I wouldn't call the TK-81 a "mix-up". Google the Timex/Sinclair 1500.
Al
----- Original Message ----
From: "Alexandre Souza" <alexandre-listas at e-secure.com.br>
Since I wrote about the brazilian apples, I'll write a bit about the
brazilian mix-up clones.
A "mix-up" is a clone with a whole different cabinet, copied from
another computer.
Here we go:
TK85 (microdigital) - ZX81 with 16K and some circuit enhancements,
Cabinet from Sinclair Spectrum
Eric J Korpela <korpela at ssl.berkeley.edu> wrote:
> On Thu, Apr 23, 2009 at 1:04 PM, Warren Wolfe <lists at databasics.us> wrote:
>> > That many
>> > orders of magnitude of complexity have come and gone since the IMSAI days
>> > are good, in terms of what one's money will buy today, but bad in that one
>> > is much less likely to be able to fix one's own equipment to component
>> > level. It's not as satisfying to say "Hmmm. You need a new video card" as
>> > to hold up the offending transistor and cackle. Or is that just me?
>
> Maybe I'm seeing this from a different angle... I don't see a lot of
> difference besides the complexity of the devices. A transistor is a
> device that you buy because you can't make one yourself without
> spending way too much money. A video card is essentially the same
> thing. You can make one yourself. Some day we will be forced to in
> order to keep our machines running. The main difference is that the
> theory of operation of a transistor can be expressed in a 1 page
> document. The theory of operation of a video card is a small book
> that requires references to other books.
And herein is a big problem. People today don't even know what a
transistor is.
The difference compared to a video card is huge, but you need to know
all this to understand that.
Yes, you can build your own transistor. It isn't difficult, and it isn't
expensive (well, compared to a transistor I guess it might be, but we're
still talking close to no money). All it requires is two diodes. That's
all it is, really.
A transistor (and now I'm just talking about bipolar transistors, since
it's the easiest, and they are very common) is extremely simply to
understand and build.
But why do that when someone have already done it for you?
The big point, however, is that a transistor is very small, extremely
cheap, and easily replaceable. A video card have none of those
attributes, and that's the real point here. You can't "fix" a video
card. You replace it. Whatever is build with discrete transistors
however, can be fixed. If the transistor breaks, you replace it.
Fixing a video card is extremely difficult at best, and in the future I
suspect that will be a lost cause. Fixing whatever item made of discrete
components will easily be done a 100 years from now, I dare say.
Johnny
--
Johnny Billquist || "I'm on a bus
|| on a psychedelic trip
email: bqt at softjar.se || Reading murder books
pdp is alive! || tryin' to stay hip" - B. Idol
>
>Subject: Re: What kind of IC is this
> From: ard at p850ug1.demon.co.uk (Tony Duell)
> Date: Wed, 31 Dec 2008 22:50:52 +0000 (GMT)
> To: cctalk at classiccmp.org
>
>> > If you're lucky, eitehr th microcontroller is old enough not to
>> > have any
>> > security features, or they're not used. In which case you remove
>> > the chip
>> > from the PCB and stick it in a suitable programmer.
>>
>> Even the original Intel 8051/8751, circa 1980, has security
>> bits. :-( There are ways to get around (at least) those, though.
>
>Yes, but IIRC the 8048 series (common in classic computer stuff) doesn't...
>
>-tony
My fractional portion of currency is that the 630x is a hitachi varient of the
680x (6800 single chip mpus). I've seen and have some them from older hard
disks and DC300 tape drives that had mechanically expired.
Allison
> From: ard at p850ug1.demon.co.uk (Tony Duell)
> Subject: Re: The General Approach to Computing - A Ramble
>
>> And, while I like playing with the old computers, and fixing them,
>> nothing beats screaming speed in a personal computer.
>
> Now that's something that's never bothered me .If my machine takes 10
> minutes to complie my program, so what? I just do something else while
> it's compiling. And it gets me to check my code before compiling it,
> hopefully ending up with a etter program (the 'poke and hope' brigade
> worry me -- changing things until the program compiles and/or runs)
It depends on the size of the program. I work on a a program which
used to have a million lines of source code and on a 2GHz Intel
MacBook Pro takes around 10 minutes to compile for debugging. Building
the final version on our PowerPC server for two target architectures
take a good half hour.
You can imagine how long it would take to compile on my 1301 where the
shortest instruction (NOP) is 12 microseconds and the longest
(multiply with both operands of 12 non zero digits) is 3784
microseconds.
I have recently constructed an RS232 interface for my 1301 (Just a
level changer and one bit input the processor can sample, no fancy
UART or SCC) and using a USB to serial converter on the Mac have
connected the two. A six instruction bootstrap hand keyed into Flossie
(my 1301) and a download and go high level assembler in the Mac mean I
can write software whenever and wherever I happen to have a few
minutes free. Back at home I can power up Flossie and usually find the
core memory still contains my bootstrap, then assemble and squirt the
program down the serial port at 9600 baud, which wouldn't take long,
even to load the entire 2000 words (48 bits) core store. So far my
biggest program is only about two hundred words. When I fill the core
I'll have to start overlaying off drum or tape, or even Mac when I get
serial output working too.
