20 Aug
2006
20 Aug
'06
8:30 a.m.
I've got a ZX80 here (issue 2A) which has a keyboard overlay attached that
looks very like that of a Sinclair ZX81.
The ROM in the machine is dated week 16 of 1981, and carries the marking
C77018, and a 1981 copyright.
Is this a machine that's been subjected to a ZX81 upgrade kit or something? I
wasn't aware that such a thing existed.
Now, the keyboard overlay's actually removable, revealing a pristine original
ZX80 legend underneath. However, two black press-fittings attach it to the PCB
at the corners of the front edge - are these press fittings there on all
ZX80s, or have these been added in order to secure the overlay in place?
The machine came with a "ZX 16K RAM" module (red lettering) which I assume is
later and more in keeping with a ZX81? Separately though I do have a module
marked as "ZX80 16K Byte RAM Pack" (white lettering). Question is, are they
interchangeable and the lettering was altered - or does the ZX80 variant map
memory to a different location than the later red-lettered type? (I'm assuming
that the expansion bus pinouts didn't change between ZX80 and the later machines!)
I've also got a ROM marked as: "ROM contents copyright 1980 Sinclair Research
Ltd" - is this the original ZX80 ROM (and the ROM in the machine is an
upgrade), or is this likely something else entirely?
Curiously there are a few stray fibres glued to the underside of the PCB -
presumably these are a left-over of cheap PCB manufacture and Sinclair's
horrible quality control! :-)
cheers
Jules
--
A. Because it destroys the natural flow of conversation.
Q. What's wrong with top posting ?
20 Aug
20 Aug
7:59 a.m.
At 13:30 20/08/2006, Jules Richardson wrote:
Is this a machine that's been subjected to a
ZX81 upgrade kit or something? I wasn't aware that such a thing existed.
Yes. Keyboard overlay and new ROM was common
about the time the ZX81 came out, for all those
who had just stumped up ?100 for the ZX80 (there
was only a year between them..)
I have a ZX80 with ZX81 ROM but sans
overlay... (It actually is a ROM for a ZX81, and
works fine with the exception of 'SLOW' (i.e., no
flicker) mode. The hardware is basically the
same. (And no ZX80 ROM that I can find..)
Now, the keyboard overlay's actually removable,
revealing a pristine original ZX80 legend
underneath. However, two black press-fittings
attach it to the PCB at the corners of the front
edge - are these press fittings there on all
ZX80s, or have these been added in order to secure the overlay in place?
Without getting mine out and checking, ISTR that
the ZX80 came with a plastic push-plug thingy at
each case corner to hold it all together. If you
have just just this, going through the corner of
the keyboard PCB and locking it to the case
underneath, then it's probably original.
The machine came with a "ZX 16K RAM" module
(red
lettering) which I assume is later and more in
keeping with a ZX81? Separately though I do have
a module marked as "ZX80 16K Byte RAM Pack"
(white lettering). Question is, are they
interchangeable and the lettering was altered -
or does the ZX80 variant map memory to a
different location than the later red-lettered
type? (I'm assuming that the expansion bus
pinouts didn't change between ZX80 and the later machines!)
ZX RAM packs were completely interchangeable, the
pinout, and the memory allocations were the
same. I think ROM mapped to 0-16K, RAM at 16K+
The "original" RAM pack for the ZX80 was a thin
affair in the same construction (plastic covers
either side of a small PCB with push pins to hold
together) which held up to six socketed
2114's. You could buy in various memory
configurations, and add the extra 1K, 2K or 3K as required yourself.
The 16K RAM packs I think only came out at the
time of with ZX81 and were dynamic RAM. (The
originals were all static.) I think Sinclair
branded 'ZX80' (rather than ZX or ZX81) packs are
quite rare, as the ZX81 ones worked just
fine. There were lots of third party RAM packs
aimed at the ZX81. - I had a 32K one, plus an
extra ROM board that gave me lots of fancy
alternate graphic characters.. (mapped to the
8K-16K region, in place of a mirror of the system ROM)
I've also got a ROM marked as: "ROM contents
copyright 1980 Sinclair Research Ltd" - is this
the original ZX80 ROM (and the ROM in the
machine is an upgrade), or is this likely something else entirely?
Highly likely that it's the original ZX80 ROM ... try it!
Curiously there are a few stray fibres glued to
the underside of the PCB - presumably these are
a left-over of cheap PCB manufacture and
Sinclair's horrible quality control! :-)
no idea; never had mine apart that far .. It may
be whomever upgraded it had it apart at one point
too, and these got picked up then?
Rob
10:24 a.m.
Rob O'Donnell wrote:
Yep, there are five larger white plastic clips holding the case together, then
two smaller black ones for the overlay - it does indeed look like the PCB was
pre-drilled for these, so I assume that they're present even on an ZX80
without an overlay. I was just thinking that I'd rather take the machine back
to ZX80 spec, so not having extra holes drilled in things as part of the
upgrade is a bonus :-)
:-) It does seem to be the original - BASIC keywords are mapped to the ZX80
keyboard layout, whereas with the other ROM they map to the slightly different
layout of the upgrade overlay.
They look more glued 'into' the PCB though. At first I thought it was just
stray junk and was about to clean them off - but if it was like that from the
factory I'll leave them as-is :-)
That machine works, anyway, after a fashion - but I can't get a nice clear
picture on the couple of TVs that I'd tried so far, so it's possible that
there's a fault in the modulator somewhere. But it's evidently OK otherwise
and doing things as expected... (I *think* I've got a spare UM1233 somewhere
if I can find it, in which case it'll be easy to swap it in and try it)
Out of interest, anyone know how many ZX80s were sold as kits? This one's a
factory-built one, complete with original ZX80 PSU. The heatsink for the
regulator gets pretty hot, and that's even without the RAM pack plugged in...
cheers
Jules
At 13:30 20/08/2006, Jules Richardson wrote:
Thanks - not something I'd heard about before. I've had a couple of ZX81s in
the past (later ones, issue 3 and 5 I think) but never had a real look at a
ZX80 before.
Is this a machine that's been subjected to a
ZX81 upgrade kit or
something? I wasn't aware that such a thing existed.
Yes. Keyboard overlay and new ROM was common about the time the ZX81
came out, for all those who had just stumped up ?100 for the ZX80 (there
was only a year between them..) Now, the
keyboard overlay's actually removable, revealing a pristine
original ZX80 legend underneath. However, two black press-fittings
attach it to the PCB at the corners of the front edge - are these
press fittings there on all ZX80s, or have these been added in order
to secure the overlay in place?
Without getting mine out and checking, ISTR that the ZX80 came with a
plastic push-plug thingy at each case corner to hold it all together.
If you have just just this, going through the corner of the keyboard PCB
and locking it to the case underneath, then it's probably original. ZX RAM packs were completely interchangeable, the
pinout, and the memory
allocations were the same.
That's good to hear!
The 16K RAM packs I think only came out at the time of
with ZX81 and
were dynamic RAM. (The originals were all static.) I think Sinclair
branded 'ZX80' (rather than ZX or ZX81) packs are quite rare, as the
ZX81 ones worked just fine.
Interesting. Just whipped the lid off this one and it is DRAM as you say (8 x
4116 ICs).
I've also
got a ROM marked as: "ROM contents copyright 1980 Sinclair
Research Ltd" - is this the original ZX80 ROM (and the ROM in the
machine is an upgrade), or is this likely something else entirely?
