Naked at 30: Osborne 1 stripped to its chips The Osborne 1 – the first mass-market portable computer – turns 30 years old this month. And what better way to celebrate than by tearing one apart? One problem: I couldn't get my hands on an original Osborne 1. But I was able to tear into the next best thing: the slightly remodeled follow-on to the original, also known as the …
Owned the Rev A myself. And did have the external monitor as well as the 300 baud Osborne pulse dialing modem that fit into the floppy holder slot by the port. The Rev A had double density single sided drives where the original had single density. So everyone cut the notch in their floppies so we could turn them over and use the backside. My Osborne I ran: Turbo Pascal, COBOL, LISP, C, Z80 Macro Assembler in addition to the normal package and the plethora of add ons through the many BBS CP/M sites. At school, armed with a 300 baud modem, I did my mainframe work via Wordstar and uploaded it to save valuable "dollar" allotments on the school's mainframe. I was the envy of my dorm since 128 scrollable display is good enough to display the majority of mainframe output which was formatted for a maximum 132 character line printer. I made my own modifications to OSWYLBUR to handle the strange Osborne I modem... and many of us replace the CP/M shell with ZCPR, a command replacement with more features. I even hacked in a pulse dialing modem routine in place of the built in DIR command, since most people used a directory listing program from disk instead. I also programmed a game using the Software Toolworks C compiler where you flew around the screen and turned asterisks into boxes. The asterisks would kill you if you ran into them and the boxes were like walls, so as you played your ability to move about the screen decreased. What fun! I also wrote a mainframe 370 assembler in macro Z80 assembler. This allowed me to do a lot of my labs without using valuable compute time... just had to upload the final product. In high school, I developed a text adventure game (ala Infocom) where you had to solve chemistry problems to get through obstacles. In my junior year of college I wrote a small BBS in assembler for my Technical Writing class.
Great machine... I wish I had never given it away. It was very useful. It was fun keeping my dorm mates up all night as they listen to my TTX 1014 daisy wheel printer typing away....
In order to get the screen to light up at all, the horizontal section needs to be working to generate the kilovolt(s) needed to attract the electron beam from the cathode to the front of the tube to hit the phosphor, so it could be that the horizontal oscillator and the driver transisitor and flyback and damper are all working, but the horizontal deflection coil(s) is(are) open or one end has come disconnected due to a bad solder joint.
Unless for some reason they did everything backwards and the vertical deflection section is the one that generates the high voltage for the CRT, in which case you just rotate the whole thing 90 degrees and troubleshoot like an ordinary loss of vertical deflection.
I've used half those chips in my own designs, back in the day... yes, the M8877 is a Fujitsu floppy controller.
If you feel the urge to fiddle, replace the line driver transistor in the monitor - it'll probably be a TO3 package, maybe on a heat sink, close to the line output transformer. There's a good chance it will all then work; old TTL electronics are a lot tougher than you think.
The MM5290 datasheet can be found here: http://www.alldatasheet.com/datasheet-pdf/pdf/148600/NSC/MM5290.html
Brings back fond memories of doing so many assembler runs on my IBM PC's floppies that the disks wore out! After a while, we only bought Verbatims, since they lasted the longest.
It took two floppies to be useful, especially with single density drives. One had the program & its overlays, the other your data disk.
As it was there was software that wouldn't fit because it expected the greater capacity of the IBM-format 8" disks. When double-density became common, it helped, but it wasn't until quad density came along (not to be confused with high density 1.2MB diskettes) that mini-floppies had the same space available.
Never played much with CP/M, but I remember the bad old days of only having one floppy in DOS:
Insert disc in Drive A: to continue...
Insert disc in Drive B: to continue...
Insert disc in Drive A: to continue...
Insert disc in Drive B: to continue...
Insert disc in Drive A: to continue...
Insert disc in Drive B: to continue...
Insert disc in Drive A: to continue...
Insert disc in Drive B: to continue...
Ah, memories
It's the 74LS** chip numbers you should be looking at.
The K8241 = 74LS00 contains four 2-input NAND gates.
The K8243 = 74LS04 contains six inverters (NOT gates).
