Well I finally get back to the AS4100 and removed the PSUs. I took the opportunity to inspect the second PSU that didn’t go pop while I was in the mood. The PSUs are very easy to open, 2 Torx-10 security head screws and the 2 halves slid apart with next to no effort. 2 large cables connect the pair of circuit boards. The 6-pin plug at the back edge is easy to remove, the 4-pin in the middle is a swine as one of the press-in latches is part obscured by a transformer body.
PSU 1 (that went pop) is very clean and looks in good order inside. There is no staining or signs of damage to the boards and no blown components. As I suspected when the PSU didn’t shut down in spite of the nasty smell, the cap that blew was a main filter capacitor. In fact, it was inside the filtered mains input socket, so the mess was very much contained. Even better news is that we had a replacement filtered mains input socket on stock that fitted right in it’s place. A little soldering (thanks, Dad!) and the new filter is in place and the PSU back together.
PSU 2 is also very clean and looks in good order inside. There wasn’t much to see, again nothing looked out of place and there was no dirt or contamination. I did discover one interesting thing – the Mains input filtered socket had already been replaced! So I guess that happened to the previous owner too. Makes me fell a whole lot better!
As Mark Wickens advised in a comment on my previous post, it’s not uncommon for mains filters to blow. Dad concurred on seeing the filter socket and the evidence of the blown filter cap.
Next step is to re-install the PSUs in the system drawer and power them up and see if both get OKAY LEDs on the power management board.
If they are both okay in spite of my poking around in them I then need to turn my attention to diagnosing the remaining blank LCD and not starting up issue. That’ll all have to wait for the weekend I think.