Internal Drive in Mac Plus not reading, what do I look for taking it apart?

[RoadWarrior]

The built in drive from my Mac stopped working, insert disks but won't boot from them(just ejects them), I have to use the external drive to boot. After boot it says disks can't be read and wants to erase the disks. But they do work in the external floppy drive just fine. I was planning to look inside the Mac anyway soon, any idea what I should do to fix it?

 

[Soupwizard]

Get this book: Macintosh Repair and Upgrade Secrets, it has all sorts of great info on fixing and maintaining early macs. (obviously, buy a used book, the new price is a bit high

 

[RWallmow]

The built in drive from my Mac stopped working, insert disks but won't boot from them(just ejects them), I have to use the external drive to boot. After boot it says disks can't be read and wants to erase the disks. But they do work in the external floppy drive just fine. I was planning to look inside the Mac anyway soon, any idea what I should do to fix it?

I would try the simplest thing first and run a cleaning disk in it. If you try to clean the heads manually with swabs and alcohol, just remember to NEVER, EVER pull up on the top head assembly, you will mess up the tension spring and its a real bastard to get back into tension (I have never successfully fixed one, but others have).

Other than dirty heads, usually all that goes wrong with the SONY Mac drives is inject/eject mech and head screw-gear lube dries out, little WD40 helps clean old dried lube, and some new lithium or silicon grease on the mech.


Failing that, the actual drive mech is the same internally, in the built-in, and external drives, if you would rather have the working internal drive you could just swap the drives. You can also purchase and use a 2MB (1.44) SONY drive mech it will just be recognized as an 800k drive by the Mac Plus's floppy controller (IWM chip).

 

[RickNel]

I have just had exactly this problem. I've been advised that the symptom usually points to a short circuit in the filter chip that sits on the logic board just behind the internal floppy port. It is clearly marked FILTER. If shorted, this results in the pin that selects the external port remaining permanently high, so bypassing the internal disk.

I've yet to do this, but the advice is that if you remove that filter chip, the internal drive will function but the external one won't. On my Plus logic board, the filter is a Bourns 4120R RC network, 20-pin DIP. You can replace it, or build yourself one on a 20-pin DIP socket following the schematic available on the Bourns website, using sixteen 25R resistors and eight 200pf capacitors. I think the replacement is available from serious electronic stockists.

FWIW I think I shorted this filter by (experimentally) attaching a 3.5" Superdrive to the internal connector. Pin 9 on that connector is -12v for legacy drive pullup purposes, and should not be connected to a Superdrive, which will ground it. I suspect this drew a serious overcurrent through the connector. The logic board generally was protected by the analog board "fluffing" overcurrent circuit-breaker, but the filter is likely to have failed.

I'll get to removing the filter in the next few days to see if this advice is correct, then check replacement options.

EDIT: Removing the filter has not solved the problem for me - more to study about where signals are going between the drive and the IWM chip.

Rick

 

[RoadWarrior]

Thanks for everyone's input! Hopefully it is just the heads that dirty, I do not have a cleaning floppy so I will probably have to still take it apart. I noticed when pushing in disks, it doesn't have that loud THUNK sound as much, still grabs the disks though and ejects them fine.

 

[RWallmow]

Thanks for everyone's input! Hopefully it is just the heads that dirty, I do not have a cleaning floppy so I will probably have to still take it apart. I noticed when pushing in disks, it doesn't have that loud THUNK sound as much, still grabs the disks though and ejects them fine.

Be careful cleaning the heads if you are taking it apart, its crazy how little force it takes to trash the tension spring in the top head.

The drive not going "THUNK" is probably dried grease on the inject/eject mech, I would clean up the dried grease and re-lube it * while you have it apart, wont be long till it starts getting sluggish ejecting and you can grind up the eject motor gears if it gets too bad, and those aren't fixable (unless you have a 3D printer or something to make new gears).



*WD-40 is GREAT for cleaning up dried grease, but it is NOT a proper lubricant, its made from light oils, not what you want to use for permanent lubrication, its purpose is cleaning stuff and displacing water. As a lubricant it will break free stuck parts but will only last a few days at best and leave you with grinding metal causing wear that is not fixable. The proper lubricant for the drive would be like a Silicon or Lithium grease, both would be pretty effective, I believe they came factory lubed with Lithium grease.

