[Amps] Alpha 77D anode choke swap?

[Jim Thomson]

Date: Tue, 10 Apr 2018 16:03:16 +0700
From: Martin Sole <hs0zed at gmail.com>
To: amps at contesting.com
Subject: [Amps] Alpha 77D anode choke swap?

<Hi,

<About to swap the anode choke in my Alpha 77D for the Ameritron RFC in 
<the hope it will work on 12m without issue. Any gotchas or is it pretty 
<much plug n play?

<Thanks
<Martin, HS0ZED

##  will the new choke fit in there ?   The series  resonance points  could still shift up /down 
a bit,  depending on how close the new choke is to  surrounding stuff.   What did alpha use for
a bypass cap at the base of the oem plate choke ?   For  160m  use, they really should have a
pair of   4700 pf  disc ceramic caps.   I use the....ceramite  brand in the  mouser catalog...  also 
available at  henry radio in LA.  They come in  10 kv and also 15 kv rated, and I believe a  couple
of voltages lower, like  5 kv and  7.5 kv. 

##  Try it and see if it works on all bands.  You might want to go easy and pulse tune it, when
testing.  The Ameritron /  RF parts choke  is supposed to resonate at  12.6 mhz and 27 mhz. 

##  There should be zero issues  on 12m band.    Folks have had issues at the bottom end of 10m, when
using  a hb version of the  ameritron choke.   If it will fit in there, it should work.  Apparently Alpha uses
the exact same choke on their newer amps, identical.  Per  W8JI, the 2 bands that dissipate the most heat
when using that choke are  160m...and  10m.  

Jim  VE7RF