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

[Dennis Monticelli]

Dan,

It is probably one of the running changes Drake made to the R4B throughout
its build cycle.  I have a very early R4B and it has the VR tube, which was
very noisy and unstable when I originally got the radio.  Turned out to be
a bad OB2.

Good luck tracing down your audio quality problem.

Dennis AE6C


On Wed, Oct 30, 2013 at 7:33 AM, Dan W. Dooley <dan at dooleystreasurechest.com
> wrote:

> 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
>
>
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