Monday, December 13, 2010

Here we have another variable power supply, an EC Apparatus Variable DC Supply that is a touch worse for wear.

My guess is that this either took a spill from say, the back of a truck, or someone intentionally did this when they misapplied power to themselves. I'm still surprised that the glass on the meter didn't get punched out.

Since I've already got a couple variable DC bench supplies my plan of action was to gut this unit for parts and move on with my life, but something is different here.

This is wired in the classic half wave voltage doubler configuration. The caps are each 80mf at 500V, and the diode strings are built from three cascading 1N1449 diodes, which are spec'd at 400 PIV each.

So, what I have here professes to be a trashed high voltage DC supply, which is another matter altogether.

I question the wisdom of building a power supply in a 17 gauge aluminium enclosure, this former corner sides with me. I'm under the impression that the point of impact was at the 12 o'clock position of the variac dial, and that most of the damage stems from the base (on which over 7 pounds of iron reside) having its momentum arrested through the squish of the upper 17ga shroud. The corner pictured above is situated at the opposite end of the suspected impact, so the distortions would be of a pulling nature at this point.

Still, a variable DC supply that will power tube circuits is something I've needed for a while, so I'll undertake the repair process, begrudgingly within the original enclosure. I'll try to avoid dropping it from heights or using it to hold up my car though.

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