You guys and your hobbies. I was lucky enough as an engineering co-op to work with a microVAX pdp11 running the VMS OS, networked with a microVAX II that ran our main data acquisition software, communicating over GPIB with HP3852 A/D converters and PSI8400 devices. We upgraded to 1GB hard drives in 2005! Original hard drives were 640MB and had to be locked down when we transported the 4 that we owned into a single location for turn-in. We had reel-to-reel backups and TD-50 cassettes as well. It was really fun to make changes in software, (written in Fortran 77), and really see the functionality go to work. I support wind tunnels in the research environment and I really miss the days of running tests on a mere few megabytes. Now I can develop software that acquires data at 200kHz over 48 channels without a hiccup across a CAT6 network using NI hardware. I still own power supply Heath kits and meters from the 1970s that I use for Elec-trak component troubleshooting, along with iPod and iPhone repair, lol.
-----Original Message-----
From: CZ Unit <cz alembic crystel com>
To: elec-trak <elec-trak cosmos phy tufts edu>
Sent: Sat, Jun 14, 2014 11:38 pm
Subject: Re: (ET) Controllers
On 6/14/2014 6:18 PM, Robert wrote:
> CZ,
> I fix old watches too, a Hamilton 992B anyone? Computers from the 80's,
> how about an HP71B, I still have one and use it along with lots of
> programmable HP RPN calculators like the mid 80's 11C (which is still
> going strong in my machine shop). I think it's not that those old
> computers broke, it's that they got obsoleted by software and newer
> technology. There are guys still looking for old stuff, I built a
> Sinclair in the late 70's that I later sold, nothing wrong with it, just
> outdated.
Very nice. Most of my work is on the Elgins; I have an 1871 era slow
train HH Taylor model and it's quick-train peer the BW Raymond. The
Taylor is cased in 18k gold. You can always tell because the case is
dented; clad cases will not dent, real gold will. Likewise I'm restoring
a pdp8/e right now, much simpler than the older 8I I had 20 years ago.
By the 1970's they got a lot better about making a 50 pound supply
instead of a 100 pound supply (yes, I am powering it with a Corsair/500;
working on a 12 to 15 volt DC-DC converter)
> As for reversing the field, think about it, how were they going to
> reverse the field back then? With an 'H' bridge circuit, not then they
> weren't. The relay was the easiest and probably most reliable solution.
The right way to do it was to lock the field on and reverse the
armature. That's what they did on the E20, and I think the E20 came
before the E15. Also why the original E12 had a 3 speed version of the
E20 control without field weakening.
I thought the E15 came a bit later as a reduced cost model. It had fewer
main speeds (3 vs 4) and less field weakening and the dopey card
controller. The E12 started out with the armature control then seemed to
move to the E15's type of controller.
C
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