Lambda D-9172-2 400Hz Regulated Power Supply

Lambda D-9172-2 front view   Lambda D-9172-2 back view

The Lambda D-9172-2 provides 5 and 15V DC outputs, (I think) completely isolated from one another, with remote sensing for both the positive and negative leads. The 5V output is rated at 14A (at 40C) while the 15V output is rated at 4A.

Input is 115V at 400Hz. That makes it pretty useless to me. I have to however appreciate the build quality.

Inside from the front  Inside from the left  Inside from the right  Transistors  Regulator  Trimpot

This is serial number A51204. Seems they made quite a few of these. Very nice.

Butchered unit

This one (A51258) however, had a previous owner. He didn't keep much (somewhat understandable, not much one can do with a 400Hz transformer, but I would have kept the output capacitor), replacing the power transistors with LM338 voltage regulators which are good for 5A each.

This is frankly a hack. Some of it's OK, even those scramblewound chokes probably do the job (as opposed to the little blue ceramic capacitor out on a limb there) but I do draw the line at the masking tape wrapping around said chokes. And the crazy wiring. There's a rebuild on the cards -- 2N3055 transistors good for 15A each (not that I'd get 60A from the transformer), decent wiring, and maybe a venerable 723 -- or keep one of the 338s, boost it with 3 x 2N3055 using a circuit I once used to get plenty 5V for playing with single board computers. (TI Appnote AN-103).


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