[R-390] R390 B+ Expected Tolerance

[Barry]

Jacques, Jim,

Thanks for the replies.

I didn't check C606 or C608 so I have something I need to do now!  Hopefully that'll get the regulator back up to 180v.

Thanks again,
Barry - N4BUQ

----- Original Message -----
> From: "n4buq" <n4buq at knology.net>
> To: "R-390 Mailing List" <r-390 at mailman.qth.net>
> Sent: Saturday, November 12, 2022 8:58:33 PM
> Subject: R390 B+ Expected Tolerance

> 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