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Osborne 1 questions

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generic486

Experienced Member
Joined
Mar 30, 2012
Messages
290
Location
Australia
I'm getting into the CP/m side of things now. I like the Osborne 1. I have a past history with Osborne. The first computer I ever got was a Osborne Turbomate IV.
But i want to ask a few questions before I get one.
First question, it has a CRT, is there much risk of electricution? I have a Mac SE, i know what's involved but is it any more dangerous?
Second question, how reliable are the machines? What is the most common problem with the machines?
Third question, should I get the Osborne 1 or 1a?
Final question, I live in Australia, and run 240V but some Osborne 1's I have seen in Aus have 120V, is there an switch or something to change the voltage or will I need a stepdown converter?
Thanks guys.
 
generic486 said:
I'm getting into the CP/m side of things now. I like the Osborne 1. I have a past history with Osborne. The first computer I ever got was a Osborne Turbomate IV.
But i want to ask a few questions before I get one.
First question, it has a CRT, is there much risk of electricution? I have a Mac SE, i know what's involved but is it any more dangerous?
Click to expand...

Short answer, it's about the same. Anytime you're dealing with crt's expect high voltages and enough amperage to really HURT or KILL! The Ozzie monitor is smaller, so the associated voltages are somewhat lower, but the really important thing is the current contacting you.

generic486 said:
Second question, how reliable are the machines? What is the most common problem with the machines?
Click to expand...

Generally they're extremely reliable. Major problem is caps on the power supply dying. Another problem is keeping the drives clean! Older disks tend to shed oxide which coats the read/write heads.

generic486 said:
Third question, should I get the Osborne 1 or 1a?
Click to expand...

Whichever you can find! Original tan case machines are a bit harder to find. Innards are essentially the same. The tan case is a bit easier to filet, but can be a bit of a bear going back together making sure wiring is scuffed and shorting. And getting the handle plate back in place!

generic486 said:
Final question, I live in Australia, and run 240V but some Osborne 1's I have seen in Aus have 120V, is there an switch or something to change the voltage or will I need a stepdown converter?
Click to expand...

Tan cases needed to be pulled apart to set a jumper on the power supply for 240V. IF I remember correctly the later models had a red switch located next to where the power cord plugs in to change over to 240V without opening the case. Of course, I could be wrong as I don't have my machine in front of me right now! :biggrin:

Thanks guys.[/QUOTE]

Either way, good luck in finding a machine.
 
curtis said:
Generally they're extremely reliable. Major problem is caps on the power supply dying. Another problem is keeping the drives clean! Older disks tend to shed oxide which coats the read/write heads.
Click to expand...

Could you tell me more about this problem? Because my Osborne 1 must have something related to that... when I first received it, there was a set of original disks which were unreadable. I then rebuilt new floppies from original images using my setup (a PIII with a Tandon TM-100 drive from an old IBM XT) and initially the Osborne booted (hurrah!).

After a few tests though, things started going worse and worse, and now it doesn't read anything anymore. I thought it was a misalignement problem, when a drive can only and only read what it previously writes, but when I disassembled the Osborne to hook the drives to my PIII... surprise! I found two (Siemens?) drives who get power from the flat connector, unlike the Tandons and usual PC drives.

I attempted cleaning the heads with alcohol (not isopropyl because its sale is regulated here) but nothing changed. Any hints about where to act in detail?
 
Isopropyl alcohol is good, but if you can find a floppy cleaning kit (probably on ebay) it uses a different solvent and generally works real well.

You might also check the speed on the drives. Pull the system out of the case and flip the drives over so you can see the belt and the drive wheel. There are 2 rows of "stripes". One for 60Hz and 1 for 50 Hz.

Turn the machine on and use a flourescent light or strobe light and hit the enter key so the drives start spinning. When the drives are spinning, one set of stripes should appear to be standing still depending on your voltage. If neither one is standing still, you'll need to adjust the speed. This is done by a small potentiometer using a small screwdrive. Don't twist it hard, just a little at a time until you get the speed adjusted correctly.

If the 2 above tips don't work, you may need to chance out the drives. Your options are pretty obvious:

1. Find original drives that get power via the ribbon cable. Not easy, but doable on ebay.
2. Find an upgrade board that allows for the use of standard drives. Pretty difficult, but if you can find a Nuevo board jump on it! The kit allows for not only standard drives, but double sided, and even quad density 3.5" drives. Quad density up to about 800K is pretty nice!

Good luck with the restoration.
 
curtis said:
You might also check the speed on the drives. Pull the system out of the case and flip the drives over so you can see the belt and the drive wheel. There are 2 rows of "stripes". One for 60Hz and 1 for 50 Hz.
Click to expand...

