Power supply project: Input and filtering

Tracing out a schematic for this power supply has been pretty fun so far. It’s also been a good excuse to learn how to use KiCad.

So far I’ve made it past the rectifier and filtering capacitors up to the power transistors. I’m pretty impressed with the way the innards of this thing are put together. The bridge rectifier part took me a bit to figure out until I realized there were two different stud mount diodes in it.

Rectifier diodes
Rectifier diodes
Rectifier diodes
Rectifier diodes

I’ve come across a couple types of components that took me some searching to figure out what they were (still not quite sure what one of them is). This one in particular is one I haven’t been able to identify.

Mystery component. Diode? Transistor?
Mystery component. Diode? Transistor?

It’s connected to one of the outputs of the bridge rectifier and the control board at the top. At the bottom it’s connected to an air core inductor and parts that lead to the 2N5886 power transistors. A Google search of the numbers printed on it take me to a single page at a store that has it listed as a rectifier diode.

This is the schematic I’ve cobbled together so far. Things start to get a bit confusing after the rectifier, but I think it’s reasonably accurate.

Power supply schematic
Power supply schematic

I wasn’t able to find symbols for everything in the KiCad library, particularly for the connectors, so I just used something that looked reasonable.

This has been a fun exercise so far. The power transistor section will probably take me a while to figure out.

Power supply project

The dead power supply I picked up at the TARC swap meet last year has been sitting in a couple of closets for the past year, and now I’m finally getting around to poking around inside.

Power supply front panel
Power supply front panel

The innards of the power supply look pretty good. Everything looks pretty clean, no scorch marks, and hardly any dust.

Power supply innards
Power supply innards

Looking at the back panel doesn’t inspire much confidence though. Looks like at some point someone soldered a regular power cable to the original (I think) AC input and covered it with heat shrink. I might have to do something about that when I start working on the power supply.

Back panel AC in
Back panel AC in

So far everything looks in pretty good shape. Not sure what the problem with it is (aside from a blown fuse), but before I dive in and start mucking around, I’m going to see if I can reverse engineer a schematic for the power supply. There aren’t any labels on the power supply so I can’t look anything up. Should be a fun exercise.