These are 5V TTL (transister transistor logic) lower-power Schottky chips. I used to play with them as a kid. Happy days, when some chips contained < 100 transistors!
back in the days when I did some field service work, 9 out of 10 times this horizontal deflection issue (vertical line in the middle) was just a solder joint gone bad. 5 minutes work to fix...
Inspect the solder points of the video board and look for fine circular cracks or lines on the solder.
Absolutely right about the solder joint; but from my very limited experience of iffy CRTs, the next things to check are resistors and capacitors - all cheap, thank goodness! - before you need to start worrying about anything complex or difficult.
Just make damn sure the caps are empty before you start work.
I have seen someone go flying when they accidentally toutched the wrong side of a flyback transformer. Well named that.
Landed on his arm and broke it.
There isnt much actual power in there, but there is enough voltage to cause a small current flow, and it doent take much of a current flow near a nerve to cause the attached muscles to contract violently
Yup. Yup. Many moons ago I found a rather large color TV at a garage sale. I was told it worked, kind of, and I traded $5 of my hard-earned paper route money for it. Walked it home on my bike and immediate set to work on it.
I saw several cold solder joints and began screw driver surgery to reach them. The long-shank driver brushed across the terminals of the transformer or one of its compatriot capacitors -- it is all a bit fuzzy at that point -- and my arm shot right up into the air, my hand releasing the screw driver which became embedded about a half-inch into my bedroom ceiling.
Lesson well learned that day.
Paris, heed the stickers.
2002, 1084, etc... these are all TLL-capable. Just need to work the pin-out. Matter of fact, a PCjr monitor will probably work as well; I made an adapter to connect my Commodore 128's TTL output to a PCjr monitor. Found it in storage recently...
Paris, ah, yes, memories, indeed...
I got one this last year that I'm using, along with an Ampro, Big Board, and Kaypro IV. The Ampro and Osborne are my favorites.
I mostly write code in assembly and Turbo Pascal.
I also use mine as a luggable. For a week I take it into the computer classes I teach to demonstrate some visible computer hardware for my students. It's not an Eee PC 900 by any means (my usual portable), but it does travel very well in spite of its weight. The students _love_ floppy drives (and Zork).
Good writeup!
Your mystery chips have the date code on top, designation on the bottom. You've got National Semi MM5290N-2 memory chips produced in the 29th week of 1982. Be sure to list them as *****RARE***** on ebay. ;)
One of my first jobs, in the early eighties, was programming something which was probably one of these (it was a CPM machine in a very similar case, with the detachable keyboard).
I don't have the remotest recollection what the project was ... completely erased from my memory :( Scary.
@James Holt - two floppies because it didn't have a hard drive (I think). Compiler disk in A:, source code disk in B:
Osbourne 1 was the first computer I seriously 'networked' using RS232 and lovely CP/M whilst at university ... there was an os that people understood and it did what it was told! Imagine routinely hacking os code nowadays (using info from something they called 'the manual') without breaking at least three layers of MS system rubbish ... I still remember the geeky amusement of the Spitting Image 'RS232 interface lead' song as we kermitted stuff about :-) Two drives were amazingly helpful otherwise disk swapping with a pile of half a dozen floppies became a nightmare.
We had a Kaypro ll as a Wordstar engine for a while ... worked fine but somehow never had quite the same impact as the Osbourne ... perhaps some of the teenage geekiness had worn off by then?
Oh blimee, me too... It used to be easy on the later commodores, just cut a new read only notch and flip it over. The BBC micro was not so easy, the beeb actually used the optical rotation index hole, so you had to make another one of those two... Which involved extracting the floppy bit, chopping the hole and then feeding the floppy bit back in.
Always seemed to get away with it though!
Probably an easy fix. A dry joint on the line output transformer can kill its drive transistor (and, if you are very unlucky, the transformer itself).
Re-solder all the joints on the Line Output Transformer (thing with the ferrite core and a HT cable coming out of it). Replace the big transistor next to it (Probably a BU208. Don't bother testing it. There may well be an internal resistance across B-E which will spoil your test results, it's probably about had it anyway and besides which, they are cheap).
