[AMRadio] A bit of Viking Valiant help

John Lawson jpl15 at panix.com
Sat Aug 27 13:56:54 EDT 2005

  I'm in the middle of a long, slow project to get my Valiant back in 
service. I've changed out the bigger power tubes, solid-state replacements 
for the 866s, and partially re-capped the rig, specifically the RF power 

   After finding (expensively) out that 'W' 6146s just don't work, I 
replaced the finals with new 'B's and power is now being transferred to 
the antenna / dummy load.

   Main bug:

   On the bands below 20M, however, and getting 'worse' as the frequency 
gets lower, the rig "runs away" after 15 - 30 seconds - the plate current 
rises fatser and faster and then needs to be shut down, lest another set 
of 6146s gets wasted.  ;}

   I have neutralized the transmitter per the manual, seems ok. Bias also 
set per sepc. LV rectifier tubes have been chacked (on a Weston 686) and 
seem within spec, though their performance under load is measurable only 
in situ.

   I left the doorknob cap alone because it's fine electrically and not 
cracked or discolored.

   Do the sypmtoms sound familiar to anyone? Before I spend a bunch more 
hours wearing out the transmit switch, I thought I'd ask those who have a 
lot more experience than I do with the Valiant.

   I can add more info/observations as needed, specific caps replaced, etc.

Thanks all!


John  KB6SCO

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