DX-100 Followup (60 watts out)

Larry Knapp kc8jx at YAHOO.COM
Mon Dec 1 14:08:11 EST 2003

Wally - It appears you have rectified your output issue OK.  However, I'd like
to take a stab at your comment about "High voltage is running about 650 on the

First I would measure the plate voltage using a reliable volt meter.  I would
rely on the DX-100's metering only after I've proved what is actually occuring
inside the transmitter.  650 volts is too low a value.  The schematic for a
DX-100 or DX-100B shows a plate voltage of at least 750 volts (mine runs more
in the 800 volts range - no load).  The meter of the DX-100 measures this
voltage on one side of a 1 meg resistor, which is off one leg of the 30K (split
15K on each side) power resistor in parallel with the hv capacitors.  I would
personally measure the voltage coming into the capacitors (at the junction of
the 5.5h choke and one of the 125 mfd caps).  This voltage should be approx 740
volts....according to the schematic.  The 740 volts should also appear at the
junction of the 1 meg resistor and one side of the 30K resistor.  If the plate
voltage on the meter appears low....it could be one of two things....the meter
is bad on the Plate Voltage setting (or meter switch is dirty) or the 1 meg
resistor is not really 1 meg anymore....probably higher.

If your still reading low plate voltage on the DX-100's meter, however all
other readings are OK....including your output of about 100 watts, then I'd
suspect the 1 meg resistor.

Hope this helps........best of luck on your DX-100.

73, Larry KC8JX

--- Wally Gibbons <rockwall at SOURCEONEINTERNET.COM> wrote:
> Well, after fiddling with the transmitter for a while, I put my 100 watt
> slug in the Bird wattmeter instead of the 250 watt one. Flipped the
> plate switch, and the DX-100 buried the needle to the right. My 250 watt
> slug is dead, or at least terribly inaccurate. The transmitter runs 100
> watts out with 190ma final current. That's more like it!
> Now to find the best deal on another slug......
> Thanks for the comments!
> Wally Gibbons

************* Waaly Gibbons wrote: *******************************************
Well, I finally got one of these. I've been working through it. Had a
bad 6AQ5, one of the 6146 had a loose (open) plate cap. It's finally
working like I expect with a couple of questions...

60 watts output is it. High voltage is running about 650 on the meter,
and it loads to 250ma easily. But 60 watts is all the Bird will show.
I've tried a new pair of 6146, no improvement. Plenty of grid drive, it
can easily be kept at 5 ma with the drive control. Clamp tube has been
set via the manual. One mod which has been made, it's got a 3 section
365pf each variable cap for the loading cap. No switch or fine loading
control. I'm suspicious of the current reading being off, bad shunt
resistor. Maybe not really running 250 ma? Any DX-100 tips to offer?

Also, with the xtal/vfo switch in the crystal position and no crystals
installed, the 12BY7 plate runs red. It operates zero bias, and with no
crystal no drive so I'd expect it to be warm. But red? As soon as you
switch to VFO it cools right down. Is this a mode to be avoided on the

Thanks, and hope to be on the air with it soon...
And after that, I just picked up a Viking 1.

BA heaven.

Wally Gibbons, WB7ASQ
North Logan, Utah

May your days be full of sunshine and good thoughts fill your head.
From: Larry Knapp, KC8JX, St. Joseph, Mi  49085
  Best 73's

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