Because, as you have a vertical line, you must have EHT for the CRT which comes from the line output transformer. This means the line output stage is working, its just the line scan coils that are disconnected, that will almost certainly be a dry joint on the PCB where the scan yoke leads connect or possibly at the scan coupling capacitor or line linearity coil. It can't really be much else other than an o/c scan coupling capacitor.
How do I know this? well, the college I worked for had lots of Osbornes and I used to repair them when they broke down. Most common fault was the extension card for the double density floppies working loose (these things were carried between rooms regularly which probably explains that), next was the display which could fail to work due to dry joints at the line output transistor connections or by the vertical line due to joints as described earlier.
Once I had to make a new system rom for one (by copying a good one from another machine) as the suspect one was partly corrupt (would boot to the Osborne startup screen but would intermittantly fail to load the o/s from disk) -- that took a while to diagnose.
One other task I had to do was calibrate all the floppy drives so that disks were interchangeable between all machines -- there were quite a few that would not reliably read disks from other machines until this was done.
Most of our Osbornes worked with external monitors (to ease eyestrain on the students).
When carrying machines between rooms I always carried two at a time, that way both arms stretched by the same amount :-) happy days indeed.
"If you've been around personal computers for a few decades, you'll remember when floppy disks were, well, floppy."
The really scary thing is, anyone who's born in the last 15-20 years will probably not even know what a floppy disk is/was, let alone whether it was truly floppy or not!
22 years old, and I grew up on floppy disks. Although that was probably because we always got the old equipment from other people instead of buying it all new ourselves. I even grew up gaming on a commodore 64 in the mid nineties. I still have it and will cherish that machine to death.
I know, I fall out of the age range with 2 years
I'm 20 and I used to use the terminals which managed the library system at primary school, the program was on 2 5 and a halves and were a nightmare to get working because the discs kept failing due to their age (they didn't even want to shell out for new disks). From what I know they haven't upgraded their systems yet... I also remember installing Fifa 95? (not so sure about the year) on the computers running 98SE we had there, Good memories.
...which was the original model in the tan and black case
If I remember rightly, it experienced the same 'green line of death', but he could carry on using it with the external orange-screen monitor he had. he finally ditched it when one of the floppy drives gave up the ghost.
I later furtively opened the thing up and tried to get the other driove working on the Amstrad CPC 464 we had. Apparently the edge-connector on this, although being the right size and shape, had some of the pins swapped, so I never got it to work. I would have been about twelve at the time, so I get the points for trying anyway!
Seeing the insides of one of these again after so many years brings back fond memories. I wonder whatever happened to the one my dad had...
And @CJCox above; I too remember the shrill cacophony produced by daisy-wheel printers, which I think can best be described as someone dragging a hessian sack full of broken china back and forward across some iron railings.
Yes, Commodore did a version of the C-64 in an Osborne-style case, called the SX-64. Like the Osborne, it had a 5-inch screen, although the Commodore's did colour. With one exception, I remember mine fondly, in a sad, geeky way.
The exception was the handle. The SX-64 was clearly designed to *look* portable, but it was also clearly designed in such a way as to discourage you from carrying it. The cylindrical full-width handle was decorated by a series of length-wise grooves that combined with the unit's considerable weight to leave grooves in your hand, and carrying it any distance was actually painful. Bah.
First of all, thanks for an interesting article and exploration. Some years back, I rescued an Osborne 1 from "Curbside Discount" along with a bunch of software. Apart from a burnt out bulb in the power button, it worked quite well. I certainly did not go as far as you did in taking it apart, mainly out of fear of breaking it.
If you can find a copy of Peter A. McWilliams' Personal Computer In Business book, it will be an interesting trip down memory lane...and I thoroughly enjoyed reading it. Mr. McWilliams was none too fond of the Osborne 1 and made that perfectly clear. He felt the screen was too small, the fan too loud (of which more later) and the character font unclear. His description of the screen's phosphor color was also not to be missed--"several shades of orange, not unlike a punk rocker's hair" IIRC. He also disagreed with Adam Osborne about screen size--Peter's thought being that bigger screens were the way of the future while Adam insisted that smaller screens would be all you'd see. In their own ways, I think both men were right.
