Insurance company is paying to clean some of my "affected" gear. However,
they want me to get a price on just replacing the vt220 & televideo 950
instead of getting those two cleaned & ozoned.
I found one dealer selling refurb vt220 w/LK201 for $248USD. Anyone else
have a preferred source where I can buy either of the above?
Jay West
I have had my fun with Unix boxes but I think it's time to try something a little older and more complex.
I first thought about looking for an older IBM mainframe like the system/36 but my chances of finding one were pretty much slim to none so I then thought about the computers that DIGITAL made. Yes it would be fantastic to own something like a PDP-12 rack (how often do you see a bright green computer these days?) but knowing how my luck is almost never with me I would have to settle with something smaller. That returns me to my chances of finding a PDP. I live in Western Canada and so far it has been hard enough just finding a SPARCstation 1+ so I assume that something like a PDP will be even harder. How common are DEC's these days and where are they usually found and how much do they usually go for if any price at all?
It would be a rather nice (but late) christmas present to myself.
_________________________________________________________________
Read what Santa`s been up to! For all the latest, visit asksantaclaus.spaces.live.com!
http://asksantaclaus.spaces.live.com/
I have been looking for a readable copy of the schematic for this card.
It seems that the Harte Technology copy is all that's out there. The
schematic is real poor quality
Anyone have one they have scanned ????
Thanks, Jerry
Jerry Wright
g-wright at att.net
While the subject of delay lines has been hashed out here for a while, most of
the delay lines used in TV sets are probably not too reasonable for data
storage.
In particular those used in NTSC sets are to balance the delays in the chroma
circuits (those that are on the 3.579 sub carrier) with the luma signal (which
isn't processed). Since the chroma goes thru additional circuits, the other
signal needs to be delayed (not very long) to maintain the registration. In
PAL sets, I believe that the same idea is used. The difference is that in PAL
sets a different subcarrier frequency is used, and the demodulation products
are different for every other line (they swap In-phase, and Quadrature). SECAM
is a bit different, as they do NOT use in-phase and quadrature (simultaneous)
demodulation of the color difference signals, but alternate them line by line
(The 'S' in SECAM). This necessitates a one line delay to keep around the
other color difference signal to display on the line. More complexity in the
receiver with all that switching and "storing", and while it has lower color
resolution is more immune to phase differences which plague signal chains in I
& Q (NTSC/PAL) systems. PAL systems on the other hand with the swapping of I &
Q every other line (the 'A' in PAL) usually nulls out the differences.
If you decide to make up a delay line to hold CPU data, try a prototype using
shift registers. They are a bit easier to make up, and often the chips are
available. The problem is that they come in weird (at times) sizes (132, 80,
and the like). I'll leave it to the reader to determine the usability of odd
sizes and their original use.
--
Sorry,
No signature at the moment.
____________________________________________________________________________________
Never miss a thing. Make Yahoo your home page.
http://www.yahoo.com/r/hs
...don't you also need to *write* at the same speed? I'll bet
there's something in the design of the audio cassette heads that
makes it hard to do that.
I'm pretty firmly in the camp of (at least initially) abusing
technology by changing as few parameters as possible. That'd mean try
the experiment with a (or 8, but since it's a serial computer .... )
head mounted over a drum (or disc) that pulls tape past it at the
design speed for that head, 1 7/8 ips (?) for a cassette tape head.
That also implies the max. data rate will be something like the max.
bandwidth of the tape recorder, maybe 10 kHz. (Hey! Stereo recorders
will give you 2 bits parallel, at close to 18 kHz....)
Once you get it running at that clock rate and get the
distributed.net client compiled and running ( :-) ), then work on
speeding it up. I'd say the kewl factor on that machine will so blow
away anything I've ever done that you need not also have a MHz
advantage... Good luck!
At 9:43 -0600 12/14/07, cctalk-request at classiccmp.org wrote:
> > Very interesting project. Won't standard tape heads only work reliably if
>> the magnetic material's passing by at quite a narrow range of speeds,
>> though? Google suggests that's 1 7/8" per second, which isn't very fast at
>> all - a drum that can do a few tens of RPM seems possible, but 6000??
>
>I don't think it makes a difference. The higher the speed, the larger the
>voltage from the flux transition, but that shouldn't be a problem (within
>reason). The head gap and medium speed dictates the "resolution" of the
>system. You can think of it as being like trying to write with different
>sizes of pen nib.
>
>Look at reel-to-reel audio recorders - they may run at a variety of speeds,
>giving a tradeoff between audio quality and recording time. You can use a
>higher flux density with a larger head gap (and a correspondingly larger
>drive signal), but you need to haul the tape through faster to maintain the
>bandwidth.
>
>On playback, you get the problem that higher frequencies produce a higher
>voltage, hence the need for equalisation (not unlike the RIAA curve for
>magnetic record pickups).
>
>In this case you probably just want to detect the presence or absence (or
>possibly polarity) of a pulse. Equalisation won't be a worry.
