Thanks Tondy. I was hoping to hear from you on this matter. I'll see if I
can find a suitable replacement
- Mike: dogas(a)leading.net
-----Original Message-----
From: Tony Duell <ard(a)p850ug1.demon.co.uk>
To: Discussion re-collecting of classic computers
<classiccmp(a)u.washington.edu>
Date: Friday, September 10, 1999 5:50 PM
Subject: Re: CRT replacements for NS Advantage???
>>
>> Help!
>>
>> I just had a Northstar Advantage shipped to me and because of the shoddy
>> packaging job, the CRT is history. The back of the tube is broken. I'm
sad
>> and I'm pissed. I hate seeing equipment so mishandled.
>
>Ouch!!!
>
>
>>
>> Are there any compatible organ doners out there or suggestions for a
>> possible revival?
>
>There is no way you'll repair the original CRT if the glass is broken (or
>even cracked).
>
>Fortunately, there appear to be only 2 common flavours of monochrome CRT
>used in terminals/monitors. One type has a 8 pin B8H base (like an
>International Octal with thin pins and a large spigot), a thick neck, and
>a 6.3V heater. The other has a 'modified B7G base' (like a 7 pin
>miniature tube/valve, but with a hole in the middle of the socket to take
>the seal-off tube of the CRT), a thin neck and a 11-12V heater. Most such
>CRTs (of both flavours) have a 90 degree deflection angle.
>
>If you can get a suitable tube of the same class (perhaps raid it from an
>old terminal, like a VT3xx that's blown its flyback, or raid it from a
>cheap portable B/W TV), it's likely to work. You may have to fiddle the
>electrode voltages slightly, but in my experience, putting the CRT in,
>fitting the original yoke (these are _not_ generic), and pluging in the
>base and EHT cap will produce a useable image.
>
>-tony
>
The score narrows, but I can't claim a complete victory....
Tony wrote...
>Well, if the servo can lock the heads in both directions, then the power
>rails are probably OK (although it can't hurt to check them). Your next
>job (and I can't help here as I don't have the schematics) is to figure
>out how it unloads the heads (where does it apply the unload signal, what
>causes it, etc) and then to check through the electronics. It's not that
>complex.
I went through the schematics, concentrating on the PMR board (Power
regulator) and Drive control board. Not in great detail, but just enough to
get a general gist of the sequence of events and "who does what". I then
went down and checked the disc power supply (it's a separate rackmount
unit). Then before starting to follow traces and wires I decided to pull all
the connections from the rest of the system to the PMR board. I was
specifically looking for wires that had come loose, or pins that weren't
pushed all the way in the connector, etc. Double checked that my hand
written labels on the connectors (done before removing them) showed that all
the connectors were back in the right place.
Powered the drive up - heads seeked and drive ready came on. Hit the unload
switch, and the heads immediately retracted and the brake engaged. Did this
about 10 times in a row, every time the heads retracted nicely just like
they're supposed to. Hummm... this leads me to one of two possible
conclusions: A) there was just a loose connector, or B) this is a total
co-incidence that it started working and the problem might very easily
happen again. Now that it's working, further troubleshooting to be sure of
the exact cause is not easy. I Know I had all the connectors pushed down
firm and in the correct place before, but, it does work now (at least 10
times anyway, my luck the 11th time would have been the failure).
Followup questions:
1) The drive innards are dusty again, must be the environment (or running
with the covers removed didn't help I guess). What is the best way to get
all the dust out? Canned air doesn't begin to get the dust off the plastic
surfaces, neither does a DP-style vacuum. Any tips/tricks anyone would care
to pass on?
2) From the previous spin-down with the heads on the platter, the bottom
heads are mint but the top heads now have oxide streaks on them. Cleaning
with foam qtips and IPA doesn't budge any of it. I am loath to take out the
top heads (removable platter) and send them out for recontouring and
test-fly because then the drive will need to be re-aligned and I don't have
an alignment cartridge (and probably the know-how) to realign them. This is
only important because I have a diagnostic cartridge that I need to be able
to read for additional cpu/disk/tape diagnostics on down the road. Is it the
general consensus that heads in this condition are ok to use or am I setting
myself up for a major problem. What I'm hoping is on down the road to get
the diagnostics copied from cartridge to 1/2 tape. Then I can send the heads
off and not bother with re-alignment (other than having to reformat my
cartridges and lay data from tape back down. Bad idea?
Thanks!
Jay West
Or look at http://www.calpoly.edu/~darkjedi/300/00.htm for a twisted view of
the incident.
Or, to quote my Mother, the people responsible for this disaster "should be
flogged with a maggoty cat"!
My 2 cents: relying on S/W for safety is like relying on timing for birth
control.
I've known of beatifully made Swiss molding machines with all sorts of
hydraulic and electrical interlocks still closing at 100 tons force an inch
>from someone's fingers.
Give me a 2 inch steel bar anyday.
