[Boatanchors] DX 100

[Garey Barrell]

Just a guess, but sounds more like grid emission in one or both of the 
6146s.  The grids of power tubes tend to accumulate cathode material as 
the tube ages.  With positive grid current, as the tube (and the grid) 
heat up, the grid begins to emit some electrons itself.  This causes the 
grid go more positive and to heat more, which causes more "grid" 
emission, which drives the grid further positive until it loses control 
over the primary electron flow and the tube conducts as much as it can 
until it or the power supply gives up.

It's late and this may not even make sense, or I may be replying to 
another message, but try another pair of 6146s in the PA.

73, Garey - K4OAH
Glen Allen, VA

Drake 2-B, 4-B & C-Line Service Supplement CDs
<www.k4oah.com>



Joe Dube wrote:
> I need a bit more help with the DX 100. Can anyone out there give me an idea of what might be the problem with my DX100 slowly falling Grid current.  This happens after I peak the grid current to about 5 mils  and then key the transmitter. It will hold for a few moments and then begin to fall to zero. At this point the plate current goes all the up to the end stop and I have to shut the plate switch off quickly.  This happens with a crystal as well as the VFO.  I changed the 20 mfd caps in the 6al5 circuit which supplies grid voltage.  I am at the end of my rope with thing.  I think I have tried almost everything. Any ideas will be appriciated.
>
> Joe K4TR
>
>