Jim T. wrote, in part:
> >The 8k manual also warns not to use the automatic tuner built
> >into many rigs. It sez to leave the auto tuner offline, and
> >just put up with any swr between xcvr and 8k ultra input.
Well, not quite; here is a quote directrly from the Henry 3K/8K
manual I have, Spring 1999:
"Section 7: Maintenance/Troubleshooting
7.2 Input Mismatch
The Ultra series of amplifiers are built with a broadband, unum type
input circuit. The input SWR to the amplifier should always be better
than 2:1. Experience has shown that some transceivers with
automatic tuners have trouble matching this circuit. If you turn off the
tuner, the transceiver should be able to drive the amplifier directly."
> >The VFD wattmeter may be at fault. The henry "input" with
it's
> >back to back un-uns (all relay switched) may be creating some
> >problems.
Yes, as in that what the VFD wattmeter reads is evidently WAY too
high in the power level indicated.
Then Phil C. replied, in part:
> You get what you pay for. The 8-K is rated for 3500 watts PEP MAX.
> No where near 4 kw dissipation......
>The target for the 8-K was an input circuit that will guarantee <2.0-1
>SWR on any frequency from 1.8-30 mhz. with a MAX drive power
>of only 150 watts.
Well, here are the specs directly from the manual, Section 1.
Henry 3K and 8K Ultra Specification:
"Output Power: 3K - 1500 watts PEP or DC nominal.
8K - 5000 watts PEP or 2500 watts DC nominal
Drive Power: 3K - 100 watts, 8K - up to 200 watts nominal.
Duty Cycle: Continuous duty at rated output."
Data supplied with my 8K, taken by Paul Johnson at Henry
shows at a drive power of 200 to as high as 275 watts on
both 160 and 15 meter bands, over 5000 watts of output
power was measured into the big Henry dummy load. Un-
loaded plate voltage was read to be 5800 at that time.
Too 200 watts drive on 20 and 80 to reach such ouput
power, and 230 watts drive on 40, and 250 on 10 to
reach similar output powers. I have never attempted this, hi!!
Don't have a dummy load to take it, and am afraid for my
antenna system components!
Jim T. and Rich M. both point out the need to keep the
filament voltage under control: 7.5 or a bit lower, best.
My mains run closer to 240 out here than 230; thus
my filament voltage, as read on the Controller Unit
meter is more often around 7.6. Guess I better get in there
and move the transformer taps up to the 240 setting from
230, as placed by the factory, per the manual.
Phil also wrote:
>Henry takes care of two problems in the filament circuit with one
>simple part. A power resistor (R617) in the primary of the filament
>transformer limits inrush current and allows setting of the filament
>voltage to the correct value for whatever line voltage that may be
>encountered. A filament voltmeter is included,...
Well, my 1999 manual only shows R617 in the two 3-phase
PS schematics, but NOT in my single phase supply schematic;
wonder why, or if the resistor is actually in the filament supply?
And, R617 is not listed on the separate page which lists the
power supply parts list.
Anyway, very much appreciate the comments by all of you
about the specs and use of this particular Henry amp. Very
pleased with it, and runs just fine for me at amateur legal
levels. Had it on for hours yesterday running CW practice
on both 20 and 40 meters; except I just can't stand to sit
and listen to 5 wpm CW, hi! Believe I am not going to be
doing that speed again. Folks can get their CW up to
at least 10 wpm, then I am going to offer lots of help to
build skill beyond there.
I am not going to worry nor bother anymore about what
the actual input drive power might be; seems to be no
point to it.
73, Jim KH7M
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