[AMRadio] Re: The Tucker KW


Patrick Jankowiak recycler at swbell.net
Sat Aug 13 02:32:49 EDT 2005


Hi John,

IIRC, it has on the screen terminal of the socket, several disk ceramic 
caps in parallel, along with a rectangular mica cap about 1"x1.5" square. 
The leads are as short as possible. The filament also has one side 
connected directly to ground with a fat copper strap. I have to go look at 
it, maybe this weekend and give an answer more accurately. (right now it is 
behind a huge stack of DEC litterature a friend is picking up to scan SAT 
morning.)

I certainly can use those chokes, if they are the ones I recall, they are 
these big ones with ceramic terminals that had at one time some er.. 'oil' 
splattered on them? I only have 6H in the power supplies and would like to 
replace the ones I have subbed in because they are questionable for the 
voltages.

Please let me know about the Raytheon chokes, I'll report on the rig as 
soon as I can get to the backside of it and remove the panel.


Patrick

> From: "John Lyles" <jtml at losalamos.com>
> Subject: [AMRadio] The Tucker KW
> To: amradio at mailman.qth.net
> Message-ID: <209fa5bedabdc896999b5bbd0365829c at losalamos.com>
> Content-Type: text/plain; charset="us-ascii"
> 
> Patrick
> What sort of bypass caps does the screen connection have. How long are leads? I would try to put a good VHF bypass in there, if possible, something with very short leads to chassis from the tube pins. One cap that comes in mind if the American Technical Ceramics 100E style leaded chip capacitor. It has wide strips for leads, very low inductance. 390 pf value tends to have zero impedance at 200 MHz (self resonance) and higher values look like an excellent RF short at correspondingly lower frequencies. You can check the ATC website and see a chart of impedance versus frequency for these caps  I believe. 
> 
> In addition to the ATC cap, have some good lower frequency bypass like two x 5000 pF or so in short leads ceramic disk or doorknob style RF ceramic RF caps (5 kV). 
> 
> A series grid 'stopper' resistance isn't a bad idea, but you shouldn't need that high a value (much over 50 ohms) if it is working. I would be suspicious of the anode circuit having a parasitic resonance that is getting back to the grid and regenerating. I cannot remember from the photos if it had parasitic suppressor on the plate lead? 
> 
> I never shipped you those Raytheon RA1000 power chokes, do you still need one or two to replace the one with broken studs? 
> 
> 73 and good luck with the 4x1K
> John 
> K5PRO
> New Mexico 




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