[R-390] Tube substitutions

[chuck.rippel at cox.net]

I've done the 6BZ6 mod in an R390A documenting the useable sensitivity 
before and after.  The 6BZ6 had more gain but it only served to amplify 
the noise along with the signal.  When measuring the net 10db S/N + N 
performance between the 2 tubes, there was no improvement in 
specifications.  Only the meter deflected higher.  Seems that 
demonstration is in the 2nd R390A video but I could be wrong.

It would be interesting to see if the 6BY6 mod for the SP-600 actually 
improved the real sensitivity (10db S/N + N).

Chuck Rippel


On Tue, Apr 10, 2012 at 12:02 PM, r-390-request at mailman.qth.net wrote:


> List,
>
> Has anyone substituted the 6BY6 pentagrid mixer for the 6BE6 in either 
> one or both of the SP 600? ?If so, what were your results?
>
> The 6BY6 had about three times the trans-conductance of the 6BE6 
> according to my RCA tube manual which implies that it would have 
> better performance just as it has proven to be the case by replacing 
> the 6BA6 RF amplifier tubes with the 6BZ6 types.
>
> Also Hallicrafters used it in their receivers and Blakeslee used it in 
> his SP 600 conversion article.
>
> Regards,
>
> Perrier
>