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Over the weekend I had an opportunity to work on a Henry 2K Classic. =
This is a beautiful 120 pound console amplifier using 2 x 3-500Z tubes.
After repairing some problems and getting it working, I measured the =
filament voltage at the socket. It was 5.62 volts with 252 vac line =
voltage. I noted that there was a special "surge" inductor under the =
chassis for the filament already. Filament volts at the transformer was =
12.05 volts - feeding the 2 tubes filaments in series. I reduced the =
voltage by installing 2 x .1 ohm 10 watt resistors in parallel at the =
transformer.
After all work was done, 70 watts drive produced 1,000 watts out on high =
power - which is exactly the same power I measured 2 days earlier on the =
55 pound (or so) Heath SB-220 on high power with the same drive. =20
The Henry is a beautiful amplifier that uses no variable plate tuning =
capacitor. Instead, it uses fixed, switched capacitors and tunes with a =
variable inductor. Although it is very nice, it is probably the slowest =
amp to QSY of any commercial amp I have ever used and would be a =
horrible contest amp. It may even be slower than my home brew 4-1000 =
amplifiers. =20
Looking at the construction of both the Henry and the Heath, I am =
impressed that the "puny" Heath puts out as much power as the Henry. It =
is a tribute to the design skills of the Heath engineers. =20
73, Colin K7FM
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<DIV><FONT face=3DArial size=3D2>Over the weekend I had an opportunity =
to work on a=20
Henry 2K Classic. This is a beautiful 120 pound console amplifier =
using 2=20
x 3-500Z tubes.</FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=3DArial size=3D2>After repairing some problems and =
getting it=20
working, I measured the filament voltage at the socket. It was =
5.62 volts=20
with 252 vac line voltage. I noted that there was a special =
"surge"=20
inductor under the chassis for the filament already. Filament =
volts at the=20
transformer was 12.05 volts - feeding the 2 tubes filaments in =
series. I=20
reduced the voltage by installing 2 x .1 ohm 10 watt resistors in =
parallel at=20
the transformer.</FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=3DArial size=3D2>After all work was done, 70 watts drive =
produced=20
1,000 watts out on high power - which is exactly the same power I =
measured 2=20
days earlier on the 55 pound (or so) Heath SB-220 on high power with the =
same=20
drive. </FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=3DArial size=3D2>The Henry is a beautiful amplifier that =
uses no=20
variable plate tuning capacitor. Instead, it uses fixed, switched=20
capacitors and tunes with a variable inductor. Although it is very =
nice,=20
it is probably the slowest amp to QSY of any commercial amp I have ever =
used and=20
would be a horrible contest amp. It may even be slower than my =
home brew=20
4-1000 amplifiers. </FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=3DArial size=3D2>Looking at the construction of both the =
Henry and=20
the Heath, I am impressed that the "puny" Heath puts out as much power =
as the=20
Henry. It is a tribute to the design skills of the Heath =
engineers. =20
</FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=3DArial size=3D2>73, Colin =20
K7FM</FONT></DIV></BODY></HTML>
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