[hpsdr] Munin lll

[rwfish]

Hello,
I recently finished building a Munin lll amplifier. I am having trouble setting up the bias for T1 and T2. I assume that the devices should be biased at 1A each as they are in the Munin 2. I can’t seem to get the the current to 1A on either device with the associated pot. I am measuring the total current to the board with a DMM in series with the +13.8 line. I thought perhaps the 10K thermistor circuit was loading down the bias circuit so I lifted one leg of the thermistor. This did raise the current somewhat however still not enough. I also have a bit of an imbalance between the devices (ie different gate voltage to get same source/drain current). The current maxes out at 800ma on one device and 400ma on the other. I then lifted the gate connection on each device and measured the range of the bias voltage. Both bias channels are identical at 2.5 to 4.3vdc. I then used an external dc power supply to bias the Mosfets. I was able to swing both mosfets all the way up to 5 or 6 amps or higher independantly with an external bias supply, but I do have to go slightly higher in voltage than 4.3v. Maybe 5v or so. I am stumped, any ideas?

Sorry for the long winded post but I wanted to include most of the details.

Thanks & 73,

Bob. K6GGO