>
>
>
> The easy test doesn't tell much. It Might be a
> better idea to check the grid current metering
> shunt and multiplier, (R-20 & R-22) from the
> negative meter terminal to ground while
> the meter
> switch is in the grid current position as Q4 and
> Q5 isolate the metering circuit from B-
> while off.
> 680 + 3.3 ohms.
> Paul
>
That measurement should be from from the positive
meter terminal to ground with the negative
terminal disconnected, blurry eyes last nite!!
> Paul Hewitt
> WD7S PRODUCTIONS
> QRO HOMEBREW COMPONENTS
> http://wd7s.home.att.net
>
>
> > -----Original Message-----
> > From: owner-amps@contesting.com
> > [mailto:owner-amps@contesting.com]On
> > Behalf Of Jim Barber
> > Sent: Saturday, June 02, 2001 6:21 PM
> > To: W8JI@contesting.com; amps@contesting.com
> > Subject: Re: [AMPS] continued Alpha work
> >
> >
> >
> > Skipp,
> >
> > Tom's analysis brought up an excellent
> > point. If the amp
> > is an original PA-77, there should be 5
> > megohms resistance
> > between B- and ground. Easy test.
> >
> > Selected bits:
> >
> > >If the metering system is messed up
> > and he is trusting it to tune
> > >the PA, that explains why the output
> > is low. More than likely the
> > >grid meter is partially reading plate
> > current through a fault in the
> > >from the B- return to the chassis.
> > When that condition exists, the
> > >user will "overcouple" the PA because
> > he "thinks" the grid current
> > >is higher than it really is.
> >
> > Regards,
> > Jim, N7CXI
> >
> >
> >
> > --
> > FAQ on WWW:
> http://www.contesting.com/FAQ/amps
> Submissions: amps@contesting.com
> Administrative requests:
> amps-REQUEST@contesting.com
> Problems:
> owner-amps@contesting.com
>
>
> --
> FAQ on WWW:
> http://www.contesting.com/FAQ/amps
> Submissions: amps@contesting.com
> Administrative requests:
> amps-REQUEST@contesting.com
> Problems:
> owner-amps@contesting.com
>
>
--
FAQ on WWW: http://www.contesting.com/FAQ/amps
Submissions: amps@contesting.com
Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
|