Tuesday, 15 May 2012


Making some progress still, I started off by emailing Hypertherm, I heard they had really good customer service so I thought I would ask for some tips from tech support. Initially they did not seem to understand my request, "the power board might be faulty". So I explain that I know it is faulty but wonder if they might have an idea of the likely culprit that could cause this fault. I got this back: "We are not aware of any problem with the power board. You will need to replace it." OK so there is nothing wrong with the board I just need to replace it. To be honest I am not suprised they are not massively helpful, most companies are not interested in assisting repair.

So I move on and look at the schematics which are laid out to match the board which is nice but resemble spaghetti. With some help from a friend I redrew the first stages of the circuit so I could actually understand it and determined that the cause of the high current that was cooking the resistor was probably either the rectifier that produces rectified DC to the power factor correction inverter or a capacitor on the rectifiers output. Some resistance testing suggested the former. So I took the board off and this is what I found:

These are two bridge rectifiers that are wired in parallel, each can handle 30A so they should be more than OK for the 30A max input currents. But notice the small hole at the bottom right, yep it's fried!!!!

And wow, it blew a small hole out of the aluminium heat sink, impressive!!! I've now taken the rectifier off the board and have discovered the first real problem. It is no longer made and worse, the pin out is non standard!! It sits a fair way off the board so I have to hope I can find a way to make some sort of adapter for a new rectifier, we shall see. And lastly, a few photos of the insides for context:

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