Hi,
has anyone tried to write a paper tape emulator in BASIC? I've had a go in
GW-BASIC, but I suspect that the implementation of the language is too slow
to reliably drive the serial port - it doesn't always pick up the paper
advance signal (I've tried using both CTS and DCD as inputs).
Will I have to go to a machine code routine to get the fast port access?
I look forward to replies.
Jim.
Please see our website the " Vintage Communication Pages" at WWW.G1JBG.CO.UK
Hi All,
I picked up a Prime computer PDT-100 terminal, sans keyboard, today at
the auction. I have not (yet) started to collect Prime computer stuff,
so I anybody who want this, It's Free, just pay the shipping. I'm not
sure if it works OK, but it does power on!
Give me a shout off-list!
Cheers
Tom
Hi Guys (well OK - Tony mostly :-),
Started looking at the Compupro 8086 S-100 system this evening.
As usual during initial power tests - pulled all cards, and began
to power-up through variac and series light bulb - Bulb glows
brightly as power comes up, suggesting system is drawing far more
power than it should, and chassis voltages (+8, +16, -16) fail to
come up hardly at all.
After investigating, I discovered that there is a large capacitor
attached to a separate winding off the transformer. This is a
oval metal can capaciter (looks like a cylinder, except that end-
on view would be oval). It reads:
4 MF 660 AC 60 HZ
RONKEN P81A23405H01
Protected 900 AFC
NO PCB'S CONTAINS
FLAMMABLE FLUID
2483
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?)
I am reluctant to conduct a "full power" test as the light bulb
glows and full intensity if I bring the Variac up to 120v with
the cap connected - ie: the system is appearing as a very low
impedance load - when it should be drawing virtually nothing.
Ohm-meter tests of the CAP show that it is NOT shorted, and is
functioning as a capacitor (brief current flow when leads reversed).
It looks to me as if this Cap is acting as a low impedance load
at 60hz and effectively "shorting" the winding that it is connected
to, which causes the transformer to draw excessive power.
Can anyone explain to me what is going on, and why the unloaded
power supply is drawing so much on it's input? A brief tutorial
on how this type of supply is supposed to work would be very
helpful...
Regards,
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
On Apr 28 2005, 16:58, Brad Parker wrote:
>
> "Rick Bensene" wrote:
> ...
> >- A full set of drive select (0-3) plugs for RL01/RL02 drives
>
> Heh. I could use a "0" myself.
>
> What does one do when one only has a "1"?
>
> it works, but i'd like a 0. can I make one out of something else?
Look at the fingers on the "1" plug. The protruding finger on each
side has two edges which can be long or short, but one of those is just
used to tell the drive there's a valid plug inserted. A matchstick
makes an effective substitute :-)
A zero has short edges on upper and lower left, short on upper right,
intermediate on lower right (that last one is the "valid plug" finger).
A one has short edges on upper and lower left, long on upper right,
intermediate on lower right.
A two has short on upper left, long on lower left, short on upper
right, intermediate on lower right.
A three has short on upper left, long on lower left, long on upper
right, intermediate on lower right.
ISTR that when I made my own perspex plugs, before I had real ones
(other than a "zero"), I found there was no real difference between
"short" and "intermediate" -- "short" doesn't move a contact, "long" or
"intermediate" does.
--
Pete Peter Turnbull
Network Manager
University of York
I picked a new copy of the Digital VGB10 Video Terminal Installation and
Operating Information manual at the local Goodwill. It has all the pin outs
and is written in several languages.
Hi all,
I read the recent threads about S-100 hauls, so I'm putting out the request for a SRAM board for the Altair 8800 that I'm putting back together.
Just about anything is fine; 1K, 4K, 8K etc. As long as it's static ram, and will work with the original i8080 CPU. Can pay cash.
Thanks, Bill
--
---------------------------------------------
-. William W. Layer .- -. St. Paul, MN USA .-
---------------------------------------------------
-. Cheif bottlewasher, Atma-Sphere Music Systems .-
-. http://www.atma-sphere.com .-
--------------------------------
Hello fellow ClassicCmp'ers,
I have a Viewsonic PT813 21" CRT monitor, a very high-end professional model
that I was told used to cost $1800 new (1997), has both DE15 and BNC inputs
and supports both PeeCee video and sync on green. Unfortunately it is
malfunctioning - the picture is smudged to the point of being totally
unreadable. It seems like some component in its circuitry went bad -
I don't think it's the CRT - so it's probably fixable.