(If anyone out there still has the supplement to this book that is mentioned at the back--I'd love to know about it. Likewise, I think there was a much later version published in the 1990s that I can't seem to find now.)
I was surprised to see that your system had what appeared to be a green phosphor display, and found the lack of a cooling fan interesting as well. Every O1 I ever saw had the cooling fan underneath a sliding door in the handle. I don't think there was a black and white version of the display--I definitely did not expect to see a green one!
As for the display, it's probably fixable. You should turn down the brightness and contrast dials before the screen gets a permanent line or a "belly button" burned into it. I would bet that the failure is either bad solder or dried up capacitors that have drifted far from specifications over the years. Bad solder could be determined by poking at the CRT board with a **well insulated** object. If you're not comfortable around very high voltage electronics, see if you can get a knowledgeable friend to help--and maybe you could owe them a favor or buy them dinner?
Anyway...that's a pretty cool walkthrough of the system. Thanks again for doing it and sharing the result.
As I type this we have an Osborne of this vintage on the shelf next to me. We had some people move offices in 2010 and they abandon some equipment when they did so resulting in an Osborne being unceremoniously dumped into the IT area. When we first picked it up it shook and rattled like it was full of loose screws; which is was. Apparently someone had been dropping miscellaneous screws into the heat vents over the last 20 years or so. Popped off the hood, dumped them all out, and was surprised to find that it booted straight up into CP/M on the first go.
I was still using GPIB in my last job in 2009. The daisy-chaining was cool (although the big-ass cables and connectors were cumbersome), but setting addresses via dip-switches or deep in instrument menus was not so cool. We used NI drivers because HP's didn't work for us.
Back in time we used a Philips P2000C which concept looks like quite similar to this one. Except for the bigger screen and 2 80 track floppies rightsided with an amazing 360 kb if remember correctly. With 80x25 lines, Wordstar,Calcstar and MBASIC it was a quite usefull computer albeit a little hefty to carry. Later on you even could get an MS-DOS co-powerboard and a 10 Mb HDD. Great machine!
Unfortunately the screen was damaged - the glass is actually cracked - whilst it was on its way to me.
Anyone know where I can get a replacement CRT? Or how I can actually hook up an external screen using that edge connector?
I do know that the computer itself actually worked (and I guess the review who wrote the article can try this too), because I hooked up a terminal to the serial port and used something like:
stat con:=tty:
It may not have been *exactly* that command, but it was something similar. Different CP/M boxes called their serial ports by different names.
Great article though. Please, someone, do one on the RML-380Z - I have a non-working one of those too :-(
If the actual CRT is physically damaged, don't turn that thing back on until it's replaced!
Very Bad Things could happen!
After donning protective eyewear and gloves, take a look and see if there's a piece of glass in front of the screen, and if that's what's damaged.
Better yet, find a TV repair shop with someone who's been in the business for years to check it out.
I own a osborne 1, Service Manual, Software and External VDU. Sadly I ditched the printer that came with it but this was a star. It was used in my Father in laws business. I also own a signed copy of Hypergrowth by Adam Osborne. The Power supply in this pc/laptop was an Astec which was very common in the mid eightys.
... thanks for yet another great article on homecomputer cambrian...
Even though I now do feel old considering I know DIP switches - I never had the pleasure of owning a Kaypro or Osborne, my portables were rather curious exotics such as the Epson HX20 or the Z88. Although I did own a Sanyo PC XT / 80186 portable, which was following much the same design as the Osborne...
CP/M wise I was always restricted to the robotron monsters of East German fame, sporting the U880, a Z80A clone. But good times nonetheless. WordStar, SuperCalc, dBII ... not to forget BASIC80 (basi?), TurboPascal, Ladder, Catchum ... and yes, POWER was the handiest piece of software in these days, as a matter of fact, it was so good, I think it wasn't until Norton Commander, that a software tool was such a versatile utility. I mean - come on! multiple file selection through sequential numbers - that was class! ;-)
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