Recycled Transformer Mk1
Dec 19, 2017
2 minutes read

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I modified and re-housed a transformer the other day. In unrelated news, my LM4752T-based amplifier exploded. The transformer has independent ~12V and ~5V low-current rails, and two ~28V rails coming off a center-tapped secondary winding. Originally it could be switched between 110V and 240V for the primary, but I took that out and hard-wired it to 240V since that’s the only voltage you’ll get out of the wall here in Australia. Not sure yet how much power it can actually deliver, but I expect it’ll be at least a hundred watts. That should be plenty to power some hobby projects.

I’ve got the 5V and 12V rails going through bridge rectifiers that are pressed up against the case for heatsinking. These will be used to power auxilliary functions like cooling or monitoring. The 28V rail is configured as a full-wave rectifier with two diodes.

Right now there’s no smoothing or anything on the outputs - I’m thinking of putting some basic capacitor/coil filtering on the 5V and 12V rails, and a linear regulator on the 28V rail to keep the voltage constant and stable. Haven’t decided yet though.

I plan to insulate the terminals on the transformer better. Right now it’s a death trap if you manage to shove your hand in there. I’m also going to get a fused socket, or put one inline with the input so it won’t kill you if you spill a drink on it.

If you’re more familiar with transformer wiring than me, please do let me know if I’ve done anything particularly wrong.

Anyway, picture time!

Top view of my recycled transformer, showing wiring and the power switch

Side view of high-voltage wiring on my recycled transformer, showing terminals straight on

Side view of my recycled transformer, showing rectifiers

Side view of high-voltage wiring on my recycled transformer, showing terminals from an angle

Side view of low-voltage wiring on my recycled transformer, showing terminals from an angle

Side view of my recycled transformer, showing power switch and rectifier construction

Front view of my recycled transformer with the case on, showing power input and fans

Back view of my recycled transformer with the case on, showing output wires and top fan


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