Highly likely that it's the original ZX80 ROM ... try it! Curiously
there are a few stray fibres glued to the underside of the
PCB - presumably these are a left-over of cheap PCB manufacture and
Sinclair's horrible quality control! :-)
no idea; never had mine apart that far .. It may be whomever upgraded
it had it apart at one point too, and these got picked up then? 
9:51 a.m.
Jules Richardson <julesrichardsonuk at yahoo.co.uk> wrote:
Out of interest, anyone know how many ZX80s were sold
as kits? This one's a
factory-built one, complete with original ZX80 PSU. The heatsink for the
regulator gets pretty hot, and that's even without the RAM pack plugged in...
Mine was sold as a kit, but came assembled! They had run out of kits
and giving those who had paid for a kit the pre-assembled ones. I was
slightly disappointed. This was at the end of the ZX80 era right before
the ZX81.
I did a google search and looked on Wikipedia but some of the details
there do NOT match my memory. They say there were only 50,000 ZX80's sold
and this seems to be a ridiculously low number for a mass-market
machine sold through many different channels. They say that the Sinclair
brand was only in the UK and this does not match my experience of having
bought one in the US (or the
ads in 1980 Radio-Electronics). But this was 26 years ago, so my memory
isn't exactly sharp either!
The Wikipedia article might make sense if one assumes that it is
only talking about the UK and ignoring sales in the rest of the world.
My guesstimate, backed up by no FACTS at all but mostly on the machines
extreme cheapness and how many were eventually stacked up on store
shelves (there came to be a real glut of them after the successors
hit the market and they were being sold at local drugstores for circa
$50 when marked down), is that counting the US market, ZX80 sales were
in the low hundreds of thousands and that kits might have been 10
or 20 percent of the total.
Tim.
11:34 a.m.
Tim Shoppa wrote:
Jules Richardson <julesrichardsonuk at
yahoo.co.uk> wrote:
That is a shame - I imagine to a lot of people the aim was the fun in
assembling a kit, rather than the cost saving...
Out of interest, anyone know how many ZX80s were
sold as kits? This one's a
factory-built one, complete with original ZX80 PSU. The heatsink for the
regulator gets pretty hot, and that's even without the RAM pack plugged in...
Mine was sold as a kit, but came assembled! They had run out of kits
and giving those who had paid for a kit the pre-assembled ones. I was
slightly disappointed. This was at the end of the ZX80 era right before
the ZX81. I did a google search and looked on Wikipedia but some
of the details
there do NOT match my memory. They say there were only 50,000 ZX80's sold
and this seems to be a ridiculously low number for a mass-market
machine sold through many different channels.
I think you're right and that only applies to UK machines; other sites I've
seen suggest that the total number produced and sold worldwide was over 100,000.
It's interesting how rare they seem to be considering those sales figures - I
mean there are plenty of other machines around where sales were only a
fraction of that and yet there's still a healthy number in private hands.
cheers
Jules
--
A. Because it destroys the natural flow of conversation.
Q. What's wrong with top posting ?
10:45 a.m.
New subject: data sheet for com5025
Hi
Does anyone have a pointer to a data sheet for a com5025? I believe
it to be a synchronous serial chip but I've not found much on the web.
I think it is compatable with a 2652 but the only thing I can find on that
is a 16 bit part from Philips. I don't think this is a 16 bit appliction.
Thanks
Dwight
2:34 p.m.
New subject: data sheet for com5025
On Aug 20, 2006, at 10:45 AM, dwight elvey wrote:
Does anyone have a pointer to a data sheet for a
com5025? I believe
it to be a synchronous serial chip but I've not found much on the web.
I think it is compatable with a 2652 but the only thing I can find on
that
is a 16 bit part from Philips. I don't think this is a 16 bit
appliction.
The COM5025 is mostly compatible with the 2652, but not completely.
Both are 16-bit parts. I have info about it in a book here...My
scanner is having problems so I can't scan it, but I can type stuff up
from the book if you need it. Let me know.
-Dave
--
Dave McGuire
Cape Coral, FL
2:57 p.m.
New subject: data sheet for com5025
On 8/20/2006 at 2:34 PM Dave McGuire wrote:
The COM5025 is mostly compatible with the 2652, but
not completely.
Both are 16-bit parts. I have info about it in a book here...My
scanner is having problems so I can't scan it, but I can type stuff up
from the book if you need it. Let me know.
Isn't the Mostek MK5025 a compatible part? IIRC, it can be used on either
an 8 or 16 bit bus.
http://www.tranzistoare.ro/datasheets/restul/502155_DS.pdf
I've also got the 7990 Lance datasheets in printed form, which is
supposedly also compatible.
Cheers,
Chuck
3:18 p.m.
New subject: data sheet for com5025
Here's the 2652 data sheet, which looks to be quite different from the
MK5025
http://pdf1.alldatasheet.com/datasheet-pdf/view/19132/PHILIPS/SCN2652AC2A44.
html
5:15 p.m.
New subject: data sheet for com5025
On Aug 20, 2006, at 3:18 PM, Chuck Guzis wrote:
Here's the 2652 data sheet, which looks to be
quite different from the
MK5025
http://pdf1.alldatasheet.com/datasheet-pdf/view/19132/PHILIPS/
SCN2652AC2A44.
html
The docs I have here say the COM5025 was intended to be compatible
with the 2652, or at least mostly so, for both hardware and software.
A cursory glance at the pinouts shows them to be the same except, I
think, pin 1. I haven't looked at any of the programming info.
-Dave
--
Dave McGuire
Cape Coral, FL
21 Aug
21 Aug
10:09 a.m.
New subject: data sheet for com5025
From: Dave McGuire <mcguire at neurotica.com
On Aug 20, 2006, at 3:18 PM, Chuck Guzis wrote:
>Here's the 2652 data sheet, which looks to be quite different from the
>MK5025
>http://pdf1.alldatasheet.com/datasheet-pdf/view/19132/PHILIPS/
>SCN2652AC2A44.
>html
The docs I have here say the COM5025 was intended to be compatible with
the 2652, or at least mostly so, for both hardware and software. A
cursory glance at the pinouts shows them to be the same except, I think,
pin 1. I haven't looked at any of the programming info.
-Dave
--
Dave McGuire
Cape Coral, FL
Hi Dave
This must be the right one. The schematic I have shows a jumper option
to either a plup or +12v, on pin 1.
Dwight
12:48 a.m.
New subject: data sheet for com5025
From: "Chuck Guzis" <cclist at
sydex.com>
Here's the 2652 data sheet, which looks to be quite different from the
MK5025
http://pdf1.alldatasheet.com/datasheet-pdf/view/19132/PHILIPS/SCN2652AC2A44.
html
Hi
It looks like this is the part. I just didn't realize that it could
be a 16 or 8 bit bus connection.
Dwight
20 Aug
20 Aug
6:55 p.m.
New subject: data sheet for com5025
I've also got the 7990 Lance datasheets in printed
form, which is
supposedly also compatible.
Given that one is a synchronous serial chip, the other an ethernet
controller, I find that unlikely!
However, I have seen a 48 pin 5025 that has much the same pinout as
(IIRC) the 7900 -- well, one ethernet chip anyhow. Somewhere I have a
communciations bridge that can take 3 I/O cards. On the mainboard you fit
an 7990 for positions where you have ethernet cards, and a 5025 for the
X21 or X25 cards. I think there's a jumper to set too, but that's it.
