[I've not been reading the list for a little while, so apologies if this has
been mentioned already]
The Harwell Dekatron Computer - aka. WITCH - has just arrived at TNMoC for
restoration. Once completed, it'll be (as far as we know) the oldest
functional, complete, stored-program electronic machine in the world (some
careful qualifying there, because of course it's one of a handful of
'pioneering' machines, all of which have their place in history).
Lots of links to news items on the machine at:
http://www.tnmoc.org/inthenews.aspx
Plans for the machine date from 1949, with it first running in 1951. Wikipedia
background info at http://en.wikipedia.org/wiki/WITCH_(computer)
cheers
Jules
> Date: Thu, 03 Sep 2009 15:32:25 -0500
> From: John Foust <jfoust at threedee.com>
>
> Late 80s, early 90s IDE drives don't show up on the IDE-to-USB adapters
> I'm using for other applications these days.
This may not apply to your case but...
Remember that old Western Digital drives will not work unless you use the
"Single" jumper setting on the drive. Setting them to Master in a
single-drive setting does not work.
For that matter, did you set the Master/Slave/Single jumper? Older drives
are also less likely to work with Cable Select.
Jeff Walther
> From: Jules Richardson <jules.richardson99 at gmail.com>
> Subject: Another "oldest computer" story...
>
> [I've not been reading the list for a little while, so apologies if
> this has
> been mentioned already]
>
> The Harwell Dekatron Computer - aka. WITCH - has just arrived at
> TNMoC for
> restoration. Once completed, it'll be (as far as we know) the oldest
> functional, complete, stored-program electronic machine in the world
> (some
> careful qualifying there, because of course it's one of a handful of
> 'pioneering' machines, all of which have their place in history).
>
> Lots of links to news items on the machine at:
>
> http://www.tnmoc.org/inthenews.aspx
>
> Plans for the machine date from 1949, with it first running in 1951.
> Wikipedia
> background info at http://en.wikipedia.org/wiki/WITCH_(computer)
The relays look similar to the ones my 1301 uses to switch the signals
to the front panel indicators and peripheral interlocks (so mine only
switch at human speed). Even the markings on the relays look very
familiar. I hope they are more reliable than mine though, as the
machine seems to be using them for actual computations. I suppose they
would be fine with routine maintenance, usually consisting of dragging
a bit of punched card between the closed points.
Roger Holmes.
>>> If this is acting up, for testing purposes it would seem to be safe
>>> to remove it to see if the voltage changes (jumps back to around
>>> 12V) ?
>> No, that would remove all regulation from the 12V rail.
> If wired per the reference in the PDF... for testing with no devices
> attached (will prob need a dummy load for 5V I'd imagine) to see if
> the part is what is causing the voltage to drop to 8.5V. Not to
> actually use.
I still wouldn't do it, some SMPSs can self destruct without feedback.
> This is also a small part... wouldn't it be dissipating a large amount
> of current clamping the rail from 12+V to 8.5V?
No, it's not used as a clamp like that. The 12V will be divided down by
some R and the pot so that normally 2.5V would be on the REF pin. The
K pin then sinks current that is the feedback to regulate the voltage.
This is often the LED side of an optoisolator.
> I have an ESR meter.
So do I. I wish I'd got one years earlier with the effort it has saved
since.
> Have you ever seen a cap 'leak' oil?
I've seen all kinds of strange substances leak out of caps including
oil, wax and what looked and felt like oily, grey cotton wool.
> but I've never seen a semiconductor device leak 'oil'?
Some RF power modules are mineral oil filled but I've not seen it in
a discrete device.
> Guess I'll have to plan on pulling the caps to see if they could
> be the source of the leak....
I'd measure ESR first then only pull random caps if nothing showed
up.
> but if so... I'd imagine they should have a film on them too, no?
It depends, it may have evaporated from around a hot capacitor. If
that's where it came from.
> And of course they have that white 'glue' between them (more like
> a hard caulk than glue I guess ?).... what is that for anyway ?
Mostly to annoy me I think.
Lee.
> Anyone got any ideas as to the oily film ?
Most likely it is from a capacitor.
> If this is acting up, for testing purposes it would seem to be safe
> to remove it to see if the voltage changes (jumps back to around 12V) ?
No, that would remove all regulation from the 12V rail.
