I just noticed that I had not copied the reflector on my response to
Carl's question of how I monitored the Grid current on the FL-2100B
so I am posting it now. Any comments about how I am proceeding will
be appreciated.
I arrived at the metering setup by closely examining what Heath did
with the SB200, determining that the FL-2100B and it are virtual
carbon copies of each other and then copied the metering circuit. In
testing this out I used an external 1 milliamp full scale meter with
an internal resistance of 86 ohms. I wanted a 200 milliamp full
scale reading so built a shunt from a couple of .22 ohm resistors in
series and put this across the meter. I made a paper 1 to 200 mill
meter face using the "VISIO" drawing program. The meter was then put
in series with the line running from the set point of the bias
resistor and the RFC that is wound on the 3.3K ohm resistor. I
brought the leads out through an air vent slot in the bottom of the
case and attached the meter and shunt.
Now that I know this works, I will do some rewiring of the Plate
Voltage meter so that it can do double duty and indicate Grid Current
as well. I am reluctant to add a switch to the panel so have the
following plan. The main power switch is DPDT with the switched AC
line being connected across both poles. This switch really could
have been a single pole so I plan to swap it out with the SPDT
"Forward Reflected" switch and then use the DPDT switch for the Plate
voltage Meter. The meter will be wired across the centre position
of both poles and I will use one position for HV and the other for
GI. This will result in sacrifice of either the Forward or Reflected
reading and I will choose to abandon the Forward reading. Since I
use a 1500 watt tuner, with good power metering, I will not miss this
indicator and will still have the reflected power metering active at
the amp. The only risk I see is that the SPST switch may not be up
to the current load. I will have to monitor this for heating and if
it does not work out, then I guess it will be time to get out the
drill and make a new hole on the front panel.
VE6TI
gordon Hungerford
ve6ti@telus.net
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