Recently I got a nice and complete PDP-8/s from the US. The power supply
uses a ferroresonant transformer which in addition to the standard primary
and secondary windings has a separate 2.3H winding connected in series to a
2uF 660VAC capacitor forming a resonant "tank" circuit. The transformer's
secondary side and the resonant circuit are operated in saturation. There
is a magnetic shunt to prevent the primary side going into saturation as
well. It accepts a wide input voltage range, but is very sensitive to the
input frequency of 60Hz. This is quite a nice if not elegant design for the
period in question, but maybe not the most efficient.
As I live in Australia I get 240VAC and 50Hz as opposed to the US 115VAC
and 60Hz.
I can easily convert our 240VAC to 115VAC with a step-down transformer, but
cannot easily supply 115VAC at 60Hz. So I was considering using a step-down
transformer to get the 115VAC, but modify the resonant "tank circuit" for
50Hz.
Unfortunately there is some magic I don't understand. The resonant
frequency of a LC circuit with L=2.3H and C=2uF is about 75Hz not the
expected 60Hz.
Otherwise I could just solve the standard LC resonant circuit formula for C
and plug in 50Hz and 2.3H to get the required C.
Obviously ferroresonant transformers are more complex than this former
software engineer can grasp. Could any experienced EE with relevant
transformer knowledge please chime in and help me understand how to
redimension the tank circuit to use 50Hz instead of the original 60Hz input.
Obviously I could replace the entire power supply with two modern switch
mode supplies to create the two rails, but it would be really nice to keep
the original supply and just reversibly adapt it for 50Hz.
Thanks and best regards
Tom
So, I may just be spoiled from using RSX11M-PLUS and now expect too much
from the RSX11M OS. But it seems to me the CLS command would be a
nice-to-have, but I am not able to find anything about it. So did that not
exist for RSX11M? How does one clear the screen in that environment?
-Peter
https://www.raspberrypi.com/products/rp2350/
From postings, I know that folks use the RP2350 for interfacing; the trade press has been shipping news of RP's rev A4 datasheet in volume.
The datasheet should tell all. However, the 5V tollerance of the "IO" pins is significant for its simplification of TTL interfacing; the maximum supply and output voltage remains 3v3. See section 14.8.2 (p 1335) et seq - NB the FT indication.
Martin
I tried to contact rsts.org using their web site form, but it threw a
server error when I tried.
I have two pieces of info for them, if they hang out here:
1) The files at
http://www.rsts.org/autoindex.php?dir=distros/RSTS_tapes/V_10.0/ and
http://www.rsts.org/autoindex.php?dir=distros/RSTS_tapes/V_10.1/
cannot be downloaded: access Forbidden error.
2) I have a product code for the RSTS 10.0 distribution tape (they say
"Unknown DEC Product Code" on the index page.)
The code on the actual tape is BB-P016P-BC RSTS/E V10.0 INSTALL 16MT9
(Unfortunately, my tape has not yet responded to my attempts to read it
- I think the signal that ought to tell the drive it is 1600 BPI PE
isn't being recognized by my HP SCSI tape drive - it thinks the tape is
800BPI, but it works OK with other 1600BPI tapes.)
JRJ
Hello,
I am a collector of old computers and a fellow owner of Datamaster
computers.
I have seen your CCMP post about wanting to have image output from your
5324.
I imagine this computer hasn't been serviced. If you want I could help you
to solve both issues.
If you still have the computer and want to do something with it, we would
first need to diagnose and repair it if necessary. I would guide through
the entire process of troubleshooting.
After the service, I would instruct you how to get video output through
HDMI.
Regards,
Jaume
Hi all,
I just spotted an auction on eBay for 40 IBM SMS cards.
It sold for over $2,000 (!)
Does anyone know if this reflects collector value or the value of the
gold content?
Also, what’s the current value of a set of SMS cold contacts?
Thanks,
Henk
www.ibmsystem3.nl
Greetings,
Been a long while since i have posted in on here. I usually discuss my pdp 11 and vax systems. I have decided to pivot my career to scada syatems. The company i am with has some interesting stuff that goes pretty far back. Our custom in house tech is a plc pump controller with a radio connection for data logging and control. Pretty cool, 8051 based, with a version of basic in rom that has scada functions added. The backend servers are just linux systems, although in a modular backplane for easy replacement.
I have not read much about this tech outside of what we have in house. Are there other historic scada system computers or technologies that are similar, easily found on ebay for example?
Ive seen some mention of old allen bradley stuff, but not much notes on how it would be used remotely in the field, as a remote terminal unit.
Any suggestions are appriciated, trying to read more into scada tech outside of my company's tech.
Thanks,
Devin D.
Honeywell made a large number of these systems, which were in use in
many industries (oil refining, manufacturing of all types, water utility
distribution, etc.). They were quite expensive, and PLC manufacturers
have made great inroads into that market in the past couple of decades.
As a result, some of that equipment is showing up in the surplus market.
I found a Honeywell "Orion" console desk being disposed of that I would
have loved to take, except that it was truly massive (it must have
weighed nearly a thousand pounds!). It was electrically height
adjustable (with memory), had mounts for two very large monitors,
integrated lighting, cable management, and rack spaces for physical
buttons and lights. Actually, a lot of their equipment is pretty
massive, especially when compared to current-day PLCs.
~~
Mark Moulding
There's been discussion of this on the VCFed forum, but it doesn't look
like anybody's brought it up here yet. Per Mike Brutman, list member
Chuck Guzis a.k.a. Chuck(G) passed away recently. He was highly
knowledgeable, a full-bore storage expert, and an all-around even-keeled
decent sort, and will be missed.
