>
>Subject: CV Transformer - Capacitor on separate winding ?
> From: Dave Dunfield <dave04a at dunfield.com>
> Date: Mon, 02 May 2005 21:34:21 -0400
> To: cctalk at classiccmp.org
>
>Disconnecting this capacitor "cures" the excess current draw and
>the chassis voltages come up fine (still running through variac at
>reduced AC voltage with series light bulb as I expect this cap is
>part of a "line voltage regulator".
>
>The transformer is labled "C.V." (Constant Voltage?)
The cap needs to be there. An unloaded CVT runs hot and draws
more current due to the highly reactive load. A side effect
of storing power in a resonant circuit (floating coil and cap).
As the transformer is loaded the current remains the same but
more stored energy is transfered to the active load. I have
a Compupro Chassis, TEI and even a spare supply of that style.
I also have 120V/120V CVT for systems that do not have one
internally. They tend to run warm under normal cases. It
should with a modest load (auto headlamps are handy for this)
behave and also not blow primary side fuse(s).
By current switchmode tech they are scary but represent old
magamp thinking and are reliable devices.
Allison
Nothing special, but interesting/amusing (somewhat):
20 YEAR OLD INCORPORATED COMPUTER SOFTWARE COMPANY
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=46685&item=751152187…
It's in Santa Barbara, California. Perhaps Marvin knows who this is?
--
Sellam Ismail Vintage Computer Festival
------------------------------------------------------------------------------
International Man of Intrigue and Danger http://www.vintage.org
[ Old computing resources for business || Buy/Sell/Trade Vintage Computers ]
[ and academia at www.VintageTech.com || at http://marketplace.vintage.org ]
>From: msokolov at ivan.harhan.org
>
>So if halon is really so benign, why did they ban it?
>
>MS
>
Hi
Like many things that were produced that were too
stable, it doesn't break down until it gets someplace
that it can cause problems. In its case, it would
cause problems of ozone lay decay. For the purposes
of putting out fires it worked well. It does produce
some nasty hydrofluoric acid when heated enough.
Early on, they tended to think that it was good
to make things that didn't break down easily. Things
like DDT and fluorocarbons were considered as the
greatest thing. Now days, people talk about recycling
and degradable.
Dwight
I've got a new bounty out. I'm looking for Desktop Express for the
Macintosh circa late 1980s. This was a package put out by Dow Jones to
enable you to retrieve stock quotes and graph trends on the display.
If you have a copy of this, it's worth some bucks to me. E-mail me
privately, please.
Thanks!
--
Sellam Ismail Vintage Computer Festival
------------------------------------------------------------------------------
International Man of Intrigue and Danger http://www.vintage.org
[ Old computing resources for business || Buy/Sell/Trade Vintage Computers ]
[ and academia at www.VintageTech.com || at http://marketplace.vintage.org ]
One of the UK pioneers - obituary as reported in The Times yesterday:
Andrew St Johnston, computer pioneer, was born on August 28, 1922. He died
on April 3 2005, aged 82.
Andrew St Johnston was one of Britain's computer pioneers. He led the team
which developed Elliott Brothers' 400 series computer, a machine which
introduced many features now taken for granted, such as modular
architectures and removable magnetic storage.
Andrew St Johnston took a degree in electrical engineering at the City
and Guilds College in London, then part of Imperial College. After
graduating in 1943 he joined the Navy and served as a radar officer, rising
to the rank of lieutenant-commander.
In 1949 he joined Elliott Brothers. A long-established British company
which had diversified from scientific instruments into control systems, it
was unusual among the early computer companies in that it made its own
machines, instead of developing models of computers produced in
universities. The 401, for which St Johnston was project leader, was run
for the first time in public at the Physical Society on April 22, 1953. At
the time Elliott computers were more popular than the early IBM models. St
Johnston then worked on the more advanced, transistor-based, 803.
His first marriage was dissolved and in 1958 he married Aldrina (Dina)
Vaughan, a programmer at Elliott's who had worked on the Cambridge EDSAC.
