On Mon, Feb 27, 2023 at 10:29 AM jake utley via cctalk <cctalk@classiccmp.org> wrote: > > I’ve been restoring a RM380 I picked up not long ago and it’s been good news > and bad news. All the cards are in wonderful condition and the case is > presentable however the two BASF 6106 floppy drives are highly corroded and > probably won’t work again but this isn’t what I’m wondering, the original > supply is a little rough but looks tone perfectly restorable with the > exception of the key lock been stuck (problem to solve later) and I can get > all the parts needed to replace the three filters but it is a 70s linear > supply and if my s-100 experience has told me anything they might not be the > most reliable. What would you all recommend restoring it and keeping it > original or fitting some modern SMPS in its place. It is a low serial number > as well (691) but saying I want it to be reliable I’m torn.
I would certanly recomend keeping it original. My experience is that a linear supply, although less efficient than a switch mode one, is a lot more reliable. There's a joke about the crazy PSU in the Zenith ZVM1220 MDA monitor thst said unit combines 'The reliability of a switcher with the efficiency of a linear'. It's also a lot easier to fix a linear supply than a switcher and there are not high voltages on any of the semiconductors. Getting back to the 380Z, there's a schematic of one version in the service manuall. But even if it doesn't agree, you can trace out a schematic in under an hour and that's going slowly. It is a very simple unit using normal 3-terminal regulators in the standard way. I'd 'megger' the transformer just to be safe as the machine seems to have been stored in poor conditions. Then power it up with a 'lamp limiter' on the mains input and no load on the output (unplug the cables from the driives and the 1 or 2 10-way ribbon cables from the PCBs). Most likely it will be fine, even with the original smoothing capacitors. -tony