Neil Morrison
Implementation
GTE Enterprise Solutions
ph: (604) 293-5710
email:morrison@t-iii.com
> -----Original Message-----
> From: CLASSICCMP(a)trailing-edge.com [SMTP:CLASSICCMP@trailing-edge.com]
> Sent: Thursday, September 09, 1999 1:59 PM
> To: Discussion re-collecting of classic computers
> Subject: RE: therac-25
>
> > I found myself in the mood for revisiting the macabre side of
> >classic computing and decided to search for Therac stuff. See:
> >
> >http://www.dcs.ed.ac.uk/~adamd/essays/rts3.html
> >
> > Now it seems to me that the fellow who wrote this article was
> >pretty full of it. If you can get past his overuse of passive voice and
> >continual nominalization, you may note that many of his points are far
> too
> >theoretical and not supported by direct observation, knowledge, etc.
>
> It's clear (to me, at least) that he's never directly worked with
> any of the Therac machines, nor did he even bother talking to the
> folks at AECL before writing his article. It's entirely a bunch of
> opinions of his after he read Nancy Leveson's article on Therac.
>
.... clipped
Thanks Tony and Joe!
Just before dinner I powered up the drive again. After the 30second spinup,
the heads move out to cylinder 0 and the drive ready light comes on.
I tried very gently moving the head assembly both forward and back. The
thing wouldn't even think about moving. I applied more pressure (a pretty
fair amount IMHO), and the head assembly still won't budge at all. I hit the
unload switch and the drive starts to brake, but the heads don't retract. I
immediately move the heads back manually and all is well (at least no
further HDI).
After dinner I'll start double checking the power supply voltages. Thanks
for any and all input!
Jay West
I found myself in the mood for revisiting the macabre side of
classic computing and decided to search for Therac stuff. See:
http://www.dcs.ed.ac.uk/~adamd/essays/rts3.html
Now it seems to me that the fellow who wrote this article was
pretty full of it. If you can get past his overuse of passive voice and
continual nominalization, you may note that many of his points are far too
theoretical and not supported by direct observation, knowledge, etc. For
example, he claims that this [perhaps] regenned rt11 monitor supports
multi-threaded execution to the degree of its enabling things like race
conditions, etc.
Hindsight is 20/20, I guess...
just throwing it out there as discussion bait...
jake
Guys:
I just got a stack of software for the Xerox 8010.
It is the Viewpoint O/S (v.2.0), office productivity
tools, fonts, converters, etc. Six boxes of
8" floppies. This includes what appears to be
the install disk set for the VP O/S itself.
If interested, please send offers via private E-Mail.
Thanks.
Jeff
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In a message dated 09/08/1999 10:16:10 PM Eastern Daylight Time,
allisonp(a)world.std.com writes:
> Oh, I forgot one. There's a program called "checks" that can be found on
> the WC CDrom and the OAK.oakland.edu archives. Runs nicely on the kaypro.
> Theres a lot of messydos and CPM software out there in the archives
waiting
> to be used.
Thanks for pointing me to this site! This is going to keep me off the
streets and out of trouble for a *long* time!
Glen Goodwin
0/0
Here are the current exhibitors at VCF 3.0:
Charles Notley
Shift Reset - Heathkit H89
Doug Salot
Early Toy Computers
david dameron
Conway's Game of Life
Wayne M.
IBM 5100 Model B2 and Peripherals
Dwight Elvey
4004 Developement System
Dwight Elvey
Single Plywood Board Computer
Tom Belpasso
First CMOS uP with homebrew FORTH
Jim Willing
PDP-8/e - EDUSystem 25 TimeShared BASIC
Jim Willing
Altair 8800 - MITS TimeShared BASIC
Jim Willing
Heathkit Educational RObots
Mike McManus
Osborne Shelly
John G.
MUNIAC
Hans Franke
Der Sozialismus ist unaufhaltsamm
Michael Kan
Real-Time Software Bench Testing environment
Liza Loop
The First Apple I and Other Highlights of Early Microcomuputers in Learning Environments
Jordan Ruderman
Exhibit - Sol
Jordan Ruderman
Sorcerer
Jordan Ruderman
Osborne III
Derek Peschel
Marchant model ACR8M calculator
Larry
Commodore PET 2001
What will YOU be bringing to exhibit?
http://www.vintage.org/vcf/exhibit.htm
Sellam Alternate e-mail: dastar(a)siconic.com
------------------------------------------------------------------------------
Don't rub the lamp if you don't want the genie to come out.
Coming this October 2-3: Vintage Computer Festival 3.0!
See http://www.vintage.org/vcf for details!
[Last web site update: 08/17/99]
I wrote:
<< > I even have a couple of business apps (Tony Duell, don't gag ;>) which I
run
> on my Sinclair machines . . . just crank up the old imagination, Jim, and
Tony Duell replied:
> Hmmm... Sinclair microdrives were known for being WORN (write once, read
> never) units, so I do have problems trying to run a business from one of
> those machines. Oh well... >>
Not a _business_, but a couple of non-critical business apps. And, yes, the
microdrives are horribly unreliable. I'm using a third-party drive i/f and a
DSDD 5.25" drive for storage. The i/f was developed (and is still
supported!) by a fellow here in the States. I get 450 KB out of each
diskette, which suits my needs ;>)
Glen Goodwin
0/0
