In article . edu, wcm1
@NOSPAM.cornell.edu says...
I've been renovating a Malden Mass Monster...NC183D. It sortta
works, but the B- is supposed to be -21 volts and 500 ohms from chassis
ground acting as the bias for the audio power amps and the negative end
of the RF gain pot.
On my rig the line measures only millivolts negative and 0.4 ohms
to ground. I thought first I had a shorted electrolytic and replaced
all the caps on the line. No joy. Then I thought the transformer
center tap might be shorted to the case, so I unsoldered it and measured
it. The Xformer is very healthy but the line still measures 0.4 ohms to
ground.
Any suggestions what I should look at next?


Thanks to all those who responded. I found it. After pulling the
main p.s. electrolytic and effecting no constructive change I
undsoldered and checked the *one* electrolytic on the line I hadn't
previously replaced...C19. It looked so new I'd figured the previous
owner had replaced it...but it was shorted. I replaced it and now have
normal bias and RF gain control operation...and signal thru-put on all
bands. There is still a lot of work to do to restore full original
performance, but it's "over the hump"

tnx de kc2lvq