27 Feb
2023
27 Feb
'23
5:32 a.m.
On Mon, Feb 27, 2023 at 10:29 AM jake utley via cctalk
<cctalk(a)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