Well, that's certainly interesting! Dave sent this one off to be scanned, I don't know if he still has the original.
Dave, if you do still have the original, can you confirm if the trace is missing on yours, or if Mile High Test goofed?
Building an OSI 502B CPU Board
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glitch
- Posts: 176
- Joined: Mon Nov 28, 2011 12:43 am
Re: Building an OSI 502B CPU Board
Check out The Glitch Works
OSI Challenger 3, 510 CPU, 8" floppies, 23 MB hard disk system starting to work!
Parts bin Challenger 3 board set, never had a chassis in its time
OSI Challenger 3, 510 CPU, 8" floppies, 23 MB hard disk system starting to work!
Parts bin Challenger 3 board set, never had a chassis in its time
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dave
- Site Admin
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- Joined: Tue Sep 09, 2008 5:24 am
Re: Building an OSI 502B CPU Board
The original scans are up on Github: https://github.com/osiweb/Hardware/blob ... SI-502.pdf
This is my original 502 board, so it's had numerous mods over the years. It appears that I cut that trace at some point. It's part of the BASIC ROM addressing circuitry. I probably had a jumper somewhere, and when I sent it off, I removed all jumpers and marked traces that needed fixing with black lines (you can see some in the scan.) I must have forgotten to make a "black line" to indicate a trace that needs fixing.
Anyway, I'll fix it in the gerbers on Github, and on the archive.
Thanks for pointing it out!
This is my original 502 board, so it's had numerous mods over the years. It appears that I cut that trace at some point. It's part of the BASIC ROM addressing circuitry. I probably had a jumper somewhere, and when I sent it off, I removed all jumpers and marked traces that needed fixing with black lines (you can see some in the scan.) I must have forgotten to make a "black line" to indicate a trace that needs fixing.
Anyway, I'll fix it in the gerbers on Github, and on the archive.
Thanks for pointing it out!
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Jeff
- Posts: 370
- Joined: Fri Mar 07, 2014 4:44 am
- Location: British Columbia, Canada
Re: Building an OSI 502B CPU Board
Dave, Would it be possible to make a variant of the board that can be used with 2716s?
/Jeff
/Jeff
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Jeff
- Posts: 370
- Joined: Fri Mar 07, 2014 4:44 am
- Location: British Columbia, Canada
Re: Building an OSI 502B CPU Board
Here is another fix to the 502. This one seems to be a change to the original 502 board, modified at OSI, I think.
Here is the SAMS schematic, confirming the fix that the R75 POT DOES NOT connect to pin 6 of U22 (It connects to pin 7)
The other green jumper connects U3 pin 2 (RX DATA) to U23 Pin 5 to support the cassette IN/OUT.
/Jeff
- 502 Cassette Fixes.jpg (515.24 KiB) Viewed 47252 times
- OSI Fix Schematic.png (523.61 KiB) Viewed 47252 times
The other green jumper connects U3 pin 2 (RX DATA) to U23 Pin 5 to support the cassette IN/OUT.
/Jeff
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Jeff
- Posts: 370
- Joined: Fri Mar 07, 2014 4:44 am
- Location: British Columbia, Canada
Re: Building an OSI 502B CPU Board
Dave,
The above change (R75 from U22 pin 6 to pin 7) could also be included in the gerbers... call the board a 502B.2 or 502C?
/Jeff
The above change (R75 from U22 pin 6 to pin 7) could also be included in the gerbers... call the board a 502B.2 or 502C?
/Jeff
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Jeff
- Posts: 370
- Joined: Fri Mar 07, 2014 4:44 am
- Location: British Columbia, Canada
Re: Building an OSI 502B CPU Board
And today I got the 502 working!
/Jeff
- Working!.png (1.03 MiB) Viewed 47252 times
/Jeff
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waltermixxx
- Posts: 129
- Joined: Sun Feb 03, 2019 10:31 pm
Re: Building an OSI 502B CPU Board
That's awesome...
Turning into quite an OSI Junkie (HTFDTH?) Superboard II REV B-40K, 9600b, HC-05 Bluetooth, Superboard II Rev D, C4P rebuild- 502, 542c, 540B.
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waltermixxx
- Posts: 129
- Joined: Sun Feb 03, 2019 10:31 pm
Re: Building an OSI 502B CPU Board
Anyone going to VCF MW?
if so see you there, come by the COSMAC 1802 table there is where I will be,
I will most likely have my OSI 600 REV. D board there, and hopefully a fully built
colour board to show.
if so see you there, come by the COSMAC 1802 table there is where I will be,
I will most likely have my OSI 600 REV. D board there, and hopefully a fully built
colour board to show.
Turning into quite an OSI Junkie (HTFDTH?) Superboard II REV B-40K, 9600b, HC-05 Bluetooth, Superboard II Rev D, C4P rebuild- 502, 542c, 540B.
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glitch
- Posts: 176
- Joined: Mon Nov 28, 2011 12:43 am
Re: Building an OSI 502B CPU Board
I'll be there!
Check out The Glitch Works
OSI Challenger 3, 510 CPU, 8" floppies, 23 MB hard disk system starting to work!
Parts bin Challenger 3 board set, never had a chassis in its time
OSI Challenger 3, 510 CPU, 8" floppies, 23 MB hard disk system starting to work!
Parts bin Challenger 3 board set, never had a chassis in its time
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Jeff
- Posts: 370
- Joined: Fri Mar 07, 2014 4:44 am
- Location: British Columbia, Canada
Re: Building an OSI 502B CPU Board
I am uploading my parts list, and assembly notes etc. for those building one.
/Jeff
/Jeff