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Please cry with me - My Osborne 1 chewed up my DD boot disk :( Advice sought.

I don't have the screenpak but I was wondering how difficult it would be to make one up, or at least something that did the same... Monitor the top 4K of memory with a small Dual Port static ram, and build a basic video driver. And a switch somewhere to switch between the two. It would be a shame to only have a single option.

Shift quote to switch disks? Nice. I noticed my early model seems to have a faulty keyboard and it did try booting of B once, but I didn't know what combination it changed upon.

I'd much rather have the screen pak, but it would be nice to make up something that did the same...

David.
 
Oh £$%

Been playing with my OS1 and suddenly Zork isn't running properly. Booted diags and its showing a faulty RAM at UC24 (but only in the GALPAT test, the others work fine). Will leave it running with the brightness turned down and give it a damn good testing (picture Basil Fawlty thrashing a Austin 1100 with a tree branch)

The very large number of RAM failures in this machine has made me suspect the PSU in the past but its looking all the more likely. Will be interesting to open it up and see if its one of the previously replaced chips or if its one of the originals.
 
It's all 4116's - I assume the -5v rail is not compromised? It is generated on the board but if it dies, will damage the chips slowly, even though they may function somewhat... It's on diagram 7 of the schematics in the technical manual, but you can measure it against pin 1 of the DRAM chips IIRC.

If the 5v and 12v from the PSU are stable and within a few tenths of a volt, then it's probably not the mains PSU - but it's always possible.
Also, 4116 don't age terribly well even with the best of power supplies.
 
Not opened it yet to see if its an original or new chip thats failing. However its either the original RAM's that have reached the end of life, or one line is slow coming up and exceeding the allowed diff and damaging them.

Or, of course, a bit of both :)

Thinking laterally though, I will probably replace any failing chips in the future with 4164's which require only a simple mod (pin 1 cut and pin 8 removed from the socket and shorted to pin 9) and are single supply so can't suffer the same. They use less power too.
 
So it was an original chip (that's 9 now), replaced with the same AMD device as I have a bunch of spares and they seem to work ok and none have yet failed.

Each one I have replaced I have also socketed so if they start failing too, a switch to 4164's will be quick and easy.

and Zork is working again :)

Going to leave it running mom diagnostics for a few hours now and see if any other chips fail.
 
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Ah, the great game of Zork. And being eaten by a Grue. I remember playing Zork on the pdp-10 at Penn State. I later played in on Commodore maybe TRS-80.
 
Well, isn't fate a funny bugger. Just found a screenpak board !

No idea if it works yet but when it arrives I wonder if I should try to Kicad it.
 
So all my original Osborne disks seem to be shredding, but some cheapies I got from Ebay seem OK. One shredded so far, but the others seems pretty stable and I even went as far as to continuously format one for about 30 minutes and it survived just fine... It was an interesting exercise - and here's what I noted.

1. I found an interesting file I never saw on any sites before on the original disk - Called the Osborne Audit Program which seems to be a presale test - jsut tests things like screen alignment and that all the keys work, but not as much as the other test program. I think it was called ET.COM or something like that IIRC.

2. Not all drives format old disks well. It looked like a coercivity issue, so I stuck some neodymes near the disk while the drive was running, and it helped... I ordered a proper degaussing want to degauss the disks in the future. Should help with coercivity issues on old disks.

3. Aside from needing a microscope to check the heads, they need to be checked frequently, so if I want to check a lot of old disks, I need to think of a convenient way to extent a cable from the Osborne and switch between an internal and external drive, because there's not telling which disks will shred ( I'm still waiting on the methicone lubricant mentioned ) -

4. The bearings are a problem. One disk needs some serious cleaning, and the other I took the plastic clamp apart and cleaned already. But one disk is so bad it doesn't always start without a push. I hope it's not a brush issue in the motor.

5. Stepper related issues caused more formatting errors that anything else - A little WD40 on the worm drive - just a drop or so - fixed that problem right up- I wouldn't have thought it was a stepper related issue until I noted it was having trouble going back to track zero but away from Track 0 just fine.