-tony
9:23 p.m.
New subject: data sheet for com5025
On 8/20/2006 at 11:55 PM ard at p850ug1.demon.co.uk wrote:
However, I have seen a 48 pin 5025 that has much the
same pinout as
(IIRC) the 7900 -- well, one ethernet chip anyhow. Somewhere I have a
communciations bridge that can take 3 I/O cards. On the mainboard you fit
an 7990 for positions where you have ethernet cards, and a 5025 for the
X21 or X25 cards. I think there's a jumper to set too, but that's it.
Yup, that's essentially what the MK5025 datasheet says: "Nearly
pin-compatible with the Lance chip (MK7990)". Which is a curious use of
the term "compatible"--i.e. the signals are almost the same, the chip
functionality is not.
Strange but true.
Cheers,
Chuck
21 Aug
21 Aug
12:08 a.m.
New subject: data sheet for com5025
From: "Chuck Guzis" <cclist at
sydex.com>
Reply-To: "General Discussion: On-Topic and Off-Topic
Posts"<cctalk at classiccmp.org>
To: cctalk at classiccmp.org
Subject: Re: data sheet for com5025
Date: Sun, 20 Aug 2006 11:57:03 -0700
On 8/20/2006 at 2:34 PM Dave McGuire wrote:
Hi Chuck
I just checked schematic I have and the MK5025 isn't the same. The part
I have is a 40 pin part, not 48 :(
Being compatable with the 2652 might be right after all. Even though used in
a 8 bit machine, the schematic shows d0-d15. I'll have to look at things
a little more.
The part is used on a floppy controller for hard sectored double density
floppies.
It is a little unusual but that is what it is used for. I've not been able
to
get firmware for it yet so I've been thinking of writing something my self.
I have some prerecoreded DD floppies to read from. I suspect it takes
advantage of the various packet features, like CRC.
Dwight
The COM5025 is mostly compatible with the 2652,
but not completely.
Both are 16-bit parts. I have info about it in a book here...My
scanner is having problems so I can't scan it, but I can type stuff up
from the book if you need it. Let me know.
Isn't the Mostek MK5025 a compatible part? IIRC, it can be used on either
an 8 or 16 bit bus.
http://www.tranzistoare.ro/datasheets/restul/502155_DS.pdf
I've also got the 7990 Lance datasheets in printed form, which is
supposedly also compatible.
Cheers,
Chuck
12:37 a.m.
New subject: data sheet for com5025
On 8/20/2006 at 9:08 PM dwight elvey wrote:
The part is used on a floppy controller for hard
sectored double density
floppies. It is a little unusual but that is what it is used for.
Not that unusual! I've used a 2651 USART on a floppy controller. Used a
9914 data separator and the USART handshaking lines for drive control.
Worked just fine. Wasn't terribly hard to program either.
IIRC, some of the USRTs will not include SYN characters in the CRC (if it
computes one for you), so you may have use a bit of software for your CRCs.
Where the USRT shines is in detecting the bit pattern (address mark) that
signifies the start of a sector.
Cheers,
Chuck
12:55 a.m.
New subject: data sheet for com5025
On 8/20/06, Chuck Guzis <cclist at sydex.com> wrote:
Isn't the Mostek MK5025 a compatible part? IIRC,
it can be used on either
an 8 or 16 bit bus.
http://www.tranzistoare.ro/datasheets/restul/502155_DS.pdf
There's a pinout and some sample code for the PDP-11 in the DPV-11
(M8020) manual...
http://bitsavers.org/pdf/dec/qbus/EK-DPV11-TM-002_Nov80.pdf
-ethan
20 Aug
20 Aug
6:25 p.m.
New subject: data sheet for com5025
On 8/21/06, dwight elvey <dkelvey at hotmail.com> wrote:
Hi
Does anyone have a pointer to a data sheet for a com5025? I believe
it to be a synchronous serial chip but I've not found much on the web.
We used the COM5025 on the Unibus versions of the COMBOARD. I have
several hundred of them new in tubes, FWIW. We used them for
byte-oriented synchronous serial protocols (HASP, 3780) and switched
to the Z8530 to support bit-stuffing protocols like SNA.
I do have data sheets on them, but not yet scanned, and in any case,
10,000 miles from here. I would think that someone on the list could
come up with an electronic copy months before I could.
I think it is compatable with a 2652 but the only
thing I can find on that
is a 16 bit part from Philips. I don't think this is a 16 bit appliction.
I don't have any information on the 2652, but in the case of the
COM5025, it's found on a couple of DEC's sync serial boards (DU11?),
that's why we used it. The COMBOARD was the descendent of the
HASPBOX, a product that was 100% DEC hardware (either an 11/04 or
11/03 with a 16-bit parallel link back to the (big) PDP-11 host and a
DEC sync serial card to the IBM box on the other end of the link.
Essentially, the COMBOARD was a single-board implementation of the
HASPBOX with a 68000 as the processor rather than a PDP-11. As such,
I _think_ the COM5025 works on either a 16-bit or an 8-bit host bus,
but we always had them on 16-bit CPUs.
-ethan
2:14 p.m.
Jules Richardson <julesrichardsonuk at yahoo.co.uk> wrote:
That is a shame - I imagine to a lot of people the aim
was the fun in
assembling a kit, rather than the cost saving...
Well, it did come with a schematic, at least!
And it's not like you could figure out its video generation by just
reading the schematic, either :-)
I think you're right and that only applies to UK
machines; other sites I've
seen suggest that the total number produced and sold worldwide was over 100,000.
It's interesting how rare they seem to be considering those sales figures - I
mean there are plenty of other machines around where sales were only a
fraction of that and yet there's still a healthy number in private hands.
Two factors:
1. The ZX80 is so compact that I'm sure there are many of them still tucked
away into corners or even between books on bookshelves.
2. The ZX80 was SO entry level that anyone really interested in computers
moved on to a better platform very very quickly.
Yeah, it was nominally expandable, and I even built a couple little
doo-dads that went onto the expansion connector, but the whole setup was
so physically unstable!
I'm going to leave out the true factor, which is how the ZX80's wedge
shape immediately inspires everyone to use it as a doorstop :-)
Tim.
..
2:33 p.m.
I have one that I built into a large case with large monitor , similar
to the PET , with several expansion boards. I have owned it since I
bought it new and it now sits and gathers dust in the garage.
On 8/20/06, Tim Shoppa <shoppa_classiccmp at trailing-edge.com> wrote:
Jules Richardson <julesrichardsonuk at
yahoo.co.uk> wrote:
--
Jim Isbell
"If you are not living on the edge, well then,
you are just taking up too much space."
That is a shame - I imagine to a lot of people
the aim was the fun in
assembling a kit, rather than the cost saving...
Well, it did come with a schematic, at least!
And it's not like you could figure out its video generation by just
reading the schematic, either :-)
I think you're right and that only applies to
UK machines; other sites I've
seen suggest that the total number produced and sold worldwide was over 100,000.
It's interesting how rare they seem to be considering those sales figures - I
mean there are plenty of other machines around where sales were only a
fraction of that and yet there's still a healthy number in private hands.
Two factors:
1. The ZX80 is so compact that I'm sure there are many of them still tucked
away into corners or even between books on bookshelves.
2. The ZX80 was SO entry level that anyone really interested in computers
moved on to a better platform very very quickly.
Yeah, it was nominally expandable, and I even built a couple little
doo-dads that went onto the expansion connector, but the whole setup was
so physically unstable!
