IIc internal drive writes weakly

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IIc internal drive writes weakly

Hi everyone here,

The internal 5.25" drive in my IIc is having an issue a bit like some posted here and elsewhere but mine is a little different. It can read old disks perfectly, but when trying to write a new disk it is what I can only describe as "weak". It can almost be read back but when reading there are randomish errors that will occur. It does this with every disk I have tried so far. I even opened a "fresh" NOS package of "new" disks and it does the same thing. It also passes the self test. Unfortunately I can't make a Cillin disk of course to do some more thorough testing. Also the disks will not boot at all either.

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Have you cleaned the head?

Have you cleaned the head?

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...and checked the speed?

...and checked the speed?

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Cleaning

If out of cal speed can cause something like this I will definitely check that and calibrate it if necessary. As for the cleaning, I'm fairly sure I cleaned the head last time it was put away but I was about to clean it again anyway just to be sure. If you have ever brought back a VHS machine from a scren full of static with only a cotton squab and IPA you know how important it can be. Thanks for your replies. Hopefully it will set me in the right direction.

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The problem still persists

The problem still persists after cleaning with IPA and adjusting the rotation speed with a timing light. One strange thing is that sector 0 always has errors no matter what but then as the head gets closer to the hub it gets much better according to ADTpro. Besides going through the disk II bulletin I don't know what else to do except I don't have IIc 5.25" external drive and looking on eBay they are quite expensive. I don't have a 3.5" UniDisk either but the alignment disk image is for a 5.25" disk anyway.

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You don't neeed the IIc

You don't neeed the IIc specific external drive. The Apple 5.25 drive which is fairly plentiful and cheaper will work. Just don't try and daisy chain off it. 

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Are you certain that the

Are you certain that the diskette media itself is fine?

 

If it reads poorly at track zero and fine on the inside tracks, that smells to me like you've picked up mould on one of your diskettes and it accumulated on the read-write head.

When that happens the drive proceeds to grind a scratch into track zero of every subsequent diskette you insert into the drive, progressively getting worse as it goes, until you clean the crud off the read-write head.

Examine your dieskettes - is there (even the beginnings of) a concentric scratch near the outer perimiter of the media?

 

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Many of your symptoms are

Many of your symptoms are consistent with attempting to use HD diskettes, which are not compatible.  The Disk II can record on SD and DD media, but not HD.

Generally, HD diskettes can be distinguished by examining the hub of the disk:

  • SD and DD diskettes (single-density and double-density) generally have a reinforcement ring attached to the top side of the disk at the hub.
  • HD diskettes (high-density) have a plain hub, without the reinforcement ring.

 

An Apple Disk drive won't record reliably on HD disks because of their higher coercivity.

Errors tend to concentrate on the outer tracks, where the linear velocity is highest, as demonstrated by this Locksmith write-and-verify test:

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S.Elliott wrote:Many of your
S.Elliott wrote:

Many of your symptoms are consistent with attempting to use HD diskettes, which are not compatible.  The Disk II can record on SD and DD media, but not HD.

Generally, HD diskettes can be distinguished by examining the hub of the disk:

  • SD and DD diskettes (single-density and double-density) generally have a reinforcement ring attached to the top side of the disk at the hub.

That explains it then. I just looked at these disks and they are all high density. I've had them for a while and it's strange I never noticed it. Wikipedia says the coercivity of HD are twice that of DD. In theory doubling the voltage into Q2 would allow them to work but I don't want to ruin anything, especially the semi precious heads. Maybe it could be a mod but it's just a theory. Maybe I should invest in a flash memory drive.

Anyway thanks for all your helpful comments. I'm going to do battle with eBay again and look around for something Arduino that connects to either the 20 or 19 pin disk ports if such a thing exists. I may end up probing around with the "sillyspoke" to see what goes on down there.

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Nothings wrote: Maybe I
Nothings wrote:
 

Maybe I should invest in a flash memory drive.

The Floppy Emu is highly recommended and gives you a basic hard drive option at the same time. 

(Unless your IIc is a ROM255. Then you'll need a ROM chip upgrade) 

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