[AMRadio] DX-100B Low Output on 15/10 Meters - Update

Geoff/W5OMR w5omr at w5omr.shacknet.nu
Mon Oct 25 20:46:51 EDT 2004

> Any comments as to why I saw the drop off in power when the signal was
> modulated?  If anything, I expected to find a soft rectifier tube.  Also,
> the drop in Ip and Ep associated with the drop in power was about 20 mA and
> 20V respectively; certainly not enough to account for a 40W drop in output
> power!

It's been too long since I had my fingers on a DX a'hunnert, Mark...  but if
anything like the Johnson equipment, you probably need to pay special attention
to the Oscillator and Buffer stages, which affect grid drive.  These stages can
mis-tuned, causing an unwanted situation in the control grids of the 6146
which are common in both rigs.

No more than 5mA of Ig is recommended on a pair of 6146's.  Johnson even
had a 'red-line' in some of their equipment, to indicate that grid drive should
'no more than this level'.

Another cause of final instability, would be neutralization of the push-pull
A most picky and delicate thing, the higher in frequency you operate.  Not so
critical on lower frequencies.

Perhaps these ideas might help your situation... I don't remember seeing the
original message.

I remember my dad telling the story of how Lee/K5HZR, back when he was
one of the Net Control operators of the 7.290 traffic net, here in the 5th call
region.  Seems that Lee also had a Heatkit "Benton Harbor kiloWatt"
(DX-100) and he wore out three different meter switches, always checking
everything possible to check on that rig, to make sure it was operating in
top condition.

What's that?  Did I hear some comments from the back row?  The 7.290
traffic net has been in operation since Fone was allowed on 40m (1956, I
think).  None of the regular Net Control operators, nor the people who
checked in were on SlopBucket.  The mode may have changed, but the
Net is -still- in operation, Mon~Sat from 10am to Noon, Central time, and
from 1 to 2pm Mon~Fri, and is still operated as a public service.

73 = Best Regards,

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