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Unique S-100 computer (Z-80/Vector Graphic/Micropolis)

MikeS

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You can pick out the pattern even with an incandescent bulb. Not as obvious as fluorescent, but it’s there.

Mike

True enough, but incandescents are getting as hard to find as 'real' fluorescents and certainly not nearly as clear. But if that's all you've got...

BTW, Mike, let me take this opportunity to thank you for your many contributions to the hobby!

m
 

nullvalue

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LOL I did do this with a real fluorescent fixture - I had one for plants/seed starting - not CFL or LED. :) I swear I can't make out any pattern at all.
 

deramp5113

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We can rough check timing with a scope. Measure sector to sector time by monitoring test point 3, negative edge triggered. Note you’ll have a half-sector time slip in periodically at the index pulse. What interval do you measure?
 

MikeS

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LOL I did do this with a real fluorescent fixture - I had one for plants/seed starting - not CFL or LED. :) I swear I can't make out any pattern at all.

Well, there is the possibility that the speed is too far off; time to check it the hard way as Mike suggests ;-)
 

nullvalue

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We can rough check timing with a scope. Measure sector to sector time by monitoring test point 3, negative edge triggered. Note you’ll have a half-sector time slip in periodically at the index pulse. What interval do you measure?

I'm not sure I have my scope set up to capture this correctly, maybe you can make sense of this? I've recorded what TP3 looks like during the boot loop. Volts/Div is set to 1V, Time/Div is 2ms.

https://www.youtube.com/watch?v=Q72uuYmHDow
 
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deramp5113

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The flicker is the full rotation index pulse at 1/2 the sector time that you have to ignore. Looks to me like that drive is about 5.2 divisions or 10.4ms. That’s way too quick, nominal is 12.5ms (300 rpm, 16 sectors). See if you can adjust R89 enough to get the drive to 12.5ms (6.25 divisions). Then you should be able to see the strobe pattern and do final adjustments.

Mike
 

nullvalue

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Thank you, that helped me get it dialed in! I couldn't see a pattern at all, frustrated I tried under my normal LED bulb lighting and behold, a spinning pattern! I adjusted until the pattern holds steady, as can be seen in this video:

The outer pattern holds still (that's what we wanted, right?)
https://www.youtube.com/watch?v=kt9ZcF1eL2U

However, I went through the whole disk creation process now - twice - and same results as before. Disk writes successfully, but then (B)oot just sits there spinning the disk. It finds track 0 but then just spins.
 

deramp5113

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Well damn, yep, that’s correct. Post pictures of the Micropolis controller board mods. If the motor mod is done (that one stops the motor about four seconds after the drive is deselected), but the “ready mod” is not done, CP/M disks don’t work. Did you ever try the “ CPM22A-MikeD.VGI” disk images instead?

Mike
 

nullvalue

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I will try the other disk images. In the meantime, here are some closeups of the controller board - can you tell which mods have been done?

20200601_211452.jpg 20200601_211504.jpg 20200601_211525.jpg

20200601_211535.jpg 20200601_211541.jpg 20200601_211546.jpg
 

deramp5113

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here are some closeups of the controller board - can you tell which mods have been done?

It looks like the motor on/off mod and the ready mod are both implemented, so that's not the problem. Let me know what happens when you try the other disk images.

Mike
 

nullvalue

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It looks like the motor on/off mod and the ready mod are both implemented, so that's not the problem. Let me know what happens when you try the other disk images.

Mike

I know I tried the other images before with the same results. But now I'm not making any progress writing disks again. It starts accepting data over XMODEM, hits the first write block, the drive spins and clicks a few times (never did this before) and then write fails. Will keep playing with it.
 

nullvalue

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So something happened the other day I was hoping was unrelated but maybe it was.. I had a probe hooked to the drive board, went to roll my chair and poof something sparked, blew a fuse on the drive's power supply. Ugh.. replaced the fuse, everything seemed to be working fine. I swear I even had it "attempting" to write again after that, but I can't remember now. What should I be looking for? again.. Before it would go to write, the head would advance and it would at least think it was writing data. Now its like I'm back to square one where it goes to write data, but then fails..What got that to work before was swapping the head connectors on the board.. double checked that.. tried both drives, tried swapping the drives physically, too. The head snaps down now, it clicks a few times - then fails to write.
 
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deramp5113

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You mention, "went to roll my chair..." Did you end up pulling off a probe that shorted against something and "poof something sparked," or without being disturbed, did something go poof? If the latter, it's probably just a tantalum capacitor that died initially in a shorted condition that blew the fuse, but then finished open after it burned. If a probe or something caused a short bad enough to cause a poof and a spark, then that will be much harder to find as an IC or component or two is probably damaged.

Mike
 

nullvalue

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Yeah meant to say, when I rolled the chair, the probe was tangled around the arm and yanked the probe. I didn't exactly see if there was a spark as I had looked away. When I say poof I was referring to the fuse. :) I know, I'm not giving you much to go on.
 
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