[R-390] R390 B+ Expected Tolerance

[Jacques Fortin]

Hi Barrry,

Have you checked / changed C606 ?
Any leakage from it will lower the regulated output voltage,
The output cannot be dependent on the 6082 tubes, unless they are worn out.
5651 tubes: when they are worn, the voltage across increases, and the
regulated output as well...
Have you checked all the values of all the resistors in the regulator
circuit ?
My own R-390 runs at 182V output, so I guess it is OK.
175V should not make a big difference, anyways...
If ever you need NOS 5651, let me know: I have few dozens of those...

73, Jacques, VE2JFE in Montreal

I discovered that the regulated B+ is running about 175v instead of 180v in
my R390.  I found R625 had drifted from 1k to 1.2k and, since I think that
was originally a 1%, I replaced it.  I now get very close to 3.7k at the
cathode of V609; however, that didn't change the regulated voltage.
I have five 5651s and except for one of them, virtually any two will produce
175v.  If that fifth tube is in place, I get about 185v.  According to my
Hickok 752A, the fifth one appears to have a different current draw at its
regulating voltage and that might account for the difference.
I have a spare 6082 that I've tried swapping in either socket with no
differences there either.
Running at 115VAC input and getting close to 300v unregulated input to the
regulator.
It leaves me curious as to how close to 180v is within specification.  I've
searched the manuals and I can't seem to find a tolerance for that.  Anyone
know?

Thanks,
Barry - N4BUQ