I understand the meter protection scheme but if you take the time to read the
AL-82 schematic provided with the amplifier you will see on page 13 the
capacitor board is listed as 50-01167-1 and on page 13 the same board is listed
as 50-01143-1. On the latter there is tie point named PCM. Maybe (P)late
(C)urrent (M)eter but it's unclear what point it is attached to the metering
board. Point to point check of wiring on the amp has it connected to the B- side
of R1 and R2.
Back to drawing.....
Don, W6OA
R. Measures wrote:
** The easy solution is to protect the meter movements with back to back
3a diodes across the movements themselves. Protecting the shunts
requires some knowledge of polarity at the shunt, understanding that Si
diodes Begin to conduct c. 0.5V, as well as knowing basic Ohm's-Law.
Comparing grid and plate current metering circuits of the SB-220 and AL-82 I
find the AL-82 grounds the negative side of the plate meter. Trying to
sort out
how to install the metering glitch diodes is a bit confusing here. Of course
Ameritron's idea of an amplifier schematic doesn't make things any easier to
trouble shoot.
Can anyone give me some help as to where to physically (electrically that
is)
put these diodes. I can understand the one across the grid current shunt
resistor but I need help with the three in series from -HV to ground.
Is there by chance a schematic of the AL-82 that incorporates all the sub
boards
in one print?
Thanks in advance.
73, Don, W6OA
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