Sports! .. and with an on-topic association.
ard at p850ug1.demon.co.uk
Wed Dec 22 13:37:13 CST 2010
> > A quick look at the picture of me on the recent HPCC conference page
> > (linked from http://www.hpcc.org/ ) will, I think indicate that I am
> > not the wort of person to go running...
> Okay, the caption of the second picture is: "Tony Duell described the
> HP9836CU Desktop Computer; he took it apart, displayed circuit diagrams
> (on the wall in the background) and showed and described each component
> Looking at that pile of parts begs the question: Why doesn't the
> caption include the phrase "and put it back together again?"
Becasue I didn't. Not as part of the talk anyway...
However, for those who are now worrying about the fate of a fairly
interesting classic computer, don't!. The photos on the web site are in
chronological oprder, and in the photos of Hugh Steers' talk you can see
an HP9836C (you can't tell it's a CU, but you can see the second mains
lead to the monitor, so it must be the colour monitor version). Since
this was taken after my talk you have to conclude that either somebody
else brought suich a machine to the meeting or that I did, in fact, put
it togther again.
I will explain
This has become something of a tradition at HPPC conferences. I take
along a somewhat off-topic machine (an HP desktop calculator or computer)
which most of the members will not have seen and then demosntrate it,
take it apart, and describe some aspects of the design. I always arrange
for my talk to be given jsut before a tea/coffee break. After the talk,
members of the audience cna come and look at the bits of the machine,
talk to me, take photographs , etc. And during that time I put it all
back toghether and test it again.
 I don;t mind people taking pictures of me or the machines using any
equipment with the exception of flashpowder (or flashbuttons). I don;t
want everytthing covered in MgO :-)
Actually, there was one minor differenece in the 9836 talk. Becuase it
has a stange monitor interface (22kHz horizontal scan rate I think, and
current, not voltage, drive for the RGB signals), it couldn't be easily
linked to a video projector and thus I didn't consider it possible to
demonstrate it before the audience. Instead, I had it running over the
lunchbreak (I had a hard disk with HP BASIC 5.1 on it with me...) and let
people program it or try out some of the demonstration programs.
There are a few thigns that might not be obviosu fro mthe photos. In the
first picture, there are 2 objects on the table othe than the machine
and a roll of tools. The diecast box is a home-made tester for the PSU
board in the 9836. The PSU consistes of an unregualted 30V (or so) PSU
mounted in the case with the output wirted to an edge connector and a
regulator PCB that plugs into this connector and also into the
motherboard. The test box takes the PSU regualtor PCB (in the 2 edge
connectors on top), takes in 30V or so from my bench supply, and provides
dummy load resistors, monitoring lamps, and test socksts for the 3 output
rails. There's a significant amount of logic on the motherboard,
including a progammed microcontroller for the keyboard, so I don't want
to risk that if I suyspect there may be PSU problems.
The little circuit board in the first photo is a similar device for
testing the SMPSU in the colour monitor. It plugs into the backplane
connector of the monitor PSU, you connect the PSU to the mains and apply
12V to the cable comming fro mthe test board. The 12V supply operates the
mains relays in the SMPUS, it should then come to life. And on the test
board are load resisotrs, monitor LEDs and testpoints for the monitor PSU
In the second picture (the one your commenting on), you can see the test
box again. The binder in front of it is just the schematic for the 9826,
9836A and 9836C machines (these 2 machines have a lot in common). The
long probe-thing on top of the toolkit is a Heathkit EHT meter, which I
use to check and diskcharge the CRT anode connector (yes, there is a
bleeder resisotr, but 25kV is unpleasnat and I'd rather be safe than
sorry). Because as you can see from the far left of the picture, I did
remove the CRT from the monitor.
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