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Osborne 1 "BOOT ERROR" on Drive A: only, help diagnosing..

T

tendim

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Aug 11, 2018
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I have an Osborne 1 that I purchased sometime last year, and it was working great until one day it stopped booting. Inspecting the original floppy controller it looked quite dirty (overheating?) and I managed to source two new floppy controller chips and tried both (on the odd chance that they both had issues).

As of now:

  • System has the double density add-on board
  • System turns on, and boots from Drive B (using shift-quote to boot from second drive)
  • I have tried two new floppy controllers, issue persists
  • I have swapped the physical drives, and the problem persists

I feel that I've ruled out a bad controller, and the physical drive, since it boots fine from B: drive regardless of the physical drive that is there.

Any ideas where else I can look?

Thanks,
-10d
 
As this is your first post (even though you have been a member since 2018) welcome to VCFED.

Dirty just means it’s dirty... Overheating can generally be detected by things being blackened. English fails me in describing the difference though...

If it boots from Drive B:, and Drive A: boots when it is moved to the Drive B: position, then this probably indicates a problem with the drive select logic as opposed to the floppy controller.

These signals come from UC15 pin 16 (PB6) Drive select 1 and pin 17 (PB7) Drive select 2.

They are inverted by UA9 to become the drive select lines (pins 10 and 12) on the 34 pin floppy cables.

If you try to boot from drive B, you should observe Drive Select 2 changing state when the drive is selected. Conversely, if you try to boot from drive A, you should observe Drive Select 1 changing state.

Incidentally, the technical manual is here if you haven’t got a copy https://www.esocop.org/docs/Osborne1TechnicalManual.pdf.

Just make sure you identify the correct board revision before use.

What test equipment do you have?

Does what I have written make sense, or do you want me to simplify it a bit more? Just trying to gauge your level of knowledge...

Dave
 
Hi, any update about this issue ? I'm just facing about the same...

I'm worrying about moved something by error on drive A in moving the head by hand to lubricate (the Osborne was'nt use for a while)

Thanks for your king help and warm regards from France
Stéphane
 
Since the OP was last seen when they posted the message - I would probably say there are no further updates (nor will there be either).

Dave
 
I had an osborne-like drive in a Kaypro - same mechanism. Anyway, it failed due to grease going solid int he drive... I just cleaned it with some WD40 and it was OK.

If driveB boots, then possible issues;

* Drive terminator incorrect.
* Drive head misaligned.
* Drive head dirty ( common when reading old disks, but easily manually cleaned ). Can be seen with microscope, but otherwise try cleaning it.
* Drive electronics faulty.

Anyway, if B works, try running drive diagnostics on A from B. Can you format at disk? Can it be read back? Does that disk work in B?

As long as it's booting, you don't need to look for electrical issues until you exhaust all the tests you can do from within the OS. The Osborne 1 boot disks came with disk diagnostics IIRC?
 
cj7hawk said:
Anyway, if B works, try running drive diagnostics on A from B. Can you format at disk? Can it be read back? Does that disk work in B?

As long as it's booting, you don't need to look for electrical issues until you exhaust all the tests you can do from within the OS. The Osborne 1 boot disks came with disk diagnostics IIRC?
Click to expand...
Hi,
First many thanks for this quick reply and for your time already spent in helping me <3

I guess My Osborne 1 v2 (OS v1.44) stayed a long time without activity. I first replaced the Rifas, cleaned the A disk head and made a first trial.
The A drive made too much strange noise and I had a "bad sector" error.

I had no disks at all with the Osborne but as it has the Double density option, I succeded in making one CP/M disk with Teledisk (the only double density image I found in the Ozzie retroarchive pack. (This disk is actually booting well from B drive)

Cleaning the head and lubricating the guides/axes wasn't enough to reduce the working noise, so I put a drop of oil on the no-end screw and moved the head by hand to access closer to the motor.
Then the noise goes in disappering, and I finally succeded in booting from A: one or twice.
But yesterday, when I tried back again, the head is moving a bit from zero and return to zero witout end and each time it shows "BOOT ERROR" on the screen, which is different to "Bad sector" I had initially.

My guess is that maybe I disaligned something when I moved the head my hand ??

Many thanks again for your precious and kind help
Stéphane


Can you format at disk? I don't know if I can do from the CP/M disk only ?
Can it be read back?
Does that disk work in B? how could I test drive A from/after booting from B ?

The Osborne 1 boot disks came with disk diagnostics IIRC? I do not have the diagnostics disk, I guess the TD0 Teledisk image is SSSD and I cannot write one from my XT pc.
 
The heads are pretty solid.... The whole drive is pretty solid for that mattter.

Look for bits of magnetic material that have shredded onto the disk surface. They will be microscopic, but will prevent reading.
 
so you recommend to re-clean the head only ? What about others questions, tests, creating diagnostic disk etc. Thanks a lot again for your time;
 
Well, its possible you've damaged the drive, but they are pretty solid, so assuming you haven't misconnected any cables, etc, you can take the drive out and run it outside the machine, and watch it.

Usual checks.

Look at the strobe pattern under your lights to see if the speed is right on the flywheel. Move the head up a little before inserting the disk and make sure the head is seeking to track 0 and stopping there, and you can check the track0 signal with a multimeter on the pin. Get an oscilloscope to see data coming from the head. Make sure the terminator is in place and correct in Drive A and not Drive B. ( It should be ).

But I had an old disk, and it shredded *every* time I used it. I took pictures of what it left behind with a microscope and posted them here. And that caused damage to every new disk I stuck in there too.

Once you've checked all that, cleaned the heads, and it looks like it should work, then install a new disk and try formatting it. If it formats, copy files to it. If that works, see if Drive B can read it.

All kinds of stuff can happen when you can't see the drive. The transfer belt might have come off. The head might not be sitting right. And when you unplug the upper PCB, there's a lot of cables, and if I recall, a few pins that don't get connected. That's a recipe for mistakes on reassembly. And these things get 12v so damage might occur. I don't know what the extra pins on the pin header do.

Testing a drive isn't difficult. It's just methodical. Take it slow. Then once you've eliminated all the simple stuff, get an oscilloscope and watch what happens compared to the working drive. Things like a misaligned index sensor will prevent your drive from working.
 
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