[R-390] R-390A Current Regulator Tube replacement?

[David Wise]

Roy: Yes, the 25V winding is grounded.

While Dan's mod can be done very neatly without a prohibitive amount
of effort, I give a thumbs down because as Roy said, it makes the
IF deck incompatible with the standard power supply module.  Although
the 12BA6 mod renders the IF and PTO incompatible with standard PTO's
and IF's, they at least can be restored without removal/rewiring.
If you aren't keen on regulating the heaters, I favor the 42 ohm
resistor mod because it represents the absolute minimum effort to install
and remove.  Myself, I want to regulate them, and after a long hiatus
I've resumed work on the 3DW7D 2.0 .  Meanwhile, schematics of the
3DW7A are free for the asking, but only a zealot like me would make
the effort to squeeze it into a tubester format, and if you give up
the format, there are easier regulators to build.  None cooler
though -- in either sense!

73,
Dave Wise (SWL in Portland OR)

> -----Original Message-----
> From: roy.morgan at nist.gov [mailto:roy.morgan at nist.gov]
> 
> Quoting Dan Rae <danrae at verizon.net>:
> .. run the two oscillator tube filaments from the 
> > otherwise unused 12.6 Volt center tap on the power transformer. 
> 
> Is one end of the 26 volt winding grounded??? I am not sure 
> without getting out
> the schematic.
>  
> > Anybody tried this before, or got any comments for or against? 
> 
> One comment is that it means the modules are now not 
> interchangeable, at least
> to some extent.