In 1959 she set up Vaughan Programming Services - it was Britain's first
software house, offering programs and support for other companies'
computers.
St Johnston joined Vaughan in 1966 when it had established a reputation
in control systems, warehouse automation and information display; it
provided passenger information services for airports and railways. In 1996
it was sold to Harmon, a US company in the same field. St Johnston and Dina
retired in 1999, after three years' running the renamed Vaughan-Harmon
Systems on behalf of its new owner.
In 1994 he and Dina donated an Elliott 803 to the Computer Museum at
Bletchley Park. Having spent ten years in a barn, it was restored to
working condition and remains on display.
>
>Subject: Re: CV Transformer - Capacitor on separate winding ?
> From: Dave Dunfield <dave04a at dunfield.com>
> Date: Tue, 03 May 2005 06:49:28 -0400
> To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at classiccmp.org>
>
>But I think you have provided the information I needed - normally
>I bring up a chassis with no load, initially at very low line voltage
>to allow the big electrolitic filter capacitors to take it easy as
>they reform.... But I've not encountered a resonant transformer
>design before - if I understand you correctly, not having any load
>at all is putting the transformer/cap into a state where it is drawing
>excessive power - I will try supplying a load. Do I need to load all
>of the windings, or will drawing from just the 8V supply be adaquate
>(I would expect the latter).
>
>Thanks,
>Dave
>--
Load the 5V one at least 10%. In actuality it makes little difference
if one or all of the winding are loaded as it's the load applied to
the core that counts.
Allison
>>Disconnecting this capacitor "cures" the excess current draw and
>>the chassis voltages come up fine (still running through variac at
>>reduced AC voltage with series light bulb as I expect this cap is
>>part of a "line voltage regulator".
>>
>>The transformer is labled "C.V." (Constant Voltage?)
>
>The cap needs to be there. An unloaded CVT runs hot and draws
>more current due to the highly reactive load. A side effect
>of storing power in a resonant circuit (floating coil and cap).
>As the transformer is loaded the current remains the same but
>more stored energy is transfered to the active load. I have
>a Compupro Chassis, TEI and even a spare supply of that style.
>I also have 120V/120V CVT for systems that do not have one
>internally. They tend to run warm under normal cases. It
>should with a modest load (auto headlamps are handy for this)
>behave and also not blow primary side fuse(s).
>
>By current switchmode tech they are scary but represent old
>magamp thinking and are reliable devices.
Thanks - yes, I figured the cap needs to be there, but removing
it during low power tests identified it as the cause of the high
current draw - I guess I was not clear on this as several people
have emailed me to warn me not to run it without the cap.
But I think you have provided the information I needed - normally
I bring up a chassis with no load, initially at very low line voltage
to allow the big electrolitic filter capacitors to take it easy as
they reform.... But I've not encountered a resonant transformer
design before - if I understand you correctly, not having any load
at all is putting the transformer/cap into a state where it is drawing
excessive power - I will try supplying a load. Do I need to load all
of the windings, or will drawing from just the 8V supply be adaquate
(I would expect the latter).
Thanks,
Dave
--
dave04a (at) Dave Dunfield
dunfield (dot) Firmware development services & tools: www.dunfield.com
com Collector of vintage computing equipment:
http://www.parse.com/~ddunfield/museum/index.html
-------------Original message:
From: Andy Dannelley <andyda at earthlink.net>
Subject: AIM 65 lives
>Just a note of thanks for help and encouragement. I finally got my AIM
>back running again with the help of a local who had some test
>equipment.
Congratulations! Sounds like ya had fun.
>Now the first thing I need to do is to get the 20 mil current loop to
>RS-252 working so I can use my Mac as a terminal and program
>development and storage.
Depending on your Mac's input sensitivity, it may work as is. The
AIM serial input (J1-Y) is RS-232 compatible (R24 should be 3K3; older
versions were only 1K). The output (J1-U) is of course TTL level which is
often adequate; if not and you've got +/- 12V available, an optoisolator
does the trick, otherwise a Maxim MAX233 is a convenient single-chip
solution.
I'll send you the relevant app note off-list.
mike
