/amps";>http://www.contesting.com/FAQ=
/amps</a><o:p></o:p></span></font></p>
<p class=3DMsoNormal =
style=3D'mso-layout-grid-align:none;text-autospace:none'><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;font-family:"Courier New"'>Submissions:<span
style=3D'mso-spacerun:yes'> &nbs=
p;
</span>amps@contesting.com<o:p></o:p></span></font></p>
<p class=3DMsoNormal =
style=3D'mso-layout-grid-align:none;text-autospace:none'><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;font-family:"Courier New"'>Administrative
requests:<span style=3D'mso-spacerun:yes'>
</span>amps-REQUEST@contesting.com<o:p></o:p></span></font></p>
<p class=3DMsoNormal =
style=3D'mso-layout-grid-align:none;text-autospace:none'><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;font-family:"Courier New"'>Problems:<span
style=3D'mso-spacerun:yes'> &nbs=
p;
</span>owner-amps@contesting.com<o:p></o:p></span></font></p>
<p class=3DMsoNormal =
style=3D'mso-layout-grid-align:none;text-autospace:none'><font
size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;font-family:"Courier =
New"'><o:p> </o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3DArial><span =
style=3D'font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
</div>
</body>
</html>
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--
FAQ on WWW: http://www.contesting.com/FAQ/amps
Submissions: amps@contesting.com
Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
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