- Blog entry posted in 'Teardowns', June 14, 2013.
Got this PSU from some cind of tele-com ''tower'' full of logics cards and smaller PSU's, i of course took all of them. This PSU powers up smaller ones, 3 in total, which in turn power up logics. This one weights little, not wonder, it has 300VA (2x30v, made in Finland :D) toroidal transformer inside, and almost all of the structure is stiff metal. And, one wall is completely profiled as one big heatsink. Also, case has numerous holes for cooling, so i'm not sure how much this brick'll heat when on maximum load!. input socket is basic 3 pin 230v, same which is used on computer PSU's, with exception this one has EMI filter. There are no mains switch, but relay, goodie. Fuse is 6.3A slow. Why so big fuse as this transformer is only rated for 300V? and case says 250w?. strange mystery box this one....and output connectors doesn't make life a bit easier, no markings whatsoever, and style is strange too! I could use information regarding this connetors ''life'', it looks like loose IDE, it does accept somehow normal pitch, phew.
Other winding on toroid goes to rectrfier, ''russian'' style diodes, big caps, 63VDC/10,000ufd (10MFD), there are two of these cans, i'd suspect these can give painful shock, gotta be careful with this thing :S. Aand next to caps, is come cind of choke, at least only one wire goes in and out, so is this some sort of LC filter?. From the choke, it ends to logics board. Other 30v winding from toroid goes straight to logics board. Now then, the logics board, hmm...
Board has, well, i would have guessed this ''old'' PSU wouldn't have any switching-mode in it, but there is, tl494, same IC found from computer PSU's!
couple beefy, To-3 case components are 2n3670 SCR's, which take care of high-power stuff. other metal cans are too in board, 2n3440 NPN transistor and 2n5415 PNP transistors.
so it seems this is SMPU, no wonder for this size-power ratio!
now, time for reverse-engineering, figuring out the puzzle of voltages....
power switch wouldn't hurt either :).
UPDATE 19.6.2013: made some measurements, sadly, noo useful voltages to be used outside of system....only one usable was SCR's output waveform, but even that is, well, bizarre, but normal waveform from SCR.
And, it seems that big fuse, 6.3A was purely for capacitors huge inrush current when they are empty, lamp-test indicated huge amount of current flowind when switching PSU on.
Too bad i dont have analog ampmeter or any other means to record or see the amount of this current.
