[Heathkit] DX-40 question

[Bwana Bob]

I wouldn't try it without a crystal.  If it's anything like my DX-60A, 
the bias is dependent on having adequate grid drive to the final. 
Without a crystal or VFO, the plate current will be excessive and either 
burn out the cathode resistor or the final tube.

73,

Bob WB2VUF


On 9/25/2016 3:27 PM, Bill Cromwell wrote:
> Hi,
>
> He did say it will take off without even having an xtal in the socket. 
> That seems like feedback from the final to it's own input or to the 
> prior stage. And what about the screen bypass?
>
> 73,
>
> Bill  KU8H
>
> On 09/25/2016 11:45 AM, Buck via Heathkit wrote:
>> Jack,
>>
>> Not familiar with issue, but I assume you've tried a couple xtals?
>>
>>
>>
>>
>>
>> On Sunday, September 25, 2016 Jack Antonio <scr287 at att.net> 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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