[AMPS] 6 volts on a 3-500Z filament

Colin Lamb k7fm@teleport.com
Mon, 6 Mar 2000 13:04:06 -0800


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It has been noted that some Henry amplifiers run 6 volts on the filament =
of 3-500Z tubes.  This also has been noted as the reason for including =
rheostats in the filament supply of commercial rigs.

6 volts on a 5 volt tube is obviously not acceptable.  Assuming an =
amplifier was built for 115/230 service,  the filament voltage with the =
more normal 120/240 service would still be within manufacturer =
specifications.  If the filament voltage is 6 volts when the mains =
voltage is within manufacturer specifications, then the amplifier is =
defective and not merchantable.  Section 2.3140 (Implied Warranty of =
Merchantability) of the Uniform Commercial Code has been adopted in all =
50 states and gives the purchaser certain rights.  In addition most =
states have adopted other and additional consumer laws.  Anyone who =
purchases an amplifier knowing that 6 volts are used on a 5 volt =
filament is simply stupid and deserves what he gets.  If he does not =
know it when he purchases, he can take it back and get a refund.   =20

Otherwise, if the amplifier is designed and operating properly, the =
normal variation of line voltage will still be within the + or - 10% =
variation specified by the tube manufacturer.  If your line voltage =
exceeds normal, a variac can be purchased and used on the primary. =20

I have a number of commercial amplifiers used with my 122/244 line =
voltage.  All amplifiers are within spec on filament voltage except for =
one - and I simply installed a fixed resistor in series with the =
filament.  The only commercial rig I ever had with a filament adjustment =
was the Collins KWS-1 - yet in 44 years of operating I have never lost =
an amplifier tube filament.  I expect that 99% of tube flattening is =
caused by operator abuse and 1% by filament overvoltage.  This ignores =
those amplifiers which use 6 volts on a 5 volt filament because they are =
defective and merit no further discussion. =20

Colin  K7FM=20

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<DIV><FONT face=3DArial size=3D2>It has been noted that some Henry =
amplifiers run 6=20
volts on the filament of 3-500Z tubes.&nbsp; This also has been noted as =
the=20
reason for including rheostats in the filament supply of commercial=20
rigs.</FONT></DIV>
<DIV>&nbsp;</DIV>
<DIV><FONT face=3DArial size=3D2>6 volts on a 5 volt tube is obviously =
not=20
acceptable.&nbsp; Assuming&nbsp;an amplifier was built for 115/230=20
service,&nbsp; the filament voltage with the more normal 120/240 service =
would=20
still be within manufacturer specifications.&nbsp; If the filament =
voltage is 6=20
volts when the&nbsp;mains voltage is within manufacturer specifications, =
then=20
the amplifier is defective and not merchantable.&nbsp; Section 2.3140 =
(Implied=20
Warranty of Merchantability) of the Uniform Commercial Code has been =
adopted in=20
all 50 states and gives the purchaser certain rights.&nbsp; In addition =
most=20
states have adopted other and additional consumer laws.&nbsp; Anyone who =

purchases an amplifier knowing that 6 volts are used on a 5 volt =
filament is=20
simply stupid and deserves what he gets.&nbsp; If he does not know it =
when he=20
purchases, he can take it back and get a refund.&nbsp; &nbsp; =
</FONT></DIV>
<DIV>&nbsp;</DIV>
<DIV><FONT face=3DArial size=3D2>Otherwise, if the amplifier is designed =
and=20
operating properly, the normal variation of line voltage will still be =
within=20
the + or - 10% variation specified by the tube manufacturer.&nbsp; If =
your line=20
voltage exceeds normal, a variac can be purchased and used on the =
primary.&nbsp;=20
</FONT></DIV>
<DIV>&nbsp;</DIV>
<DIV><FONT face=3DArial size=3D2>I have a number of commercial =
amplifiers used with=20
my 122/244 line voltage.&nbsp; All amplifiers are within spec on =
filament=20
voltage except for one - and I simply installed a fixed resistor in =
series with=20
the filament.&nbsp; The only commercial rig I ever had with a filament=20
adjustment was the Collins KWS-1 - yet in 44 years of operating I have =
never=20
lost an amplifier tube filament.&nbsp; I expect&nbsp;that 99% of tube =
flattening=20
is caused by operator abuse and 1% by filament overvoltage.&nbsp;=20
This&nbsp;ignores those amplifiers which use 6 volts on a 5 volt =
filament=20
because they are defective and merit no further=20
discussion.&nbsp;&nbsp;</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT face=3DArial size=3D2>Colin&nbsp; =
K7FM</FONT>&nbsp;</DIV></BODY></HTML>

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