Right, forgot to mention it, but I seem to remember that when I did the tests I also tuned the speed. Definitely a misalignment or some nasty sort of dirt or something worse...

1. Find original drives that get power via the ribbon cable. Not easy, but doable on ebay.
2. Find an upgrade board that allows for the use of standard drives. Pretty difficult, but if you can find a Nuevo board jump on it! The kit allows for not only standard drives, but double sided, and even quad density 3.5" drives. Quad density up to about 800K is pretty nice!
Click to expand...

Maybe I could build an adapter, if I find two pieces of card-edge board (does vintage computing allow sawing the board of useless 1.2MB drives? :D ), where the power pins are rerouted towards a standard molex connector. Still, I would not know if the logic can be interfaced to a common PC floppy controller... I couldn't find much info about those Siemens drives :(

Ok, entry No. 1203493985 in the ToDo list :)
 
Do they have Tandy Electronics or an equivalent in Italy? I know the Radio Shacks here have a small perf board for little projects like this. That or you could check out jameco.com or some other electronics supply.

I've used Jameco quite a lot for oddball type stuff. They've got the headers like you'll need and probably the perf board also. Of course, don't know what shipping would be to Italy!

That's another problem, finding out what pins go where! Ground is usually fairly easy to figure out as about half of the pins will all be shorted together! Still figuring out which pin is read, write, step, etc. could drive a person to drink!

I'll dig around in my stuff and see if I can find any references for the pin out on the drives.

Anyone else got a suggestion for this user?
 
Osborne floppy pin-out:



1 GND
2 GND
3 GND
4 GND
5 GND
6 GND
7 GND
8 INDEX
9 GND
10 DRIVE SELECT 1
11 +12 volts
12 DRIVE SELECT 2
13 +12 volts
14 NC
15 +12 volts
16 4mhz clock
17 +12 volts
18 DIR
19 GND
20 STEP
21 +5 volts
22 WRITE DATA
23 +5 volts
24 WRITE GATE
25 +5 volts
26 TRACK 00
27 GND
28 WRITE PROTECT
29 GND
30 READ DATA
31 GND
32 SIDE SELECT
33 GND
34 LATE

patscc
 
patscc said:
Gabriele72 said

Glad to help. Keeping posting how it works out.
patscc
Click to expand...

I have compared the pinout with a standard Tandon TM100, it seems both drives use a similar pinout, they only replaced some GNDs with four +12V lines and three +5V lines on the lower side of the connector. However, there is a couple of pins I don't know exactly what to do with:

Pin 34 is named "LATE" on the Siemens while there's a connector clamp on the Tandon. What could it be?
More important, could you please doublecheck pin 16? The tandon has MOTOR_ON there, while your pinout reports a 4Mhz clock... :confused:
 
Okay, I dug up a technical manual for the Osborne 1.
The pinout is correct. The reason it's so odd is the Osborne uses it's own drive drive control board, instead of the stock Siemens one.
The oddity is that I think they stuck the some of the write-precompensation circuitry on the drive board, and not on the floppy controller board (i.e. motherboard),hence the LATE line.
I *think* connector clamp is a disk change signal, although I need to dig into it more.
patscc
 
Well, I swapped the drives and reconfigured B as A by swapping the (termination?) resistor pack, I don't know if it's all that is needed, but it did work. Former drive B works much better, I can boot 4 out of 4 disks that I have made with 22DISK, format and copy. The other drive however has severe problems that go beyond my diagnostic skills. I cleaned the head, tuned rotation speed and cleaned the flat contacts, but it works randomly. It seems as if at times it's not getting some of the commands properly. Most of the times I simply get a BDOS error.
Something I experienced:

- Using COPY wouldn't write beyond track 2.
- Format worked at times only, better when choosing single density.
- Moved back as drive A, on power on it comes up with motor running and led on (the other drive when configured as "A" keeps quiet until I press enter).
- Moving the connectors may improve (or worsen) the drive behaviour.
- Once I reassembled everything, the drive wouldn't spin on access.

Could be any component or bad soldering somwhere... :mad:
 
patscc said:
If you're feeling brave, you could swap the drive controller boards, and see if the problem is on the board, or something else.
patscc
Click to expand...

Tried that too, seems the problem is in the board... I'm afraid without an oscilloscope my tests end here.
Besides, the plastic piece holding the LED for index hole detection broke in two from age... and I had to carefully glue it back. Definitely not my lucky day.
Oh well, I should be happy enough I can now play with my Osborne, although with only one drive working :)

However, I'm afraid it wouldn't be possible to easily interface a Tandon to the Osborne or a Siemens drive to a PC. I wouldn't know how to drive the motor_on signal.
 
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