21-09-2019, 01:11 PM
The PS25A is a combined PFC and main switcher IC. In other words, it can do the whole lot. So I'm confused by the presence of the TL594. It's possible they decided to only use half of the PS25A - the PFC half - but if so, why not just use a chip that does PFC only? There's no shortage of them.
The standby supply has its own controller on the main PCB (the DIL 7 package), so it's not related to that.
If this was a supply that made other rails using separate DC-DC converters for each (as I described on that other thread), then the TL595 would have something to do - though there are better choices for secondary-side buck converters. Noting that the large toroidal inductor on the main PCB has at least 2 windings, it's possible it's being used as a mag-amp to further improve the regulation, but that would be unusual for a single rail supply.
I really need to get my hands on one of these to find out what's going on - I find it hard to process it all from photos - even good ones like these. I have a DC7800 SFF here, but that uses a different PSU. I'll take it apart later, as the innards could be the same or very similar, but IIRC that one is a conventional multi-output one. Failing that, I'll borrow one from the old machines at work that I mentioned earlier...
The standby supply has its own controller on the main PCB (the DIL 7 package), so it's not related to that.
If this was a supply that made other rails using separate DC-DC converters for each (as I described on that other thread), then the TL595 would have something to do - though there are better choices for secondary-side buck converters. Noting that the large toroidal inductor on the main PCB has at least 2 windings, it's possible it's being used as a mag-amp to further improve the regulation, but that would be unusual for a single rail supply.
I really need to get my hands on one of these to find out what's going on - I find it hard to process it all from photos - even good ones like these. I have a DC7800 SFF here, but that uses a different PSU. I'll take it apart later, as the innards could be the same or very similar, but IIRC that one is a conventional multi-output one. Failing that, I'll borrow one from the old machines at work that I mentioned earlier...