I'm going to leave out the true factor, which is how the ZX80's wedge
shape immediately inspires everyone to use it as a doorstop :-)
Tim.
..
21 Aug
21 Aug
4:52 p.m.
On 20/8/06 19:33, "Jim Isbell, W5JAI" <jim.isbell at gmail.com> wrote:
I have one that I built into a large case with large
monitor , similar
to the PET , with several expansion boards. I have owned it since I
bought it new and it now sits and gathers dust in the garage.
That sort of enhanced ZX80 I'd love to see, are you sure you're thinking
about the ZX80 and not something bigger (even a ZX81?) The ZX80's board is
smaller than a sheet of A4 paper and wasn't that expandable......
--
Adrian/Witchy
Binary Dinosaurs creator/curator
Www.binarydinosaurs.co.uk - the UK's biggest private home computer
collection?
20 Aug
20 Aug
3:49 p.m.
Tim Shoppa wrote:
I'm going to leave out the true factor, which is
how the ZX80's wedge
shape immediately inspires everyone to use it as a doorstop :-)
Nope ... way too
light for that!
The real fun is buiding your own from scratch! No kit here --
just order the parts.
http://home.micros.users.btopenworld.com/zx80/zx80.html
6:12 p.m.
> I did a google search and looked on Wikipedia but
some of the details
> there do NOT match my memory. They say there were only 50,000 ZX80's sold
> and this seems to be a ridiculously low number for a mass-market
> machine sold through many different channels.
Does that 50K number include those that were sold as "TIMEX Sinclair"?
(USA market)
3:34 p.m.
On Sun, Aug 20, 2006 at 09:51:06AM -0400, Tim Shoppa wrote:
I did a google search and looked on Wikipedia but some
of the details
there do NOT match my memory. They say there were only 50,000 ZX80's sold
and this seems to be a ridiculously low number for a mass-market
machine sold through many different channels. They say that the Sinclair
brand was only in the UK and this does not match my experience of having
bought one in the US (or the
ads in 1980 Radio-Electronics). But this was 26 years ago, so my memory
isn't exactly sharp either!
Certainly at the time of the spectrum, Sinclair machines were sold
stateside under the "Timex" brand weren't they? Although I've never
seen
reports of a timex branded ZX80!
To this day I'm sorry that my ZX80 was thrown out with a bunch of childhood junk, sad
to admit, I've always had the impression that they were MUCH rarer than 50 000 units.
I suspect that the figure of 50 000 also includes other "commonwealth" countries
(like South Africa, where I stay) Also, I recall that my unit always had problems showing
a steady tv picture.
Cheers,
Jonathan.
5:17 p.m.
On Aug 20, 2006, at 3:34 PM, Jonathan Groll wrote:
Certainly at the time of the spectrum, Sinclair
machines were sold
stateside under the "Timex" brand weren't they? Although I've never
seen
reports of a timex branded ZX80!
I have a store-bought Timex-branded ZX81 (Timex/Sinclair 1000). My
grandmother bought it for me for my birthday when they hit US
department stores for $99.
-Dave
--
Dave McGuire
Cape Coral, FL
7:53 p.m.
At 14:51 20/08/2006, Tim Shoppa wrote:
I did a google search and looked on Wikipedia but some
of the details
there do NOT match my memory. They say there were only 50,000 ZX80's sold
and this seems to be a ridiculously low number for a mass-market
machine sold through many different channels. They say that the Sinclair
brand was only in the UK and this does not match my experience of having
bought one in the US (or the
ads in 1980 Radio-Electronics). But this was 26 years ago, so my memory
isn't exactly sharp either!
Are you sure you are thinking of the ZX80 - flat and white with a
hump at the back - and not the ZX81 (squarer, black)?
The ZX81 (and then the ZX Spectrum) was indeed mass-market, sold here
by major high street chains and definitely under the Timex brand in
the US. My only experience of seeing the ZX80 was in a few magazine
adverts as purely a mail-order kit, but with built ones
available... The ZX81 was only a year later.
I bought and built the ZX81 kit, and only later inherited the ZX80 I
still have. I really wish I'd not got rid of the '81 now - I had
several, in the end, with loads of accessories, and I swapped it all
for something so inconsequential that I can't even remember what it was, now..
Rob
21 Aug
21 Aug
4:36 a.m.
On Mon, Aug 21, 2006 at 12:53:47AM +0100, Rob O'Donnell wrote:
I bought and built the ZX81 kit, and only later
inherited the ZX80 I
still have. I really wish I'd not got rid of the '81 now - I had
several, in the end, with loads of accessories, and I swapped it all
for something so inconsequential that I can't even remember what it was,
now..
It is all quite tragic actually, we all wish we hadn't gotten rid of
them, yet those who do still own them keep 'em in the cupboard and maybe
pull them out once a year to look at... I'd be too scared to overuse the
membrane keyboard on an aged model, and for what purpose - 1k chess
anyone?
Jonathan
4:45 p.m.
On 20/8/06 14:51, "Tim Shoppa" <shoppa_classiccmp at trailing-edge.com>
wrote:
I did a google search and looked on Wikipedia but some
of the details
there do NOT match my memory. They say there were only 50,000 ZX80's sold
I have it down as 'around 70,000' though that's by no means official.
and this seems to be a ridiculously low number for a
mass-market
machine sold through many different channels. They say that the Sinclair
brand was only in the UK and this does not match my experience of having
bought one in the US (or the
All machines were mail order weren't they? Yes there were adverts in a lot
of magazines of the day, but all returned to Sinclair. There was a brief
flirtation with the US and even a clone called the MicroAce.
Aha! Google is my friend:
http://www.chaotic.fsnet.co.uk/zx80/
That's not where I got my numbers from, but the author must read the same
sources I did :)
--
Adrian/Witchy
Binary Dinosaurs creator/curator
Www.binarydinosaurs.co.uk - the UK's biggest private home computer
collection?
20 Aug
20 Aug
11:25 a.m.
Out of interest, anyone know how many ZX80s were sold
as
kits? This one's a factory-built one, complete with original
ZX80 PSU. The heatsink for the regulator gets pretty hot, and
that's even without the RAM pack plugged in...
Me and a couple of friends were given kits as a prize at school, I don't
remember that much about the ZX80, apart from the regulator kept cutting out
and eventually went pop. My Father spent a couple of evenings making up a
decent stabilised PSU for it. With the PSU the ZX80 ran a lot cooler. I
never bothered with any more Sinclair products after that, once into Acorn,
I was hooked... Mind you I had the same hassle with my Acorn Atom kit too,
many owners of expanded Acorn Atom systems will tell you of the roasting
regulator on their boards.
Dave ;)
6:48 p.m.
Out of interest, anyone know how many ZX80s were
sold as
kits? This one's a factory-built one, complete with original
ZX80 PSU. The heatsink for the regulator gets pretty hot, and
that's even without the RAM pack plugged in...
Me and a couple of friends were given kits as a prize at school, I don't
remember that much about the ZX80, apart from the regulator kept cutting out
and eventually went pop. My Father spent a couple of evenings making up a decent stabilised PSU for it. With the PSU the ZX80
ran a lot cooler. I
never bothered with any more Sinclair products after that, once into Acorn,
I bought an MK14 back when it was current. That put me off Sinclair for
life...
I was hooked... Mind you I had the same hassle with my
Acorn Atom kit too,
many owners of expanded Acorn Atom systems will tell you of the roasting
regulator on their boards.
