Wednesday, 16 May 2012

The plan

The original rectifiers sit off the board by quite a way and are then screwed to the heat-sink. This means there is a gap between the board and the rectifier. I'm hoping that I can bend the leads of another rectifier to fit. The original devices were Semikron SKB 51L16-W, which can do 29A forward current and are rated to 1600V.

The selection of leaded rectifiers available is not huge but I found a Vishay GBPC3512W which can handle 35A and 1200V. I lose a little on the voltage overhead but I suspect 1600V was overkill anyway. The package has a similar thickness but a different pin out. The following is what I plan:

It does not show that well but the general idea should be obvious, the twisted positions are the new rectifiers, twisting reduces the length of lead between the board and rectifier, much more and they probably would not be long enough, it still might be boarder line because of the stand off. I think I will turn some spacers to act as a jig when soldering and to ensure the right stand off. Will probably have to be split so I can remove them afterwards.

If this doesn't work then I may have to try and make some weird intermediate PCB from copper sheet, sounds like a recipe for disaster. While I wait for the rectifiers I'll check the rest of the board, I may even try "booting" from the remaining rectifier, if all else is well it should work and if it blows it shows the problem lies further in.

And in case it helps anyone this is the first draft of the first stages of the power supply where the problems have arisen (drawn in Diptrace).

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