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ortek_service · 18th Mar 2021, 5:12 am

It's probably not surprising that an electrolytic capacitor was causing the main fault, as they often do in these if it isn't high-value start-up resistors going even higher resistance due to high voltage on them (why they normally put a few in series, to try to prevent that)

I had thought that T3 / T4 might have been output filter inductors.
But from looking at the underside, it does seem these are across the isolation barrier gap and drive the 2N6672 transistors.

So it would appear that F1 & F2 are both mains-side fuses, and that there may actually be 2 switch-modes on the board, with a slave one producing a supply for the circuitry to control the master one.

And if you've got 16V coming out of the 7812, then it does look like this has gone a bit shorted - unless there's an issue with its ground pin reference connection.

Well done on the inverter DIY-alternative to a mains isolation transformer !
Luckily, most SMPSU's won't have an issue with the quasi-sine output from these.

18th Mar 2021, 5:12 am	#58
ortek_service Octode Join Date: May 2018 Location: Northampton, Northamptonshire, UK. Posts: 1,444	Re: The Transam Triton Personal Computer It's probably not surprising that an electrolytic capacitor was causing the main fault, as they often do in these if it isn't high-value start-up resistors going even higher resistance due to high voltage on them (why they normally put a few in series, to try to prevent that) I had thought that T3 / T4 might have been output filter inductors. But from looking at the underside, it does seem these are across the isolation barrier gap and drive the 2N6672 transistors. So it would appear that F1 & F2 are both mains-side fuses, and that there may actually be 2 switch-modes on the board, with a slave one producing a supply for the circuitry to control the master one. And if you've got 16V coming out of the 7812, then it does look like this has gone a bit shorted - unless there's an issue with its ground pin reference connection. Well done on the inverter DIY-alternative to a mains isolation transformer ! Luckily, most SMPSU's won't have an issue with the quasi-sine output from these.