Who's rewired their house for this hobby?

[Eric Smith]

On Tue, Nov 25, 2014 at 7:42 PM, Jon Elson <elson at pico-systems.com> wrote:
> On 11/25/2014 02:18 PM, Eric Smith wrote:
>> Actually to 13 massive linear regulators on multiple large heat sinks.
> There may have been several versions.  The KL10B in a Decsystem 2020 we had

A DECSYSTEM-2020 uses a KS10, which has no ECL, and uses a big
switching power supply made by third parties. The KL10B was used in
the DECsystem-1090, but not in any DECSYSTEM-20 models.  The KL10BC
was used in the DECsystem-1090T, which was ran TOPS-20 but was not
marked as a DECSYSTEM-20.  The other DECSYSTEM-20 models (2040, 2050,
2060, 2065) all use the KL10-C, KL10-E, or KL10-E/R processors.

> had one big regulator that was a ring of "christmas tree" segments with a fan
> about 10" in diameter.

They wouldn't have used one big regulator because the remote sensing
wouldn't have been able to get a sufficiently uniform voltage on all
backplane segments, and that definitely *will* cause problems for ECL.
Also it has to be at least two regulators because the backplanes need
regulated -5.2V and -2.0V. And one big regulator for 315A of -5.2V
wouldn't have significantly less expensive then nine 35A regulators,
because it would have needed just as many pass transistors and just as
much heat sinking.

According to the maintenance docs, even the earliest production KL10s
used The H761 Regulator Assembly which had five heat sink
subassemblies for the pass transistors for nine -5.2V 35A regulators,
with room for a tenth, and four -2.0V 35A regulators.  Each heat sink
assembly was a rectangular affair with a squarish profile with a
blower at one end, and is designed for pass transistors for up to four
regulators. HSA1 and HSA2 each have the pass transistors for two -2.0V
regulators, HA3 and HA4 for four -5.2V regulators each, and HSA5 for
two -5.2V regulators, one of which was not used in any normal KL10
configuration.  All five HSAs and the control circuitry are attached
to a single rack mounting panel, which normally has a cover in place.
The HSA mounts are hinged for service access.

See for example assembly drawing E-UA-H761-0-0 for the complete
assembly, dated November 1974, and E-AD-7009404-0-0 and
E-AD-7009405-0-0 assembly drawings for the individual HSAs. These are
in the FMPS for the KL10A:
    http://www.textfiles.com/bitsavers/pdf/dec/pdp10/KL10/MP-KL10-A1_KL10_vol1_Sep75.pdf
I don't see a print set for the KL10B online, but I'm confident that
the H761 Regulator Assembly was the same.