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
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
>
>
>
> --
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