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IIGS recognizes 5.25" drives but not 3.5" or smartport? Help?!

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#51 spacecadet OFFLINE  


    River Patroller

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Posted Sat May 6, 2017 6:25 PM

Thanks! That is really helpful. I have a feeling your reading is a lot more normal than mine is. I've also asked Steve from BMOW to verify that my readings are not right since he seems like the guru of this DB-19 connector, so I'll see what he says too. I've actually got my fingers crossed that this is what's wrong; then it'll hopefully be a lot easier figuring out why it happened.

#52 Bloodnose OFFLINE  


    Star Raider

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Posted Sat May 6, 2017 6:49 PM

Glad to help someone so persistent.


I was horrified to hear your confession about hot-plugging.  For the love of God don't do that.  Not even the ADB.  Whenever I had to stop a hung process, with the drive light still lit, I'd power down, which lets everything ground out.  I highly doubt this equipment was engineered to handle hot-plugging, and even a power outage risked damage.


Can you trace those pins to an IC which can be replaced, though with quite a bit of solder work.  It still makes you consider if it's worth replacing an IC from a working board.  The possibility of getting new replacements with exactly the same characteristics is daunting.

#53 Keatah OFFLINE  


    Missile Commander

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Posted Sat May 6, 2017 11:14 PM




Page 4, upper left, of the 256K schematic shows most of that connector going to the IWM - which is your disk controller chip. 6 goes to 5V and 10 goes to the sense line.

Attached File  New-1.png   123.89KB   3 downloads


Additionally you can try running the built-in diagnostics. I don't know whether or not they query the IWM. And if they do, how far into it they go. Mine don't show errors, but then it's all working. Worth a try.

Hold down both <Open-Apple> & <Option> keys while turning on the power.


There are more advanced diags on disk, but considering...!!

Do you have any disk controllers of any kind that go into the slots?


#54 spacecadet OFFLINE  


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Posted Sun May 7, 2017 12:25 AM

Well, I more or less ruled out pin 10 tonight - copy protected 5.25" disks are still copy protected, while non-protected disks aren't, which is supposed to not be the case if that pin is shorted. I suppose it could be intermittent.


I now suspect the VGC chip. I traced the output from pin 4 and find that it terminates at the top right pin (not sure of the #) of the VGC. I then looked up the VGC chip by part #, not initially knowing what it does, and found this thread on another site: https://68kmla.org/f...drives-bad-vgc/


Interestingly, he also thinks he might have done it himself (or rather, his son did it) hot-swapping by mistake.


I definitely feel like I'm on kind of a wild goose chase here but everything's bringing me a little closer and a little more confident in the real culprit. I no longer really suspect my PSU, I think my drives are ok, I think the Floppy Emu is probably ok. I think the two most probable culprits are either an intermittent or near-short on pin 10 of the floppy connector, or a bad VGC chip. But the fact that it happened on both boards suggests that the most likely root cause is me pulling something out when I shouldn't have.


Apparently some earlier boards, including ROM 01's, have socketed VGC's. Unfortunately neither of my boards do, so I can't really fix them. But I'm going to be *extremely* careful when I get the new board.

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