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    • Having some 400k drive issues and hoping a resident expert here can help ...   A few weeks back I got out a classic old Mac boxed game (Dark Castle, if you’re wondering) and decided to play it from the disk on my 512k.  Annoyingly, the disk wouldn’t read, and suddenly neither would any other disk, so I took a look at the disk - the disk medium looked 100% fine.  I decided the 400k drive head must be dirty, opened up the 512k and thoroughly cleaned the head with isopropyl alcohol.  Still won’t work or recognize any disk at all (attached video shows what it does when I insert any disk on startup), and will fail to initialize anything inserted.  Now I make a mistake and decide, somewhat stupidly, that the disk is probably fine and I just had a weird sudden drive failure ... so I try the same disk in an external 400k drive.  All the same things happen.  Suddenly I’m worried I’ve ruined two of my drives with this bad disk!  Again, cleaning the drive doesn’t help.  So I open up the Dead Mac Scrolls and google around for help — I see various mentions of a “track zero alignment procedure” (the Dead Mac Scrolls, p. 274, says if you can’t even initialize a disk, it’s not a stepper motor misalignment but possibly a track zero sensor misalignment) but no good photos or specific instructions for a 400k drive (the Dead Mac Scrolls diagrams are for an 800k drive only, I think).  But anyway - how would I very suddenly experience track zero sensor misalignment only after using this particular disk?   By the way, I did something risky and tried the same disk again in a disused 800k drive I had lying around ... it also failed to read, and AGAIN the next disk I inserted couldn’t be read either ... however, in my 800k drive, running a normal cleaning disk with alcohol through the drive a couple times got everything back to normal and it’s now 100% fine.  Again, though, head cleaning didn’t help my 400k drives at all.   So - here are my questions:   1.  What the heck could possibly be wrong with this disk that it can ruin any 400k drive it touches (but again, looks entirely OK - it’s not like it’s shedding dust or the disk medium is visibly scratched or anything) 2.  What’s the proper and official way to clean the head of my 400k drives?  Since head cleaning fixed my 800k drive, I’d think that cleaning the 400k drive heads should work, but it doesn’t seem to ... do I need to do anything other than wipe the little white shiny head guy with alcohol? 3.  Is there anything else I should try, like this track zero sensor alignment procedure?  Is there a clear set of instructions for that somewhere, specific to a 400k drive?   Thanks for any help!   43F84BDC-9B40-43A1-BC28-2C2737C5250C.MOV
    • I might still have a spare from a parts G3 desktop I used to have, if your floppy drive truly is broken.
    • Quick update, got impatient and decided to just take some 70% ipa and clean the leak by the adb ports as it seems that is a common issue for soft power and it booted right up!   Will start removing the old caps this weekend, but always good to know its in a working state before you start.
    • Still no dice    I have noticed one bigger issue. In the Dead Mac Scrolls (Troubleshooting, flup-flup- issues, page 24) there is a description that one should be able to measure a lowish 31/30 ohm resistance over the CR20 rectifier diode. And 52/53 ohm across CR21. If I try to measure that on my board, I briefly get about the correct value but then it starts rising, and ends up somewhere over 2-2,5 kOhm. I can't quite figure out why, as I have replaced both CR20 and CR21, and the electrolytics around them.    Also adjusting R56 (+5V adj) fully counterclockwise (page 27) does not help the issue.
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