6. There are some easy ways to make the cable for a Gotek from the pieces as an alternative to the adapter PCB. Just some ribbon cable, two 34 headers, and a 34 edge connector and a razor knife is enough. And maybe some solder to break out the 5v line for the Gotek.

7. Two GOTEKs look like they could be a good option.

Well, I haven't made an announcement yet because it's not finished, but I'm working on a Gotek adapter for the Osborne 1 and any other machine with full height FDDs. Here's a short video of how it works so far ( I tried to make the drive look and feel authentic... Just messing with mounting options to hide the gotek behind the flap. )
Yeah, that motion is way too satisfying... It will last for hundreds of cycles ( it's spring loaded with a simple elastic band ).

 
I have just fitted a Gotek to my Osborne 1 this weekend. Used the pinouts from an older thread here on the forums to make a little PCB to switch the DS1 line between the A drive and the Gotek.

The problem i now have is that my machine can only read the lowest capacity disks and i have no system in my collection that can write FM encoding.
I was hoping that the archive of the First Osborne Group on Bitsavers was working but i can't get the IMD files converted to HFE files for the gotek. But the gotek was a very handy way to back up all the disks i got with the machine.
 

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So you need all the DD files converting to SD ?

There is an Osborne MAME emulator somewhere I believe that might be able to do that, or otherwise one of us will need to do the conversion (or find that hen's teeth DD adapter)
 
So you need all the DD files converting to SD ?
I don't know... i looked at the IMD file from bitsavers in the HxC software and the trackviewer looked like this:
Notworking.jpg

And the files i made by copying the disks to an empty HFE file look like this:

Working.jpg

I'm not an expert on this but track layouts don't match at all. And i have converted a TD0 teledisk file to HFE and it works fine (and it has the same 10 sector layout in trackviewer).

There is another archive with the same files ofcourse... but they are in .ARC format, I don't know if Image Disk can convert those to .IMD in a working layout. I have to see about that this weekend, this is the first time i'm working with a diskformat i can't read or write on any other computer.
 
Single Density = 256 byte sectors, 10 sectors/track 40 tracks
Double Density = 1024 byte sectors, 5 sectors/track 40 tracks.

Someone was building a double density adapter were they not? Hopefully the information I provided can assist them -

David
 
Double Density = 1024 byte sectors, 5 sectors/track 40 tracks.
Ah, I did not know that. Thanks for the information. (I kind of figured Double Density would mean 10 sectors at 512 bytes.)

I have seen the thread on the adapter recreation, I hope they can get working.
In the meantime I will have a search for an emulator and see if I can copy things from DD images to SD images.
 
Well, isn't fate a funny bugger. Just found a screenpak board !

No idea if it works yet but when it arrives I wonder if I should try to Kicad it.

So screenpac has arrived (attached to an OS1 motherboard with a double density adapter as a bonus)

Oddly, the jumper wires dont match what the manual says. The manual has two wires not connected but this one has them all connected.

Not sure if to spend some time trying to get the motherboard to work with the screenpac already fitted or to try to install it on my working machine.

It does look as this is a later screenpac as it doesn't seem to have the coax video connection but I have not found any reference to different versions in manuals.

Does anyone know of a later manual with installation instructions ?
 
If it was already on an O1 board, is it not already wired up?

I don't know about the missing coax - It seems you have something interesting on your hands. You could use a normal video out adapter to drive the coax if it's not there.
 
I can copy the setup (thankfully !) and then can try it, but it would be nice to have a manual that matches. there are two other sockets and I'm not sure what they are for :)

Actually, I think the instructions are in the service manual. It has two lots but doesn't quite explain the differences, but the earlier unit doesn't have a coax connection but also uses clips rather than direct soldering.

Slowly slowly :)
 
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What is happening with the old main board that came with the ScreenPAC? I assume you got it for the add-on PCBs - Was the main board faulty?

I am figuring to try logic analyzer clips when I make a build of the 80 column adapter I've been working on.

David
 
I don't know the state of the old motherboard apart from its missing one chip and a brightness pot so I assume its a bit dead and used as spares but it looks reasonable so might try to fix it. Not sure yet.

A full clone of this board looks fairly simple though. Given the circuits available and I could take some photos, it would just need someone to take the time to draw it out on Kicad.
 
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