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I would guess that the sb200 isn't the only one to suffer hi fil. volts. =
almost any amp designed in the 50's/60's and 70's likely have that =
problem because the ac line standard back then was about 115 volts. =
today's standard is closer to 125, about a 10% increase. if you increase =
6.3 volts by 10% you have about 6.9volts and thats only approximate =
since my line voltage often gets up to 130. I think that even today =
many "modern" amps come out with hi fil.voltages, from what I've been =
hearing and reading on this reflector at times.That doesn't help the =
life of some very expensive tubes!!!!! just my $.02 worth!!
carl / kz5ca
----- Original Message -----=20
From: KG6DV@cs.com=20
To: amps@contesting.com=20
Sent: Wednesday, November 07, 2001 6:51 AM
Subject: [AMPS] SB200 Filament Voltage
I found a very clean SB200 I couldnt resist. While checking this amp =
out I found an interesting situation, High filament voltage. The SB200 =
has no separate filament transformer. It uses one transformer with three =
secondary windings. I have always put filament variacs in all my =
homebrew amps but they all had separate filament transformers. The =
filament voltage on this amp measures 7.25 volts vs the 6.3 volts =
required by the 572B'S. Considering the fact that this about 15% =
higher than specs, Im not comfortable leaving it that way. Is this a =
common problem with the SB200'S ?=20
Any suggestions on how to correct the problem?=20
Ron KH6DV=20
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<DIV><FONT face=3DArial size=3D2>I would guess that the sb200 isn't the =
only one to=20
suffer hi fil. volts. almost any amp designed in the 50's/60's and 70's =
likely=20
have that problem because the ac line standard back then was about 115 =
volts.=20
today's standard is closer to 125, about a 10% increase. if you increase =
6.3=20
volts by 10% you have about 6.9volts and thats only approximate since =
my =20
line voltage often gets up to 130. I think that even today many "modern" =
amps=20
come out with hi fil.voltages, from what I've been hearing and reading =
on this=20
reflector at times.That doesn't help the life of some very expensive =
tubes!!!!!=20
just my $.02 worth!!</FONT></DIV>
<DIV><FONT face=3DArial size=3D2> carl / kz5ca</FONT></DIV>
<BLOCKQUOTE=20
style=3D"PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; =
BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
<DIV style=3D"FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV=20
style=3D"BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: =
black"><B>From:</B>=20
<A title=3DKG6DV@cs.com href=3D"mailto:KG6DV@cs.com";>KG6DV@cs.com</A> =
</DIV>
<DIV style=3D"FONT: 10pt arial"><B>To:</B> <A =
title=3Damps@contesting.com=20
href=3D"mailto:amps@contesting.com";>amps@contesting.com</A> </DIV>
<DIV style=3D"FONT: 10pt arial"><B>Sent:</B> Wednesday, November 07, =
2001 6:51=20
AM</DIV>
<DIV style=3D"FONT: 10pt arial"><B>Subject:</B> [AMPS] SB200 Filament=20
Voltage</DIV>
<DIV><BR></DIV><FONT face=3Darial,helvetica><FONT size=3D2>I found a =
very clean=20
SB200 I couldnt resist. While checking this amp out I found an=20
interesting situation, High filament voltage. The SB200 has no =
separate=20
filament transformer. It uses one transformer with three secondary =
windings. I=20
have always put filament variacs in all my homebrew amps but they all =
had=20
separate filament transformers. The filament voltage on this amp =
measures 7.25 volts vs the 6.3 volts required by the 572B'S. =
Considering=20
the fact that this about 15% higher than specs, Im not =
comfortable=20
leaving it that way. Is this a common problem with the SB200'S ? =
<BR>Any=20
suggestions on how to correct the problem? <BR><BR>Ron KH6DV=20
<BR></BLOCKQUOTE></FONT></FONT></BODY></HTML>
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