I am helping a guy with a dead IBM 3279 terminal The PSU does not seem to work. But as usual it is impossible to find any schematic online for IBM stuff. Just interconnection diagram and high level drawings. Anyone? Now the PSU circuit seems to be quite simple with just one IC in it. A chip marked 4216092. https://i.imgur.com/WMe7DgU.jpg At least it matches very well with other TI chips manufactured in the same time frame. The rest is looking like a quite simple flyback mode PSU: A transformer with air gaps, no output filter inductors and one single power transistor. Is there a cross reference list available for IBM numbers to standard chips? It shouldn't be that hard to figure from the how it connected, though, since it is most likely a standard chip. It can be a TL494 or SG3524 perhaps? /Mattis