I seem to remmember you were supposed to fit a zecond regulator (7805)
and cut a link if you expaneded the Atom. Then each regulator powered
about half of the machine.
-tony
21 Aug
21 Aug
3:29 p.m.
Tony Duell wrote:
The construction guide says: "both regulators and a heatsink should be fitted
to all Atoms". I've never seen one with only a single regulator, but doubtless
a few individuals building from kits tried it. The manual gives the minimal
system with 2KB of memory as around 750mA draw, so that's within the
capabilities of some 7805 variants and not others...
More common is that the regulators have been bypassed or removed entirely and
an external supply is used. It's rare-ish to find an Atom with regulators and
heatsink still intact (maybe 25% are like this). Rarer still is to find an
Atom using an external supply where someone's actually done as the manual says
and indicated on the back that the machine's wired for 5V regulated input
rather than 8V unregulated - I expect there are a lot of toasted Atoms still
floating around!
cheers
J.
I bought an MK14 back when it was current. That put me
off Sinclair for
life...
Out of interest, what was so bad about them that wasn't typical of that class
of machine around that time? Admittedly without having been involved at the
time, it seems with hindsight that there were an awful lot of similar machines
around that sort of era with odd design quirks, very limited power,
poor-quality PCBs etc.
I was
hooked... Mind you I had the same hassle with my Acorn Atom kit too,
many owners of expanded Acorn Atom systems will tell you of the roasting
regulator on their boards.
I seem to remmember you were supposed to fit a zecond regulator (7805)
and cut a link if you expaneded the Atom. Then each regulator powered
about half of the machine. 
3:25 p.m.
Hi,
Jules Richardson said:
Tony Duell wrote:
I
never had any problems with my Mk14 (which I've still got and it still
works), an issue 2 board. The keypad was trouble right from the start and
was immediately replaced with a modified telephone one, and it's worked fine
ever since. The cassete interface, however, was a different matter, it would
shed print if you just looked at it funny with a soldering iron.
Like all Sinclair gear, designed down to a price - and then some!
I'm afraid I seem to have lost my homebrew inout relay board and sound
interface, but I think I've got the schematic somewhere...
I also have a ZX81, but the only Sinclair bit left is the main board/
processor etc. Even the ROM has been changed, and it's in a large
metal box with a 16K rampack, 2 inout boards and an 8 channel A2d card.
Ah, the good old days...
--
Cheers,
Stan Barr stanb at dial.pipex.com
The future was never like this!
I bought an MK14 back when it was current. That
put me off Sinclair for
life...
Out of interest, what was so bad about them that wasn't typical of that class
of machine around that time? Admittedly without having been involved at the
time, it seems with hindsight that there were an awful lot of similar machines
5:53 p.m.
On 21/8/06 20:25, "Stan Barr" <stanb at dial.pipex.com> wrote:
ever since. The cassete interface, however, was a
different matter, it would
shed print if you just looked at it funny with a soldering iron.
Like all Sinclair gear, designed down to a price - and then some!
The cassette interface was designed by Nick "Atom" Toop because Science of
Cambridge hadn't come up with one; he might've had to rationalise the design
to reduce costs a tad but it's all his own work.
--
Adrian/Witchy
Binary Dinosaurs creator/curator
Www.binarydinosaurs.co.uk - the UK's biggest private home computer
collection?
22 Aug
22 Aug
3:56 a.m.
Hi,
Adrian Graham said:
On 21/8/06 20:25, "Stan Barr" <stanb at
dial.pipex.com> wrote:
I didn't know that. The design's fine, it's just the quality of the board,
but small production runs and low costs presumably didn't allow for a high
quality board - unless I just got a bad one!
--
Cheers,
Stan Barr stanb at dial.pipex.com
The future was never like this!
ever since. The cassete interface, however, was
a different matter, it would
shed print if you just looked at it funny with a soldering iron.
Like all Sinclair gear, designed down to a price - and then some!
The cassette interface was designed by Nick "Atom" Toop because Science of
Cambridge hadn't come up with one; he might've had to rationalise the design
to reduce costs a tad but it's all his own work.
3:14 p.m.
On 22/8/06 08:56, "Stan Barr" <stanb at dial.pipex.com> wrote:
Nah, all the interfaces I've seen have had no writing on them :)
--
Adrian/Witchy
Binary Dinosaurs creator/curator
Www.binarydinosaurs.co.uk - the UK's biggest private home computer
collection?
The cassette interface was designed by Nick "Atom" Toop because Science of
Cambridge hadn't come up with one; he might've had to rationalise the design
to reduce costs a tad but it's all his own work.
I didn't know that. The design's fine, it's just the quality of the board,
but small production runs and low costs presumably didn't allow for a high
quality board - unless I just got a bad one!
21 Aug
21 Aug
5:51 p.m.
On 21/8/06 20:29, "Jules Richardson" <julesrichardsonuk at yahoo.co.uk>
wrote:
Tony Duell wrote:
The MK14 wasn't *really* a Sinclair product anyway, it was only sold under
the Science of Cambridge banner and wasn't touched by Uncle Clive's fingers.
Wasn't it also a clone of the Nat Semi SC/MP demo board aka SCAMP?
I bought an MK14 back when it was current. That
put me off Sinclair for
life...
Out of interest, what was so bad about them that wasn't typical of that class
of machine around that time? Admittedly without having been involved at the
time, it seems with hindsight that there were an awful lot of similar machines
around that sort of era with odd design quirks, very limited power,
poor-quality PCBs etc. More common is that the regulators have been bypassed
or removed entirely and
an external supply is used. It's rare-ish to find an Atom with regulators and
heatsink still intact (maybe 25% are like this). Rarer still is to find an
*waves* :) Mind, the one I'm thinking of has a Bloody Great Big Switch
underneath the keyboard that switches out the regulators. If I hadn't been
blessed with a few hours with Nick Toop himself while he looked over that
machine and sorted it out I'd have toasted it.....
I must post a picture of the PSU that came with that Atom, it's nearly as
wide/deep as the machine itself and twice as thick.
--
Adrian/Witchy
Binary Dinosaurs creator/curator
Www.binarydinosaurs.co.uk - the UK's biggest private home computer
collection?
6:15 p.m.
Tony Duell wrote:
Well, the keypad was terrible (I ended up soldering 20 switches from
Maplin onto the MK14 PCB, the holes and traces were there for them...).
There were some very marginal bits of logic design (hint : a '157 is a
multiplexer, a '175 is a latch, but the MK14 uses the former as a the
display output register. It works for _some_ makes of '157...). The CPU
buses are not broungt off-board, so expansion was a pain. And so on. I
wish I'd saved a little more money and bought an Acorn System 1.
I bought an MK14 back when it was current. That
put me off Sinclair for
life...
Out of interest, what was so bad about them that wasn't typical of that class
of machine around that time? Admittedly without having been involved at the time, it seems with hindsight that there were an awful
lot of similar machines
around that sort of era with odd design quirks, very limited power,
poor-quality PCBs etc.
Having collected a number of machines from that sort of period, I can
safely say that Sinclair were _by far_ the worst. And don't get me
started on his pocket calculators. I think I can get more accurate
results from a good slide rule.
More common is that the regulators have been bypassed
or removed entirely and
an external supply is used. It's rare-ish to find an Atom with regulators and
heatsink still intact (maybe 25% are like this). Rarer still is to find an
Atom using an external supply where someone's actually done as the manual says
and indicated on the back that the machine's wired for 5V regulated input
rather than 8V unregulated - I expect there are a lot of toasted Atoms still
floating around!
