[AMPS] Adjusting fil voltage
Radiodan W7RF
RFpower@radiodan.com
Tue, 19 Jan 1999 15:56:30 -0800
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Simple yet so valuable, this information. This is the opposite of the guys
who want to squeak just 50 watts more by using a variac on both HV and
filament to RAISE the voltage!
Controlling filament voltage (via the primary) is a worthwhile endeavor. It
could make your tubes into "lifetime" tubes.
I can't imagine why anyone would do this in the secondary?
I used this method (primary) with a 25 ohm 50 watt wirewound reostat in the
primary of my old Henry 4K to lower the filament voltage on an expensive
5CX1500A tube.
Actual numerical voltage value is not that important, I just turned it down
to where power output dropped off and went back up about .1 or .2 volts
(reading secondard voltage).
This also acts as an inrush current limiter as a bonus.
73, Dan Magro W7RF, (President WARC 1999, member SCDXC, SCCC)
Manufacturers Rep & Distributor for HENRY Amplifiers.
www.radiodan.com RFpower@radiodan.com
A trip to our web site is worth the click!
-----Original Message-----
From: owner-amps@contesting.com [mailto:owner-amps@contesting.com]On
Behalf Of Roy Koeppe
Sent: Tuesday, January 19, 1999 11:25 AM
To: amps@contesting.com
Subject: [AMPS] Adjusting fil voltage
Measures, Orr, et al have presented excellent information concerning the
great importance of correct PA fil voltage. Being mostly a CW op, my current
peaks are much lower than those in SSB mode. Therefore, I have lowered the
fil voltage on my pair of 3-500Zs the recommended amount, and they have
rewarded me with faithful, extended service life.
However, the methods proposed in these discussions are rather extreme or
awkward. My method is simply to install the dropping resistor in the fil
xfmr primary, instead of the more critical secondary. It does require that
your amp has a separate fil xfmr of course. The values needed for primary
resistors are very much more commonplace than those in the secondary.
When measuring fil voltage it is important to use the proper type of
meter. The waveshape is often distorted enough so that it becomes a
consideration how your meter responds to the average voltage. The very best
type is the iron vane AC meter. These are sometimes available used from
industrial sources. I have used iron vanes with mirrored scales, and some
have typical accuracies of 0.1 percent at 3/4 scale. Iron vane AC meters
inherently average waveform distortion to a near perfect degree. Anyway,
keep an eye out for them.
73, K6XK/0
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<META content=3Dtext/html;charset=3Diso-8859-1 =
http-equiv=3DContent-Type>
<META content=3D'"MSHTML 5.00.0910.1309"' name=3DGENERATOR></HEAD>
<BODY bgColor=3D#ffffff>
<DIV><FONT color=3D#0000ff face=3D"Comic Sans MS" size=3D2>
<DIV><SPAN class=3D920395019-19011999><FONT color=3D#0000ff =
face=3D"Comic Sans MS"=20
size=3D2>Simple yet so valuable, this information. This is the opposite =
of the=20
guys who want to squeak just 50 watts more by using a variac on both HV =
and=20
filament to RAISE the voltage! </FONT></SPAN></DIV>
<DIV><SPAN class=3D920395019-19011999><FONT color=3D#0000ff =
face=3D"Comic Sans MS"=20
size=3D2>Controlling filament voltage (via the primary) is a worthwhile =
endeavor.=20
It could make your tubes into "lifetime" =
tubes.</FONT></SPAN></DIV>
<DIV> </DIV>
<DIV><SPAN class=3D920395019-19011999><FONT color=3D#0000ff =
face=3D"Comic Sans MS"=20
size=3D2>I can't imagine why anyone would do this in the=20
secondary?</FONT></SPAN></DIV>
<DIV> </DIV>
<DIV><SPAN class=3D920395019-19011999><FONT color=3D#0000ff =
face=3D"Comic Sans MS"=20
