[AMRadio] DX-100

Jim Wilhite w5jo at brightok.net
Sun Jul 18 17:18:35 EDT 2004

I had similar problems and it turned out to be the 12BY7 tube socket.  It
had been in a barn for a number of years.  The grid pin of the 12BY7 was
corroded even though I sprayed it with DeOxit and worked it in and out
several times.  I finally found it with a tube extender.  Also the input
cap. in the low high voltage circuit (the one before the choke) had lost
capacitance resulting in low voltage readings on the first two tubes in the

Put it in the CW position and tune the grid knob for the reading you want,
that way you won't have to have the HV on all time.  The keying circuit may
have problems as well causing what you describe.  Check the drive pot for
opens with your ohm meter.  If the ohm meter does not show a smooth
movement, then replace the pot.  Digikey and Mouser have them.

If I can help any more, let me know.

73  Jim
de W5JO

----- Original Message ----- 
From: "Gary Poland" <gpoland1 at cinci.rr.com>
To: "Discussion of AM Radio" <amradio at mailman.qth.net>
Sent: Sunday, July 18, 2004 2:00 PM
Subject: Re: [AMRadio] DX-100

> Jim,
>   My first experience with the DX-100...looking at it for a friend. It has
> had some fingers in it. The drive control has to be almost full CW before
> get any grid current then its way high and I have to set the drive control
> back to a normal position for the 5 ma. The driver stage is very touchy
> the output erratic. Any thing you have would be great.
> 73, Gary
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