Dan,
The EB-104 uses an MC1723 voltage regulator. D5 is a 28 volt zener for
the input of the regulator assuming you are obtaining the bias voltage
from the 50 volt supply. I assume you have removed D5 and R6 and are
supplying 13.8 volts to pins 11 and 12 of the regulator. You should be
able to adjust R5 for about 10 V at pin 3 of the regulator. With R1,
R2, R3, and R4 adjusted so that no voltage appears on the wipers, apply
50 volts to the board. Adjust R1 through R4 while monitoring the
current from the 50 volt supply. Adjust each pot for 250 ma additional
current i.e. 250, 500, 750, and 1000 ma. The MRF150s should not draw
any static current on their gates. If the voltage on pin 3 of the
regulator is dropping as you adjust the pots, check the input to the
regulator for stable voltage. If that is ok then you must be drawing
current in the gate circuit so look there or check that the regulator is
working properly.
Hope this helps,
Tom W0IVJ
On 1/16/2011 2:17 PM, Dan Sawyer wrote:
> All, I am building an eb-104. After several false starts, assembly
> errors, the board is up and running at low power with two devices. The
> current question is related to the bias circuit. I am using a 13.8 volt
> supply and have the bias set to 6 volts. When the first device is
> brought up to 200 ma the bias source drops to 5.8 volts. When the second
> device is brought up the voltage drops even further. Needless to say
> this would make balancing 4 devices difficult.
>
> Is there an update to the bias circuit?
>
> Does anyone have suggestions on how to debug the voltage regulator circuit?
>
> Thanks, Dan
>
>
> _______________________________________________
> Amps mailing list
> Amps@contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
>
>
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|