You can test this part out of circuit. Connect REF to K, pins 1 and 3 on
the TO92 part, and these two to +5V through a 680 or 1K ohm resistor.
Connect A, pin 2,to ground. With the 5V on you should read 2.495V +/-2%
between K and A.
This part can be replaced by a TL431, LM431 or equivalent.
> So, suggestions, ideas on the film, and best way to go about
> troubleshooting the 12V rail are welcome :-)
An ESR meter to test caps is pretty much essential. Some obviously
fail but others can look fine but still be high R. Electrolytics
are by far the biggest single cause of switch mode supply failure.
Lee.
Hi All.
I'm taking my first stumbling steps into the world of VAXen and VMS.
Before I sink my teeth in the bigger machines I have, I've decided to
see if I can get my VAXStation 4000/90A to run.
It seems mostly okay, I can boot the VMS cd I have. But there is one
message that concerns me. During the self test I get this:
?? 000 8 SYS 0512
That last number is not hex, if I type the following
>>>show err
I get
?? 000 8 SYS 0200
And I guess 0200 is hex.
Either way, in the manuals I have found, I can read that the test for
device number 8 is checking the systems ROMs and that this indicates a
checksum or read error. The error code shown is not listed in the
manuals. Should I worry about this? Can it be remedied?
Kind Regards,
Pontus.
So, the problem with my OKIStation is the power supply.
5V is solid... but 12V was only putting out 8.5 volts (with
no drive load attempted... unsure if the motherboard uses
12V for anything).
I have found there is an adjust for 12V, I have not touched it
as of yet. In getting that far, that small pot, 2-3 resistors, a
3 legged "IC1" (NEC C1093) and that area of the PCB have an light
oily film on them. The IC1 and the little pot seemed the worse.
I'm not sure what this could be... I've never seen a transistor/IC/
etc emit an oily film... I can't see it coming from the trim pot, and
even though there are a few nearby capacitors... they don't have a
film on them.... and I've only seen capacitors ooze brown scum.
If there are no failing components, then either the trim pot has
gone dirty... or that "oil" ? has got into it and is causing it to
ohm out wrong.
As there is no way I'd find another of these supplies, my only option
is to fix it.
Anyone got any ideas as to the oily film ?
Looking up IC1 on the net I find
http://pdf1.alldatasheet.com/datasheet-pdf/view/6668/NEC/C1093.html
which indicates it is an adjustable precision shunt regulator. In the
test and application circuit section of the pdf, this device goes across
Vout. If this is acting up, for testing purposes it would seem to be safe
to remove it to see if the voltage changes (jumps back to around 12V) ?
The oily film puzzles me...
I don't see any sign of bad caps... and this power supply seems to be
well engineered (has temp probes on the switching transistors presumably
to shut down the supply should things get too hot).
Being a three board supply design with several connections soldered ...
it hasn't
been a joy to get apart this far :-)
So, suggestions, ideas on the film, and best way to go about
troubleshooting the
12V rail are welcome :-)
Thanks,
-- Curt
I am looking for information for my recently acquired ASR33 that has
an Anderson Jacobson modem (ADT-233) built into it. I have retrieved
the documents for the base ASR33 from Bitsavers and University of
Queensland, but it doesn't look like any of the manuals describe the
modem. The modem is complete with the acoustical coupler. :-) The
modem does have a Teletype sticker on it and describes it as a UCC-6.
I need to know how to hook the ASR33 to my PDP-11 using a 20mA
connection. I am looking for user guides, technical details and
schematics.
Thanks!
--barrym
At 05:06 PM 9/3/2009, feedle at feedle.net wrote:
>> And they'll correctly identify and mount an elderly IDE that
>> doesn't specify its geometry when queried?
>
>No, they won't. I've personally even had problems with modern on-board
>IDE not working with older drives.
Has anyone ever seen a USB-to-IDE adapter that can handle the old drives
and devices, presumably by allowing you to specify the Cyl/Hd/Sec?
After reading http://en.wikipedia.org/wiki/Parallel_ATA , I'm surprised
to see that although IDE drives appeared in the late 80s, the ATA-1
standard didn't arrive until 1994.
Based on the chart there, I'm guessing that today's USB-to-IDE devices
(as well as near-recent onboard IDE) simply don't support the old PIO
transfers and only handle the post-1998 ultra DMA transfers?
- John