The person who sold it to me has agreed to refund me what I paid for it
and let me keep the broken monitor, and OKed me offering it for free to
the list. Since I believe it to be fixable, but lack the time, tools and
skills necessary to do so, I offer it for free to anyone who thinks he can
fix it.
If fixed it would make a great monitor for classic computers, and has the
added bonus that the VS3100 GPX board firmware is perfectly happy with this
monitor connected (as I wrote in my other posts, it often throws up a tantrum
with other perfectly good SoG monitors). So if you fix it, it should work
beautifully with VS3100 GPX, VS3100 SPX, other DEC and other classic
workstations.
The monitor is near San Diego, California. If you want it, you must come
and pick it up. I lack the materials and skills to properly pack it for
shipping (if I shipped it, you would get a pile of broken plastic and glass
instead of a bad-but-fixable monitor), and I don't even have a car to take
it to a shipping store that could pack it for me.
MS
>
>Subject: AIM 65 lives
> From: Andy Dannelley <andyda at earthlink.net>
> Date: Sun, 01 May 2005 10:15:59 -0700
> To: cctech at classiccmp.org
>
>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.
>
>First, before getting the help I found several stuck address lines and
>cleared them by blowing an brushing and vacuuming.
>
>We then found that 5 out of 8 2114 RAMs were bad, and the CPU just
>didn't have enough oomph.
>
>After cleaning the board and replacing parts, it works like a charm.
>Seems weird that the CPU and RAM went bad just sitting, and the board
>got something stuck in the address lines just sitting in the box for 20
>years, It was the original shipping box for the AIM, but I guess more
>crud got in the box than I realized.
People forget that plastic cased parts are not hermetic and therefore
subject to internal corrosion and failure.
The other is even assembled boards are susceptable to ESD damage.
The last is I have brough many boards with odd problem back to life
by running them through the dishwasher. I've seen odd failures due
to conductive grunge on the board that could not bee seen with
the naked eye.
Last some brands and styles of scokets really didn't stand the
test of time. I have a few NS* boards I've desocketed and soldered
the chips directly in becuase of that.
Allison
>
>Subject: Re: Free: broken but possibly fixable sync-on-green monitor
> From: Jim Leonard <trixter at oldskool.org>
> Date: Mon, 02 May 2005 15:25:48 -0500
> To: General Discussion: On-Topic and Off-Topic Posts <cctalk at classiccmp.org>
>
>Tony Duell wrote:
>> A word of warning to anyone who gets this... I had an Apple Mac+ that had
>> a smeared display -- shaddows to the right of objects on the screen. Now,
>> the Mac+ video circuit is pretty simple, but none-the-less I spent quite
>> a time going through it, unable to find the fault.
>>
>> The reason I couldn't find a fault in the video amplifier was that there
>> wasn't one. It was the CRT. Low emission, I think.
>>
>> Most of the time, a smeared picture _is_ a fault in the video amplifier,
>> though. But it may not be.
>
>I had a trintron tube connected to the same computer for 8 years slowly go
>"smeary" on me and I never found out why (monitor was on for only 3-4 hours
>each day, not 24/7). The "smears" were always after a high-to-low or
>low-to-high contrast (ie biggest voltage change) on the screen and were always
>in the direction of the scan (ie left to right, eventually fading out at the
>far right). Video card never failed once, and produced a perfect picture on a
>new monitor.
>
>So what caused that? What went "bad" over time to cause such a thing, and is
>it fixable?
Actually the most common thing I've seen short of a complete horizonal
output failure is the CRT focus pot and associated resistor string fails.
It's a gradual failure and for most color monitors that's part of the
HV transformer assembly. A few I'e stretched the life by adjusting
the focus but sooner or later it fails and the images are just plain
fuzzy.
I think currently I have 4 in the garage that have either focus
or horizonal output problems. Anyone wants to pick them up and
a few working tubes give me a email.
Allison
