Jacques
I find your comment about trying different tube types in a socket interesting.
No two tubes of any designation have all of the very same characteristics.
This is do to the tube's bogie number which is just a statical average, a bell
curve if you will. It is quite easy to match two tubes to a single bogie
number, more difficult to match two bogie numbers and very difficult to match
four. I have been told that swapping tubes of the same type found in the same
radio chassis could improve overall performance for final acceptance testing.
For a radio initially designed during WW2 and first advertised in 1946, I would
think that the tubes initially used in the 51J could be easily replaced with
tubes of improved characteristics which should make for a better radio. The
6BA6 and 6BE6 were released for production by RCA in October, 1945. Tubes with
higher gain and lower noise, like the 6BY6 and 6CS6 were both released in 1953.
They were designed for the demanding TV market. The four digit tubes
mentioned were made for the burgeoning computer industry and were released in
1965 and 1985 respectively. I find it interesting that new computer tubes were
developed in 1985! All of these have the same 7CH basing diagram.
Perhaps all of this is similar to the improvement made in the performance of
the WW2 Spitfire? All that was changed was to put 100 Octane gas into the fuel
tank! <grin>
Regards,
Jim
Logic: Method used to arrive at the wrong conclusion, with confidence. Murphy
On Wednesday, October 8, 2025 at 02:45:13 PM CDT, Jacques Fortin
<[email protected]> wrote:
Hi Jim,
Yes, this should have been the Bill Orr PD mod.
As we are there, VE3TOU (Treetops Circuits) made a plug-in PD for it (well,
kind of) see attached.
About trying different tube types on a R-388 PD, I never do it, despite I have
one Collins R-388 but it is still to be restored.
73, Jacques, VE2JFE in Montreal
Jacques
Good catch.
I have a 51J-3 aka R-388 that also had the 6BE6 Product Detector mod installed.
It must have been inspired by the Bill Orr Ham Radio magazine article. I
agree that it doesn't work very well. I removed the mod but haven't decided on
what to do. Either make it work better in SSB or return it to original
condition. I think that there are several pentagrid tubes that have the same
pinout as the 6BE6 but are less noisy with higher gain. Has anyone tried the
6BY6, 6CS6, 5915 or 7036 in place of the 6BE6?
Jim
Logic: Method used to arrive at the wrong conclusion, with confidence. Murphy
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