Releated to this was a horrible bit of Torch design. As you may know,
Torch sold an upgrade for the BBC micro which added an internal PCB
containing a Z80 running CP/N (no, that's not one of my typos...). The
Beeb power supply couldn't really supply that as well, so what you did
was remove the Beeb PSU altogether, connected a cable to the power
connections on the Beeb's mainboard, and run the whole thing off a PSU
in the (Torch-supplied) disk drive unit.
The problem was that the cable supplied was essentially mains cabled,
terminated in a Bulgin connector that was sometimes (albeit rarely) used
for mains. And of course some people, finding a machine after <n> years
and not realising the PSU had been removed, promptly connected this cable
to the mains. Appliing 240V AC to the 5V line does not improve matters...
-tony
6:37 p.m.
On 8/21/2006 at 11:15 PM ard at p850ug1.demon.co.uk wrote:
Having collected a number of machines from that sort of
period, I can
safely say that Sinclair were _by far_ the worst. And don't get me
started on his pocket calculators. I think I can get more accurate
results from a good slide rule.
My first product from Sir Clive was his LED watch kit. I received a case,
strap and lens, but no PCB or electronic parts. When I wrote them to point
out the problem, I was sent a PCB from some other product.
I wonder to this day if the kit was for a real, working watch.
Cheers,
Chuck
22 Aug
22 Aug
3:17 a.m.
On 21/8/06 23:37, "Chuck Guzis" <cclist at sydex.com> wrote:
My first product from Sir Clive was his LED watch kit.
I received a case,
strap and lens, but no PCB or electronic parts. When I wrote them to point
out the problem, I was sent a PCB from some other product.
Ah yes, the famous exploding Black Watch, still going for silly money on
epay even if it doesn't work!
--
Adrian/Witchy
Binary Dinosaurs creator/curator
Www.binarydinosaurs.co.uk - the UK's biggest private home computer
collection?
1:31 p.m.
On 8/22/2006 at 8:17 AM Adrian Graham wrote:
Ah yes, the famous exploding Black Watch, still going
for silly money on
epay even if it doesn't work!
After I couldn't get any cooperation in getting the needed parts for mine,
I tossed it out. Your comment probably explains why the company
stonewalled on my requests for a complete kit. I bought a Commodore watch
instead--for $15. Sadly, I don't have it any longer, but I still do have
my National Semiconductor LCD watch. In both instances, perspiration did a
number on the circuitry.
Cheers,
Chuck
1:40 p.m.
On 22/8/06 18:31, "Chuck Guzis" <cclist at sydex.com> wrote:
On 8/22/2006 at 8:17 AM Adrian Graham wrote:
Heh, I'm wearing my Commodore watch now, datestamped 07/77 and still getting
admiring glances from all and sundry. When I flew from the UK to Guernsey
(in the Channel Islands) the other weekend I wasn't allowed to take it into
the cabin because of the terrorist threats - "it looks like it might set
something off!" was one comment. Nice :)
--
Adrian/Witchy
Binary Dinosaurs creator/curator
Www.binarydinosaurs.co.uk - the UK's biggest private home computer
collection?
Ah yes, the famous exploding Black Watch, still
going for silly money on
epay even if it doesn't work!
After I couldn't get any cooperation in getting the needed parts for mine,
I tossed it out. Your comment probably explains why the company
stonewalled on my requests for a complete kit. I bought a Commodore watch
instead--for $15. Sadly, I don't have it any longer, but I still do have
my National Semiconductor LCD watch. In both instances, perspiration did a
number on the circuitry. 
21 Aug
21 Aug
6:59 p.m.
On Monday 21 August 2006 06:15 pm, Tony Duell wrote:
Torch sold an upgrade for the BBC micro which added an
internal PCB
containing a Z80 running CP/N (no, that's not one of my typos...).
What is that, then?
--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space, a critter that can
be killed but can't be tamed. --Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James
M Dakin
22 Aug
22 Aug
3:43 a.m.
Roy J. Tellason wrote:
On Monday 21 August 2006 06:15 pm, Tony Duell wrote:
It was Torch's own CP/M variant - I don't think it was really any less
compatible than lots of other CP/M variants, but the main difference was that
it added networking support for TorchNET in systems that were based around the
BBC micro (and hence had Econet ability - TorchNET was just a different layer
over the standard Econet lower levels)
Torch sold an upgrade for the BBC micro which
added an internal PCB
containing a Z80 running CP/N (no, that's not one of my typos...).
What is that, then?
5:53 p.m.
On Monday 21 August 2006 06:15 pm, Tony Duell wrote:
CP/N was Torch's CP/M-a-like. It could run most (all?) CP/M software IIRC.
-tony
Torch sold an upgrade for the BBC micro which
added an internal PCB
containing a Z80 running CP/N (no, that's not one of my typos...).
What is that, then?
3:30 a.m.
Tony Duell wrote:
Hmm, that is really surprising about the (lack of) expansion ability - I would
have thought it's one of the primary reasons in choosing a machine of that
class. I can't imagine doing something like in the ZX series (solder-pad edge
connector) would exactly have put the manufacturing cost up by much!
Tony Duell
wrote:
Well, the keypad was terrible (I ended up soldering 20 switches from
Maplin onto the MK14 PCB, the holes and traces were there for them...).
There were some very marginal bits of logic design (hint : a '157 is a
multiplexer, a '175 is a latch, but the MK14 uses the former as a the
display output register. It works for _some_ makes of '157...). The CPU
buses are not broungt off-board, so expansion was a pain. I bought an MK14 back when it was current. That
put me off Sinclair for
life...
Out of interest, what was so bad about them that wasn't typical of
that class
of machine around that time? Admittedly without having been involved at the And so on. I
wish I'd saved a little more money and bought an Acorn System 1.
True - at least there was the ability there to re-use the CPU card and add a
eurocard lack later along with all the later System cards. Mind you, from
memory of Acorn ads they didn't really play up any future expansion ability -
I don't think Acorn saw it as a real selling point back then.
Releated to this was a horrible bit of Torch design.
As you may know,
Torch sold an upgrade for the BBC micro which added an internal PCB
containing a Z80 running CP/N (no, that's not one of my typos...). The
Beeb power supply couldn't really supply that as well, so what you did
was remove the Beeb PSU altogether, connected a cable to the power
connections on the Beeb's mainboard, and run the whole thing off a PSU
in the (Torch-supplied) disk drive unit.
You know, my prototype Torch Z80 disk unit has power out at the back; I can't
remember whether the production ones were like that or not. It had never
occurred to me that someone would want to power the machine from it!
In a way I'm surprised that the beeb PSU couldn't cope though - the current
draw can't be a lot worse than other various internal add-ons for the beeb.
I've certainly seen a lot of beebs running the Torch copro without any PSU mods.
cheers
J.
--
A. Because it destroys the natural flow of conversation.
Q. What's wrong with top posting ?
3:31 a.m.
On 22/8/06 08:30, "Jules Richardson" <julesrichardsonuk at yahoo.co.uk>
wrote:
According to this advert from 1977ish some of the CPU signals go directly to
the edge connector at the back, also note the expansion at the lower right
for an external keyboard..
http://www.binarydinosaurs.co.uk/scripts/picshow.php?image=mk14.jpg&fol…
Museum/Adverts&back=/Museum/Adverts/index.php
(erk, url wrappage!)
