[Boatanchors] A funny thing happened...

[SBJohnston at aol.com]

A funny thing happened while I was working on my BC-468A command transmitter 
project last night.  After restoring this pretty trashed rig and really 
spiffing it up (cleaning everying, silver-polishing the output tank, new caps, added 
bypassing on power connector, converting to 12v filament, etc), I paired-up 
the rig with my Heath UT-1 utility supply and was getting about 60-80 watts 
output.  The note was a bit harsh, perhaps T5, so I turned my attention to 
replacing the old filter caps in the power supply and while I was at it added a 
choke instead of the series resistance in the filter stage of the low B+ (making 
it pretty much just like an HP-23).

This virtually eliminated the ripple on the DC outputs of the supply, but the 
command set sounded the same.  Hmmm...  Then I figured I'd try running the 
filaments on DC from a bench supply instead of AC from the UT-1... and the CW 
note cleaned right up.  Sounded great.  To confirm my results I switched back to 
using the AC filament supply... and it still sounded great!  What the heck?  
Any ideas on what happened?  A couple minutes of running the transmitter 
filaments on DC and now it is OK on AC too??

The only other thing that happened in this change was that while changing the 
connections I accidentally fed the bench supply back into the filament 
winding of the UT-1, so it was exposed to current-limited DC at about 4-5 amps for a 
moment.  No damage was apparent ...but I'm really grasping at straws as to 
what happened...

Steve WD8DAS

sbjohnston at aol.com
http://www.qsl.net/wd8das
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