--
- Mark, 210-379-4635
-----------------------------------------------------------------------
Large Asteroids headed toward planets
inhabited by beings that don't have
technology adequate to stop them:
Think of it as Evolution in Fast-Forward.
I am probably the original source of that manual, and actually the manual is
quite good .... except for the schematic. That probably reflects how the
schematic in the manual actually was. I have two other files that contain
the schematics for the 64FDC in a better quality format. One is a 24MB
multi-page TIFF file (not too many readers can read multi-page TIFF files),
the other is an adobe acrobat pdf file produced from the TIFF file which is
a 6-page pdf file and it's only 720k in size. The 24MB TIFF file was
scanned from an original at 600 dpi, and the pdf file, not withstanding that
it's only 5% as large, seems to have retained the quality of the tif file.
Barry Watzman
Message: 3
Date: Wed, 26 Dec 2007 04:31:27 +0000
From: g-wright at att.net
Subject: Cromemco 64FDC manual, needed
To: cctalk at classiccmp.org (cc_talk)
Message-ID:
<122620070431.15702.4771D91E000F3A4900003D5622193100029B0A02D29B9B0EBF9B0809
079D99D309 at att.net>
Content-Type: text/plain
I have been looking for a readable copy of the schematic for this card.
It seems that the Harte Technology copy is all that's out there. The
schematic is real poor quality
Anyone have one they have scanned ????
Thanks, Jerry
Jerry Wright
g-wright at att.net
The H-120 was a generic designation for the "all-in-one" version of the
Heathkit / Zenith Data Systems Z-100 series of personal computers (actual
units had a slightly different model number depending on their
configuration). It was a dual processor system, 8085 and 8088, could run
both CP/M and MS-DOS (but it was not PC compatible at the hardware level).
It had a large motherboard that included a 5-slot S-100 expansion backplane
at the rear. The system was available both in kit form and assembled, the
assembled models carried Zenith Data Systems rather than Heathkit labels but
were identical. The kit was mostly pre-assembled, only the floppy disk
controller and video monitor deflection boards were actually build by the
buyer, otherwise the kit was just a final assembly task of factory assembled
& tested boards.
The system had a floppy disk controller that could support both 8" and 5"
drives simultaneously (I think four 8" and three 5" drives). A hard drive
controller was also offered that could support two MFM hard drives.
Video came from a dedicated video board that was, for it's time, quite
sophisticated (the PC had nothing better until the EGA cards came out). It
was pure bit-mapped color graphics, 640x225 resolution.
There was a major revision of the motherboard after about 2 years of
production, the early models had a 5MHz 8088 and 3 banks of 64k each (192k
total) memory, the later models COULD (but did not always) have an 8MHz 8088
and the memory banks could be 256MB chips per bank (768MB total) rather than
64k per bank. Models with the late motherboard (85-2806) could be upgraded
to the faster CPU or larger memory if desired by changing some parts. The
early motherboard (85-2653) could not be easily upgraded (plans for
upgrading the early motherboard do exist, but it is a MASSIVE undertaking in
terms of the number of changes, cuts and jumpers required. It takes a real
masochist to undertake it).
Barry Watzman
[One of the architects of the Z-100 and the computer Product Line Director
for both Heathkit and Zenith Data Systems from 1979-1983].
Date: Wed, 26 Dec 2007 04:31:27 +0000
From: g-wright at att.net
Subject: Cromemco 64FDC manual, needed
>Content-Type: text/plain
>I have been looking for a readable copy of the schematic for this card.
>It seems that the Harte Technology copy is all that's out there. The
>schematic is real poor quality
>Anyone have one they have scanned ????
>Thanks, Jerry
>Jerry Wright
>g-wright at att.net
-----------------
Marcus also has an excellent collection of Cromemco manuals at:
http://maben.homeip.net/static/S100/cromemco/cards/index.html
but it looks like his is the same scan as Howard's.
They're good scans; it's the original that's bad. I'll look around to see
if I've got a different revision of the manual which might be better.
There were also a number of revisions and mods, depending on which
CPU it was used with.
Just curious: why do you need it?
mike
a laptop p/s would be ideal. Anyone offhand know which
lt's used 16 volts? Many thanks.
____________________________________________________________________________________
Looking for last minute shopping deals?
Find them fast with Yahoo! Search. http://tools.search.yahoo.com/newsearch/category.php?category=shopping
On Wednesday 26 December 2007 01:00:34 pm cctalk-request at classiccmp.org wrote:
Hi,
It was not so much a complaint on my part but rather a observation. I run and
own several web hosting companies so I know the difficulties involved. :-)
I get mail from this list in digest form so there is some lag in getting
notifies.
> Someone has already confirmed that it was a planned outtage. Just to make
> sure you don't miss this message I have CC'ed it to you.
>
> Sellam confessed to not doing a good job at communicating the planned
> outtage, but it should be back up again soon once all the data is
> transferred to new servers :)
--
Kindest Regards,
Francesca Smith
"No Problems Only Solutions"
Lady Linux Internet Services
Baltimore, Maryland 21217