I am hoping to retrieve software from about 100,000 punched cards via
the check reading brushes of the card punch, which is much more gentle
on old cards than the real card reader. Then it will be time to start
on the programs on magnetic tape, but first I have to get a higher
speed parallel interface working so I can read the tapes without
stopping between blocks and risk stretching/breaking 40 year old tapes.
I have been looking into getting the line printer working. There are
120 off 100 microfarad 100v capacitors which hold the energy required
to fire the print hammer solenoids. Each on is about an inch diameter
and three inches long. The modern equivalent is tiny and will not even
reach between the holes in the PCB, but the leads can be extended. Of
course they don't look right, maybe I should think about opening the
old cans and putting the new components inside. Maybe there are
harmful chemicals inside.
When a transistor or diode fails I don't have the option of buying new
ones, but fortunately I have ample spares of used ones of most types.
Most times I can replace the whole card (four AND gates, one flip
flop, one inverter and re-inverter, a clock gate or dozens of types of
amplifiers/attenuators). Occasionally the fault is with the wiring or
wire wrap or soldered joint. All these are very reliable but there are
literally millions of them so the odd one failing is not really
surprising.
Core failures are a totally different problem. The official method is
to use a spare row or column which has worked fine so far though long
term I am worried about running out. I don't think my eyesight would
be up to remaking a whole core plane but one day it might be necessary
to get it done.
I enjoy the intellectual task of finding the location of a logic fault
but not mechanical problems, they are just something which has to be
done, a pain in the backside.
I purchased an 820-II from eBay, but the seller did a horrible packing job
and it arrived with the case completely smashed.
Incredibly enough, the CRT was not shattered and once I diassembled it and
spread things out, it nominally fires up. I get the monitor sign-on and a
beep, but no keyboard response at all.
I've already tried reseating everything on the system board and fixed a
bad solder joint on the crystal for the keyboard MPU. No luck.
I have some schematics from the web, but they are extremely fuzzy and hard
to read. Can anyone help with theory of operation for an 820 keyboard?
I gather that it's a parallel data interface, but past that I'm a bit in
the dark.
I should mention that I'm running without a disk drive. The seller "lost"
it and I have the carcass of another on the way from a kind cctech group
member. Still, I would think there'd be some response to keyboard input
without the drive on line.
Steve
--
A few new documents are up under http://bitsavers.org/pdf/intel/MDS2
including the service manual (which unfortunately has two sheets missing
which describe part of the IOC board). Clean copies of the schematics are
there, though.
Jim Battle <frustum at pacbell.net> wrote:
> Johnny Billquist wrote:
> ...
>> > It isn't difficult, and it isn't
>> > expensive (well, compared to a transistor I guess it might be, but we're
>> > still talking close to no money).
>
> Maybe it is possible to build a transistor that has poor gain, low
> bandwidth, and poor stability, probably like the first transistors made.
>
> Jeri Ellsworth built some FETs and simple gates at home -- but she said
> it took two years to figure out how to make it work, and she needed some
> equipment (like vacuum chambers) that few people have at home. It was
> far from simple.
>
> http://trail.motionbased.com/trail/episode/view.do?episodePk.pkValue=8067618
>
> Yes, that is a FET, not bipolar. If you have some links for making
> simple bipolar transistors, please supply some. It will make for some
> interesting reading.
>
> I recall reading how IBM spent a lot of money and a lot of brainpower
> building their own transistors back in the early days. If it really was
> all that simple, I doubt that IBM would have wrestled with it as much as
> they did.
I purposely picked bipolar since they're easy. I haven't looked at what
it would take to make a FET. Don't think it's that relevant to reply
with stuff about FETs to a post about bipolars. :-)
>> > All it requires is two diodes. That's
>> > all it is, really.
>
> If you wire two diodes in series (PN->NP), it isn't the same as a
> transistor (PNP), at all.
It is. A PNP is just the same thing as a PN-+-NP.
The things left that vary is the areas between the PN and NP layers,
which would be equal if you just jused two diodes, but usually are
dissimilar in a transistor. That can be solved by using different
diodes, or putting two in parallel.
What else? Yeah, the amount of doping is also relevant. All this ends up
to is that different transistors have different specs (just as different
diodes do). You'd hardly replace a transistor with a couple of diodes on
a card anyway, since it would be so much trickier soldering wise, and
possible space wise anyway, not even considering characteristics. But
that don't change the fact that you get a working transistor with just
two diodes.
>> > A transistor (and now I'm just talking about bipolar transistors, since
>> > it's the easiest, and they are very common) is extremely simply to
>> > understand and build.
