[Heathkit] DX-100B - spurs everywhere.

[Carl]

Check the value of the parasitic suppressor resistors.

Carl
KM1H


----- Original Message ----- 
From: "Rick Poole" <wa1rkt at arrl.net>
To: <heathkit at mailman.qth.net>
Sent: Thursday, December 01, 2011 9:22 PM
Subject: Re: [Heathkit] DX-100B - spurs everywhere.


>
> A couple of people told me that the oscillations I was seeing on
> phone were likely neutralization, and one person told me that
> "Neutralization can be done in several well-documented ways".
>
> So, I went searching and found a few...
>
> http://home.roadrunner.com/~boatanchors1/dx-100%20neut.html
> http://home.roadrunner.com/~boatanchors1/posting.html
> http://groups.yahoo.com/group/heathkit/message/19871
>
> ... not much of anything else.
>
> So, I tried adjusting the little wire that pokes into the PA
> compartment and managed some pretty dramatic results... now I get
> spurs on both AM and CW and they are quite readily generated.
>
> Put the neutralization wire back where it was, no real
> improvement.  There is no position of the neutralization wire that
> shows any significant difference in behavior.
>
> I think it always did this on CW, I just had to get the plate farther
> out of resonance on the high side before it would do it.  I can still
> tune the rig on CW and it will be stable, but I have to be careful
> not to get out of resonance on the high side (AMPLIFIER pointer
> points to higher numbers; plate tuning cap is more meshed).
>
> One thing I noticed... one of the articles on neutralization
> emphasized keeping the grid current around 4 ma, and the DX-100
> manual cautions against running the grid current above 6 ma and
> recommends keeping it at around 5 ma.  My grid current will not go
> above about 2.5 ma no matter what, at least not on 80 meters (haven't
> tried any other bands yet).  And yet, when it is stable and putting
> out the correct frequency, I can easily get between 100 and 125 watts
> out at a plate current of 200-250 ma, just like the book says.  So I
> can't figure out why the grid current is so low.
>
> Next step is to check all the tubes in the tube tester, and then
> wrestle the thing over to the workbench and start loosening and
> retightening hardware and checking resistor values (don't have a way
> of checking capacitor values yet).
>
> Anybody have an idea off the top of their heads why the grid current is so 
> low?
>
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