Also, here's a later one that features such niceties as a 'vdu module' which
to me looks like a eurocard.....
Also, here's Nick Toop's own MK14 in large JPG format; note later membrane
keyboard, power module and wires at the top going to the cassette interface.
The metal box it's in was Nick's own design but Clive never took it on,
probably because of cost :)
http://www.binarydinosaurs.co.uk/nickmk14.jpg
--
Adrian/Witchy
Binary Dinosaurs creator/curator
Www.binarydinosaurs.co.uk - the UK's biggest private home computer
collection?
Well, the
keypad was terrible (I ended up soldering 20 switches from
Maplin onto the MK14 PCB, the holes and traces were there for them...).
There were some very marginal bits of logic design (hint : a '157 is a
multiplexer, a '175 is a latch, but the MK14 uses the former as a the
display output register. It works for _some_ makes of '157...). The CPU
buses are not broungt off-board, so expansion was a pain.
Hmm, that is really surprising about the (lack of) expansion ability - I would
have thought it's one of the primary reasons in choosing a machine of that
class. I can't imagine doing something like in the ZX series (solder-pad edge
connector) would exactly have put the manufacturing cost up by much! 
6:11 p.m.
Hmm, that is really surprising about the (lack of) expansion ability - I would
have thought it's one of the primary reasons in choosing a machine of that
class. I can't imagine doing something like in the ZX series (solder-pad edge
connector) would exactly have put the manufacturing cost up by much!
According to this advert from 1977ish some of the CPU signals go directly to
the edge connector at the back, also note the expansion at the lower right
for an external keyboard..
6:51 p.m.
On 22/8/06 23:11, "Tony Duell" <ard at p850ug1.demon.co.uk> wrote:
Ah, the useful stuff, then :o|
--
Adrian/Witchy
Binary Dinosaurs creator/curator
Www.binarydinosaurs.co.uk - the UK's biggest private home computer
collection?
According to
this advert from 1977ish some of the CPU signals go directly to
the edge connector at the back, also note the expansion at the lower right
for an external keyboard..
Typical Sinclair misleading advert, then...
The SC/MP has some I/O lines on the chip. IIRC there are 3 flag outputs
(on/off signals controlled by bits in the CPU status register), 2 sense
inputs (which can be read as bits in the CPU status register, one can
also be used as an interrupt line), and serial I/O lines which go to the
'ends' of the CPU extenstion register (which can be shifted under program
control). These lines _are_ brought out to the connector at the back.
But the CPU buses aren't.
23 Aug
23 Aug
7:08 p.m.
The SC/MP has
some I/O lines on the chip. IIRC there are 3 flag outputs
(on/off signals controlled by bits in the CPU status register), 2 sense
inputs (which can be read as bits in the CPU status register, one can
also be used as an interrupt line), and serial I/O lines which go to the
'ends' of the CPU extenstion register (which can be shifted under program
control). These lines _are_ brought out to the connector at the back.
But the CPU buses aren't.
Ah, the useful stuff, then :o|
24 Aug
24 Aug
4 a.m.
Hi,
Tony Duell said:
Actually, those CPU I/O lines _are_ useful. Remember on the MK14 that the
8154 chip was _optional_. Without it, that's all the I/O you get.
IIRC that cassette interface (which I never got to work properly...) used
one of the flag lines as the output (record) and one of the sense lines
together with the serial input line (strapped together) as the input
(playback).
Yep, flag zero for record and sense B and SIN for play. (I still have
the manuals and diagrams on my desk here from when I was looking stuff
up the other day.)
My cassete interface works fine, I loaded a program with it when I
was digging the manual out, but it's a bit fussy as to level.
--
Cheers,
Stan Barr stanb at dial.pipex.com
The future was never like this!
The SC/MP has some I/O lines on the chip. IIRC there
are 3 flag outputs
(on/off signals controlled by bits in the CPU status register), 2 sense
inputs (which can be read as bits in the CPU status register, one can
also be used as an interrupt line), and serial I/O lines which go to the
'ends' of the CPU extenstion register (which can be shifted under program
control). These lines _are_ brought out to the connector at the back.
But the CPU buses aren't.
Ah, the useful stuff, then :o|
22 Aug
22 Aug
8:32 a.m.
At 08:30 22/08/2006, Jules Richardson wrote:
You know, my prototype Torch Z80 disk unit has power
out at the
back; I can't remember whether the production ones were like that or
not. It had never occurred to me that someone would want to power
the machine from it!
There's one on eBay at the moment - Item 280020173050 - with a
picture clearly showing the rear with a DC out connector. It appears
to only be +/- 5V from the labeling, which I would have thought
insufficient to run a Beeb. So what WAS it used for??
Rob.
11:19 a.m.
You know, my
prototype Torch Z80 disk unit has power out at
the back; I
can't remember whether the production ones
were like that or not. It
had never occurred to me that someone would want to power
the machine
from it!
There's one on eBay at the moment - Item 280020173050 - with
a picture clearly showing the rear with a DC out connector.
It appears to only be +/- 5V from the labeling, which I would
have thought insufficient to run a Beeb. So what WAS it used for??
1:57 p.m.
Rob O'Donnell wrote:
At 08:30 22/08/2006, Jules Richardson wrote:
Heh, I know the seller - he's tried to interest me in that one a few times :-)
My prototype one is the same design, but uses the (far more attractive)
two-tone grey paint that Torch used for most of their systems, rather than the
"poop brown". For some reason they changed it for the production units...
You know, my prototype Torch Z80 disk unit has
power out at the back;
I can't remember whether the production ones were like that or not. It
had never occurred to me that someone would want to power the machine
from it!
There's one on eBay at the moment - Item 280020173050 - with a picture
clearly showing the rear with a DC out connector. It appears to only be
+/- 5V from the labeling, which I would have thought insufficient to run
a Beeb.
Ahh, no - beebs use RS423 for serial, so only need +/- 5V internally on the
system board. They do have +12V on the aux power connector on the beeb's PSU
itself, but that's not used internally by the system.
I'm still surprised that there were any beebs incapable of running the Torch
board from their own PSU though. I believe there was a change to PSU spec at
some point early in the beeb's life though, so maybe very early systems
couldn't cope.
cheers
J.
6:23 p.m.
I'm still surprised that there were any beebs
incapable of running the Torch
board from their own PSU though. I believe there was a change to PSU spec at
some point early in the beeb's life though, so maybe very early systems
couldn't cope.
Very early Beebs have a linear supply (a torroidal transformer and a
number of 7805 regualtors IIRC). On early Beeb boards, the 3 5V pins are
separate, and each is supplied by a different 7805. Later boards,
designed for use with the SMPSU, have the 5V pins connected together.
This linear PSU was well-known for burning the varnish off the dining room
table....
-tony
6:17 p.m.
There's one on eBay at the moment - Item 280020173050 - with a
picture clearly showing the rear with a DC out connector. It appears
to only be +/- 5V from the labeling, which I would have thought
insufficient to run a Beeb. So what WAS it used for??
That's all a Beeb needs. +5V for the logic and the +ve supply to the
RS423 buffers, -5V for some of the analogue stuff and the -ve supply to
the RS423 buffers. The normal PSU just gives out those 2 voltages.
A Beeb will actually boot with just the +5V line connected, but you'll
have no sound, and the serial port doesn't work. I found this out in the
obvious way when restoring my Acorn Cambridge Workstation (which has a
Beeb B+ in the bottom, of course)
-tony
1:49 p.m.
