[Heathkit] DX-40 question

[Bill Cromwell]

Hello Jack,

I don't have a DX 40. For the Johnson Ranger the issues is usually 
resolved by good grounding of the shield. Make sure *all* of the ground 
contact area (including under the spade lugs) id clean. Some owners have 
added heavy aluminum foil and metal foil tape along the seams. I have 
the hulk of a DX-35 here and that shield looks inadequate to me. 
Cleaning up the grounding contact area ofr the (much bigger) shield in 
my Ranger cleared the instability problems I was having. The added foil 
tape was insufficient in my radio.

On the Rangers there is a pair of metal shafts that are coupled by an 
insulating sleeve to bring one of the tuning cap controls to the front 
panel. If those touch inside that sleeve they 'can' provide a feedback 
path for the instability you describe. This hasn't made any difference 
in my Ranger and may not apply to the DX-40 at all.

Best of luck getting your radio working.

73,

Bill  KU8H

On 09/25/2016 10:39 AM, Jack Antonio wrote:
> I'm working on the same DX-40 I've had since my Novice
> days 50 some years ago.
>
> Cleaning, tightening screws, checking solder joints
> new 6146, tune up.
>
> And the end result is a transmitter that works good
> with one exception.
>
> It is a little squirrely on 40 meters, with 40 meter
> crystals. The "band-aid" is to back the oscillator coil all the
> way out, and keep grid drive below 2mA.
>
> By squirrely, I mean that it has a tendency to take off
> on its own without a crystal in the socket, jumpy tuning,
> sluggish crystal activity that depends on both tuning and
> the position of the meter switch. Again, this is only
> on 40, with 40 meter crystals. All other bands work just fine.
>
> The question is, wasn't this documented somewhere? I seem
> to recall this, but a search of the ARRL QST archive, and
> a quick look through my 73 magazines, didn't reveal anything.
>
> Just wondering if anyone else has heard of this, or know of
> any writeups about it.
>
> Thing is, I don't remember this issue from 50 years ago, but
> then also, I never had good luck with this transmitter on 40.
> Always had good results on 80 and 15 though.
>
> Thanks
>
> Jack Antonio WA7DIA/4
>
>
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