Who's rewired their house for this hobby?

Eric Smith spacewar at gmail.com
Wed Nov 26 14:28:13 CST 2014

On Wed, Nov 26, 2014 at 11:35 AM, Jon Elson <elson at pico-systems.com> wrote:
> On 11/26/2014 01:47 AM, Eric Smith wrote:
>> 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.
> Not true!  The CPU was, absolutely, a KL10B.  It was in a big orange cabinet
> that was
> fairly similar in size and shape to a VAX 11/780.  It had a PDP 11/40 (I
> think) in the
> next bay over as the I/O processor.  I am not so clear about the exact
> "DECSystem"
> designation, but it VERY much was a DECSystem 20<something>.

As I said, it's not a 2020, and if it's any other model of DEC 20,
it's a KL10-C,
KL10-E, or LK10-ER.

You might be confusing the "Model B" designation (multiple section,
vs. "Model A" which is single section) with the KL10 suffix, but
they're not the same thing. A 2040 or 2050 can be either Model A or
model B, but are the KL10-C, KL10-E, or KL10-E/R hardware models.

The "Model A" means that the logic assembly inside the KL10 is a
KL10-PA, while "Model B" may be KL10-PV or KL10-PW:

Marketing                  software    Full KL10  KL10 CPU
Designation               "model"     P/N          logic assy
---------------------------     ------------    ------------    -------------
DECsystem-1080       Model A   KL10-A      KL10-PA
DECsystem-1090       Model A   KL10-B      KL10-PA
                     *or*      Model B   KL10-D      KL10-PV
DECsystem-1090T     Model A   KL10-BC    KL10-PA
DECsystem-1091       Model B   KL10-E/R   KL10-PV
DECsystem-1095       Model B   KL10-E/R   KL10-PW
DECSYSTEM-2040    Model A   KL10-C      KL10-PA
                     *or*      Model B   KL10-E      KL10-PV
DECSYSTEM-2050    Model A   KL10-C      KL10-PA
                     *or*      Model B   KL10-E/R   KL10-PV
DECSYSTEM-2060    Model B   KL10-E/R   KL10-PV
DECSYSTEM-2065    Model B   KL10-E/R   KL10-PW

The KL10-R was the FCC-compliant version of the KL10-E.

> OK, the thing was all on one huge fan, but there were dozens of power
> transistors on
> individual heat sink segments, all arranged in a circle around the fan.  So,
> yes,
> there were several regulators, electrically, but the main pass transistors
> were all
> mounted in a single unit.

Totally contrary to every KL10 I've ever seen, and all the published
maintenance documentation.  There's an individual fan on each heat
sink, and they are arranged in a rectangular fashion.  I really don't
believe that DEC built a special version just for you.

> Yes, if you don't go the
> Seymour Cray route and run EVERY DAMN SIGNAL differential from one board to
> the
> next, then you do have to be careful that the power supplies are fairly well
> matched.

It's not a matter of timing, though that was a concern too.  If they
used a single big regulator, the voltage to each part of the backplane
would be different, and ECL has very low noise margins relative to the
supply voltage, so it won't work reliably. They have separate
regulators each with independent remote sense, and special provision
for handling a failure of remote sensing to prevent the ECL from being

>> I don't see a print set for the KL10B online, but I'm confident that
>> the H761 Regulator Assembly was the same.
> No, I think there was an "early" version and a "late" version.  The system

Both the KL10-A (earliest version) and the KL10-E/R (lastest version)
used exactly the same H861 regulator assembly.

> was not greatly different, but they reduced the number of separate regulators and I
> think cut one whole regulator board out of the system that way.

They never eliminated any ECL regulator board.  All KL10s have nine
5.2V regulators and four 2.0V regulators. The only thing eliminated
was the tenth 5.2V regulator, which was never used in any KL10 model.

I've owned a KL10-B, which had been upgraded to a KL10-D, and a
KL10-R.  I'd take pictures of the regulator assemblies of both, but
I'm about 1500 miles away from them.

I also hung out with the field service guy for the Colorado School of
Mines KL10-A in my misspent youth.

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