Watts Up – Episode 2: the SPARCstation-10 chassis and power needs


For it’s time (1992) and capability, the SS10 used a very slimline chassis, with a very unique PSU shape:
SS10layout The PSU is the grey box running along the bottom of the picture (the matchbox is to give some idea of real size). Just above it, and screwed onto the PSU box, are the three cooling fans which pull air through the PSU and push it across the CPUs (L-shaped black heatsink, two modules stacked vertically) and add-in SBus cards beyond.

When you remove the SS10 PSU, there’s a little surprise – the bottom of the chassis is not flat!
APS39bay – which restricts the height available even more. The view of the PSU from the back side sheds some more light:APS39b. The top-half of the fans cools the PSU and the top CPU, the bottom-half cools the motherboard and the bottom CPU. What a wierd beast!

So there just isn’t room for a “traditional” almost-square PC-type power-supply. Hey, why not go for one of those modern funky long-and-thin “FlexATX” or “submicro-ATX” PSUs? Well, such modern PSUs simply cannot provide enough current on the 5V output rail – it’s been more than 15 years since PC CPUs or PC add-in cards used a 5V supply – everything had gone 3.3V by then (until Intel/AMD CPU supplies temporarily went 12V crazy for a few years). We are going to need 21A@5V, 3A@12V and 0.1A@-12V.

After a lot of research last year, it turns out that the 175W-output TDK Lambda NV1-350TT PSUs could provide sufficient 5V/12V/-12V current for the SS10, with a bit to spare – and they are small enough that there is at least a fighting chance to squeeze one in there:
NV1pic1 NV1_overheadThe particular NV1 I have is the “-N” model with soft-on/soft-off capability, which is a bit wider than the “plain” NV1 – the highlighted rectangle in the picture above shows the additional section.

Just for comparison, here is how the two PSUs look alongside each other: PSUcompare1PSUcompare2

Fortunately, the NV1 is a little smaller than a 3.5″ HDD in width and length, even aftre allowing for small fan to blow lengthwise, and is the same height as a half-height 3.5″ HDD – so the plan is to locate it in one of the drive bays instead. I will need to preserve at least some of the old PSU chassis – the end that has the SS10 AC inlet and DPDT mains switch.

Time to get started!

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