[Drake] Do I need V11 in the R-4B

[Dan W. Dooley]

I am looking into a audio distortion issue with my R-4B.  It's not
drastically noticeable but enough for me to recognize that the sound quality
is not what it used to be in terms of the cleanness of the sound.  Most
noticeable on CW where the signal is strong enough to be pretty well noise
free, there is a slight noise sound which sometimes we've heard described as
sounding like it's under water.  I know there are many possible causes and
I'm working my way through them right now.  
 
At the moment my focus is on the purity of the power supply voltages and the
problem of ripple.  I have replaced the main multi-section electrolytic
(which had gone bad a few years ago) with individual and smaller
electrolytics and until recently everything sounded ok.  There is very
little ripple in the form of a saw tooth shaped wave riding on the power
supply voltages, particularly the +160 branch which does go to the audio
output tube.  What is more curious is that though the actual ripple is
rather low (about 0.3 VPP) it is rather erratic and with the scope set on AC
input and of course the sync is correct, the waveform is somewhat erratic
and it is microphonic.  That sounds like a connection issue somewhere even
perhaps in one of the tubes.  I'll work my way through that issue.
 
Though I may have noticed it before, I probably have forgotten but though
the schematic shows a VR tube OB2 there is none in the radio.  Where the
socket for that tube would be in the chassis is a hole where the socket
could be but it is covered with a plate.  It's factory as the plate is
copper just like the chassis.  My question is, does anyone know if this was
a version change and if it was something added or something removed in later
models?  Would there be any benefit to actually adding one?  I can do that
if it looks like it would be a good idea.
 
 
Dan W. Dooley
  email:  <mailto:dan at dooleystreasurechest.com> dan at dooleystreasurechest.com
   <http://www.dooleystreasurechest.com/> Dooley's Treasure Chest