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Saturday, February 24, 2018

2018 Novice Rig Roundup Update

It looks like I'll have three stations available for the 2018 Novice Rog Roundup: Drake 2B / EFJ Adventurer, NC-57 / 6AG7 Sucker Stick Xmtr and NC-303 / Eico 720.

Eico 720s seem to have power transformer problems. I have two, each with a bad power transformer. Lacking a drop in replacement I went to the 'net looking for a replacement.
What I found was a 120V to 480V @ 150VA industrial control transformer. Obviously it didn't have a filament winding but I decided I could live with a separate filament transformer. I changed the '720 rectifier to a silicon bridge rectifier, added a 10 mfd cap to the input of the power supply filter and installed
a "back porch" for the filament transformer. Now under load 530 VDC is delivered to the 6146 instead of the specified 560 VDC...close enough to go on the air at 75 watts input. It tests out just fine. Now I have a couple of minor cosmetic changes before I pair it with my NC-303.

I'm almost ready and really looking forward to this year's NRR.