>
> I've heard of people disassembling a diode and making a point contact
> transistor, but that is already leveraging a lot of technology that put
> the $.10 diode in your hand to begin with.
Well, I did say that you'd have to use diodes. If you consider it
cheating to use diodes, then I plead guilty. It's very difficult to make
a transistor if you're only allowed to use copper, aluminium and silicon.
However, all this was just an exercise in sidetracking. The real point
was that something built with transistors can be repaired by just
replacing the transistor. A very standard, small and cheap component
that you probably still can get a hundred years from now. A graphics
card will never be at that situation. If it's broke, you replace it. Ten
years from now, that will not even be an option, since those graphics
cards are no longer manufactured, and even the bus which they interface
to is probably obsolete, meaning no other graphic card can be found
either. And it is not possible to repair it, since it's just a bunch of
highly intergrated ICs on it, which you cannot obtain, nor diagnose
which one of them actually is busted. They are also close to impossible
to remove.
Johnny
--
Johnny Billquist || "I'm on a bus
|| on a psychedelic trip
email: bqt at softjar.se || Reading murder books
pdp is alive! || tryin' to stay hip" - B. Idol
I inherited a HP Designjet 500PS.
It has earlier in it's life a magenta printhead explosion... so was a
mess inside
(nobody bothered to properly disassemble and clean the printer....
Did that, including disassembly and reassmbly of the service station.
However, yellow stopped working... so it can't align print heads.... so
I picked
to primed tubes... but that needs a set of setup printheads that I don't
have....
and I can't get out of that step even with a power cycle.... couldn't try to
'clean' the heads either.... as it needs to align the heads first ...
which fails as
yellow is not printing.... so I've gotten myself into a realy catch 22
situation with
it....
And now I'm stuck w/o setup print heads.
So, does anyone have or know where to cheaply get a set of setup printheads
for a designjet 500, 500PS, 800, or 800PS (should all be the same). A
replacement
ink tube spare part would have the carts as well.
This is the 25" variety, but other than the spare ink tube kit being
different for
25" vs 42", the setup printheads would all be the same.
Anyone have a service station... this one fails sometimes when it tries
to ratchet
the big wheel on the left side of the service station...
Could also use a set of print heads.
Thanks,
-- Curt
>From: Vernon Wright <vern4wright at yahoo.com>
>Subject: Re: Ciarcia's Circuit Cellar
>
>I've built a number of Steve's projects. In my workshop a few days ago I
saw his EEG project >waiting to be revived.
I was the prime instigator in the HAL-4 project. When I lived in CT I was a
member of the CT Computer Club with Steve. He was always looking for ideas
for his monthly column. Being a psychologist (but almost EE major) I had
worked with biofeedback and thought a low cost EEG unit would be cool. I
wrote the specs for the hardware and software and the non-technical parts of
the article while 2 other club members did the hardware and software
respectively, and Steve Many hundreds of these kits were sold over the
years - I know because I enjoyed a $3/unit royalty on each one :-)
Never-before-revealed-fact: I spec'd the design to have two switches which
the operator could use to signal awareness of up to 3 internal states to see
if they could be correlated with the brainwave pattern. In fact, I was
inspired by Tim Leary's 'experiential typewriter' which he speculated could
be used similarly when he first started experimenting with LSD.
Brainwave feedback and analysis have progressed greatly in the past 20+
years and there's no reason why the PC software couldn't be re-written,
though not many people have a serial port to which to connect HAL. I
suppose an inline serial USB converter could be used.
I believe there is still open source hardware specs and description
available on the web.
Bob Stek
Former Saver of Lost Sols
(On topic, as NCSA Mosaic was killed in 1997.)
So, I have nothing to do on weekends except sit on highway overpasses and
snipe cars with a high powered rifle. Because of the terms of my probation,
I had enough time this weekend in Corcoran to work on this:
http://www.floodgap.com/retrotech/machten/mosaic/
This is another update of NCSA Mosaic, based on 2.7b5. I started with that
and fixed a couple seriously crippling bugs for 2.7ck6, and in this version
2.7ck7, there are more improvements to the HTML core, fixed a lot of bugs
with Gopher support, and cleaned up the source so that it would also compile
under Mac OS X.
There is a Universal binary for 10.4+ (requires X11 and OpenMotif, download
links are on the page), plus source, and source builds on Power MachTen and
most versions of OS X in general. If people build this successfully on other
systems like Linux, *BSD, etc., I would like feedback.
I'm considering porting this to A/UX next, but I will not have access to
A/UX in San Quentin, so I'd better hurry up.
--
------------------------------------ personal: http://www.cameronkaiser.com/ --
Cameron Kaiser * Floodgap Systems * www.floodgap.com * ckaiser at floodgap.com
-- I had amnesia once -- or twice. --------------------------------------------