size=3D2>I used this method (primary) with a 25 ohm 50 watt wirewound =
reostat in=20
the primary of my old Henry 4K to lower the filament voltage on an =
expensive=20
5CX1500A tube.</FONT></SPAN></DIV>
<DIV><SPAN class=3D920395019-19011999><FONT color=3D#0000ff =
face=3D"Comic Sans MS"=20
size=3D2>Actual numerical voltage value is not that important, I just =
turned it=20
down to where power output dropped off and went back up about .1 or .2 =
volts=20
(reading secondard voltage).</FONT></SPAN></DIV>
<DIV><SPAN class=3D920395019-19011999><FONT color=3D#0000ff =
face=3D"Comic Sans MS"=20
size=3D2>This also acts as an inrush current limiter as a=20
bonus.</FONT></SPAN></FONT></DIV></DIV>
<P><FONT face=3D"Comic Sans MS"><FONT size=3D3>73, Dan Magro <FONT=20
face=3D"Comic Sans MS">W7RF, (President WARC 1999, member <FONT =
color=3D#000000=20
face=3D"">SCDXC, SCCC</FONT>)<BR>Manufacturers Rep & Distributor for =
HENRY=20
Amplifiers.<BR></FONT></FONT></FONT><FONT size=3D3><FONT face=3D"Comic =
Sans MS"><A=20
href=3D"http://www.radiodan.com"=20
target=3D_blank>www.radiodan.com</A> <A=20
href=3D"mailto:RFpower@radiodan.com">RFpower@radiodan.com<BR></A></FONT><=
FONT=20
face=3D"Comic Sans MS">A trip to our web site is worth the=20
click!<BR></FONT></FONT></P>
<DIV> </DIV>
<BLOCKQUOTE=20
style=3D"BORDER-LEFT: #0000ff 2px solid; MARGIN-LEFT: 5px; MARGIN-RIGHT: =
0px; PADDING-LEFT: 5px">
<DIV class=3DOutlookMessageHeader><FONT face=3D"Times New Roman"=20
size=3D2>-----Original Message-----<BR><B>From:</B> <A=20
=
href=3D"mailto:owner-amps@contesting.com">owner-amps@contesting.com</A> =
[<A=20
=
href=3D"mailto:owner-amps@contesting.com">mailto:owner-amps@contesting.co=
m</A>]<B>On=20
Behalf Of</B> Roy Koeppe<BR><B>Sent:</B> Tuesday, January 19, 1999 =
11:25=20
AM<BR><B>To:</B> <A=20
=
href=3D"mailto:amps@contesting.com">amps@contesting.com</A><BR><B>Subject=
:</B>=20
[AMPS] Adjusting fil voltage<BR><BR></FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2>Measures, Orr, et al have =
presented excellent=20
information concerning the great importance of correct PA fil voltage. =
Being=20
mostly a CW op, my current peaks are much lower than those in SSB =
mode.=20
Therefore, I have lowered the fil voltage on my pair of 3-500Zs the=20
recommended amount, and they have rewarded me with faithful, extended =
service=20
life.</FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2></FONT> </DIV>
<DIV><FONT color=3D#000000 size=3D2>However, the methods proposed in =
these=20
discussions are rather extreme or awkward. My method is simply =
to=20
install the dropping resistor in the fil xfmr primary, instead of the =
more=20
critical secondary. It does require that your amp has a separate fil =
xfmr of=20
course. The values needed for primary resistors are very much more =
commonplace=20
than those in the secondary.</FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2></FONT> </DIV>
<DIV><FONT color=3D#000000 size=3D2>When measuring fil voltage it is =
important to=20
use the proper type of meter. The waveshape is often distorted enough =
so that=20
it becomes a consideration how your meter responds to the average =
voltage. The=20
very best type is the iron vane AC meter. These are sometimes =
available used=20
from industrial sources. I have used iron vanes with mirrored scales, =
and=20
some have typical accuracies of 0.1 percent at 3/4 scale. =
Iron=20
vane AC meters inherently average waveform distortion to a near =
perfect=20
degree. Anyway, keep an eye out for them.</FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2></FONT> </DIV>
<DIV><FONT color=3D#000000 size=3D2>73, =20
K6XK/0 </FONT></DIV></BLOCKQUOTE></BODY></HTML>
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