Hi,
Jules Richardson said:
RE: Mk 14
Hmm, that is really surprising about the (lack of)
expansion ability -
I would
have thought it's one of the primary reasons in choosing a machine of that
class. I can't imagine doing something like in the ZX series (solder-pad edge
connector) would exactly have put the manufacturing cost up by much!
Indeed, the lack of expandability was a real downer. I wanted to add a
couple of k ram but it would have required major surgery. By that time,
however, I had another SC/MP board by a local firm (Kemitron, I think)
so the MK14 survives in un-butchered form. The optional in/out chip lines
(an INS8154) were brought out to an (0.15-inch pitch) edge connector
together with the processor flag and sense lines, and the serial in/out.
The keybourd had its own connector.
To find that info I had to dig out the manual and I couldn't resist
connecting the Mk14 to the shack power supply, it still works :-)
--
Cheers,
Stan Barr stanb at dial.pipex.com
The future was never like this!
6:08 p.m.
Well, the keypad was terrible (I ended up soldering 20 switches from
Maplin onto the MK14 PCB, the holes and traces were there for them...).
There were some very marginal bits of logic design (hint : a '157 is a
multiplexer, a '175 is a latch, but the MK14 uses the former as a the
display output register. It works for _some_ makes of '157...). The CPU
buses are not broungt off-board, so expansion was a pain.
Hmm, that is really surprising about the (lack of) expansion ability - I would
have thought it's one of the primary reasons in choosing a machine of that
class. I can't imagine doing something like in the ZX series (solder-pad edge
connector) would exactly have put the manufacturing cost up by much! And so on. I
wish I'd saved a little more money and bought an Acorn System 1.
True - at least there was the ability there to re-use the CPU card and add a
eurocard lack later along with all the later System cards. Mind you, from
memory of Acorn ads they didn't really play up any future expansion ability -
I don't think Acorn saw it as a real selling point back then. Releated to this was a horrible bit of Torch
design. As you may know,
Torch sold an upgrade for the BBC micro which added an internal PCB
containing a Z80 running CP/N (no, that's not one of my typos...). The
Beeb power supply couldn't really supply that as well, so what you did
was remove the Beeb PSU altogether, connected a cable to the power
connections on the Beeb's mainboard, and run the whole thing off a PSU
in the (Torch-supplied) disk drive unit.
You know, my prototype Torch Z80 disk unit has power out at the back; I can't
remember whether the production ones were like that or not. It had never
occurred to me that someone would want to power the machine from it!
In a way I'm surprised that the beeb PSU couldn't cope though - the current
draw can't be a lot worse than other various internal add-ons for the beeb.
I've certainly seen a lot of beebs running the Torch copro without any PSU mods.
YEs, but that wasn't 'offiical' either. IIRC Acorn specifically fobade
you to run anything off the Beeb's PSU. I think Torch tried to do things
properly.
-tony
2:50 p.m.
Tony Duell wrote:
There were some very marginal bits of logic design
(hint : a '157 is a
multiplexer, a '175 is a latch, but the MK14 uses the former as a the
display output register. It works for _some_ makes of '157...).
I read somewhere that the MK14 was redesigned by National Semiconductor
so that it used chips made by them, exclusively. This was done for
free, or at least in return for buying lots of Nat Semi chips to
actually build the machines. Maybe the Nat Semi '157s work, and
others don't?
--
John Honniball
coredump at gifford.co.uk
21 Aug
21 Aug
7:57 a.m.
I don't
remember that much about the ZX80, apart from the regulator kept cutting
out
and eventually went pop. My Father spent a couple of evenings making up a
decent stabilised PSU for it.
Yet again classiccmp triggers a Proustian moment of nostalgia for me :) This
time it's
that if you so much as looked at the 16K RAM pack funny the connection was
so crappy there would be a huge flicker on the TV screen and everything
would be... gone.
Happy days.
--
Pete Edwards
"Prediction is very difficult, especially if it's about the future" - Niels
Bohr
9:55 a.m.
From: "Pete Edwards" <stimpy.u.idiot at
gmail.com>
Hi
I put some DC#4 silicon grease on the connector pins and one could
bounce the unit on the table without causing it to drop connections.
Most of the problem was caused by dissimilar materials. The boards
were just solderplate pins.
Dwight
I don't
remember that much about the ZX80, apart from the regulator kept cutting
out
and eventually went pop. My Father spent a couple of evenings making up a
decent stabilised PSU for it.
Yet again classiccmp triggers a Proustian moment of nostalgia for me :)
This
time it's
that if you so much as looked at the 16K RAM pack funny the connection was
so crappy there would be a huge flicker on the TV screen and everything
would be... gone.
Happy days.
1:33 p.m.
From: "Pete Edwards" <stimpy.u.idiot at gmail.com>
Yet again classiccmp triggers a Proustian moment of
nostalgia for me :)
This
time it's
that if you so much as looked at the 16K RAM pack funny the connection was
so crappy there would be a huge flicker on the TV screen and everything
would be... gone.
Blutak, lots and lots of Blutak............
Jim.
4:38 p.m.
On 20/8/06 13:30, "Jules Richardson" <julesrichardsonuk at yahoo.co.uk>
wrote:
I've got a ZX80 here (issue 2A) which has a keyboard overlay attached that
looks very like that of a Sinclair ZX81.
That's because it is :)
The ROM in the machine is dated week 16 of 1981, and
carries the marking
C77018, and a 1981 copyright.
Is this a machine that's been subjected to a ZX81 upgrade kit or something? I
wasn't aware that such a thing existed.
Yep, the 'enhanced' ZX80 ROM was released before the ZX81 hit, as well as
allowing frustrated ZX80 owners to upgrade their machines afterwards too. I
*think* that's the right way round, I can remember ads for the ZX81 that
also featured ROM upgrades for the '80.....
ZX80 legend underneath. However, two black
press-fittings attach it to the PCB
at the corners of the front edge - are these press fittings there on all
ZX80s, or have these been added in order to secure the overlay in place?
They're on all ZX80s:
http://www.binarydinosaurs.co.uk/Museum/Sinclair/zx80/
The machine came with a "ZX 16K RAM" module
(red lettering) which I assume is
later and more in keeping with a ZX81? Separately though I do have a module
marked as "ZX80 16K Byte RAM Pack" (white lettering). Question is, are they
interchangeable and the lettering was altered - or does the ZX80 variant map
They're interchangeable, indeed I use a ZX81 RAM pack with my ZX80 and it's
fine. The white lettered RAM pack is rarer than the red lettered one from
what I remember.
I've also got a ROM marked as: "ROM contents
copyright 1980 Sinclair Research
Ltd" - is this the original ZX80 ROM (and the ROM in the machine is an
upgrade), or is this likely something else entirely?
It's the original ROM - the upgrade was fully removable for some reason,
simply undo the ZX81 overlay and put the old ROM back in. I can't imagine
why anyone would want to do that, but I'm pleased that you can!
Curiously there are a few stray fibres glued to the
underside of the PCB -
presumably these are a left-over of cheap PCB manufacture and Sinclair's
horrible quality control! :-)
Did they ever have any?
--
Adrian/Witchy
Binary Dinosaurs creator/curator
Www.binarydinosaurs.co.uk - the UK's biggest private home computer
collection?
6580
days inactive
6587
days old
62 comments
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