 

[RWallmow]

http://vimeo.com/14581224 Here is a great video from Tony Diaz at Kansasfest on disk drive maintenance (starts about 5min into the video). It should help a lot with your drive, the mech is the same even though he is working on an external Apple II 3.5" drive.

 

[RoadWarrior]

Thanks again, not sure when I will get to it, only place that has a torx screwdriver comes in a set and was almost $40. I'm not paying that much for a screwdriver but I found out there is a vintage computer club next week and will see about maybe one of them might have the tools as I see some have Macs.

 

[geoffm3]

I have the same problem on a newly acquired Mac Plus. It spits the disk out and won't attempt to boot. I haven't tried to erase a disk yet with it, but the heads looked clean.

 

[geoffm3]

Thanks again, not sure when I will get to it, only place that has a torx screwdriver comes in a set and was almost $40. I'm not paying that much for a screwdriver but I found out there is a vintage computer club next week and will see about maybe one of them might have the tools as I see some have Macs.

Fleabay has the right torx bit that you need... 6" or 8" long and with shipping it's like $6 or so (extra long T-15). You don't need any other size.

 

[RWallmow]

Just an FYI: I didn't touch on this before in this thread, but you NEED to use DSDD disks, 1.44MB DSHD disks down-formatted (HD hole taped over) to 800K just do not work reliably, even if you get it to work once or twice, it will not continue to work. Something to remember while working with a Plus (or any other 400/800k equipped mac).

 

[RWallmow]

Fleabay has the right torx bit that you need... 6" or 8" long and with shipping it's like $6 or so (extra long T-15). You don't need any other size.

I bought a "craftsman" Torx set from Sears and it has a JUST long enough T15 to hit the screws in the handle. Want to say it was like $20-30 for a set of like 4 or 5 T10 through like T30 drivers (including the needed T15). I don't mind spending the money on tools, I figure I will need them some day, sooner or later, so its an investment ;-)

 

[geoffm3]

I bought a "craftsman" Torx set from Sears and it has a JUST long enough T15 to hit the screws in the handle. Want to say it was like $20-30 for a set of like 4 or 5 T10 through like T30 drivers (including the needed T15). I don't mind spending the money on tools, I figure I will need them some day, sooner or later, so its an investment ;-)

I hear ya. For me, I've got about two complete sets of Torx bits, but of course the hole is too small under the handle to use a bit, so I ended up having to buy an extra long one to fit.

 

[geoffm3]

Just an FYI: I didn't touch on this before in this thread, but you NEED to use DSDD disks, 1.44MB DSHD disks down-formatted (HD hole taped over) to 800K just do not work reliably, even if you get it to work once or twice, it will not continue to work. Something to remember while working with a Plus (or any other 400/800k equipped mac).

In my case I've tried using half a dozen DSDD media. The same floppies work reliably in two other Mac drives, but not this one. I think something electrical on the drive might be toast.

 

[RWallmow]

In my case I've tried using half a dozen DSDD media. The same floppies work reliably in two other Mac drives, but not this one. I think something electrical on the drive might be toast.

If you are sure the heads are clean, you could have heads out of alignment, that's pretty easy to check though if you can boot the mac on an external drive you can usually format a disk with out of alignment heads and still read/write to that disk on that drive, just wont read other Macs disks and other Macs wont read its disks. Tony Diaz goes over that a little bit in the VERY LONG drive maintenance video from Kansasfest 2010 I linked higher up in this thread.

 

[geoffm3]

If you are sure the heads are clean, you could have heads out of alignment, that's pretty easy to check though if you can boot the mac on an external drive you can usually format a disk with out of alignment heads and still read/write to that disk on that drive, just wont read other Macs disks and other Macs wont read its disks. Tony Diaz goes over that a little bit in the VERY LONG drive maintenance video from Kansasfest 2010 I linked higher up in this thread.

Yeah, I figured I'd try formatting a disk in the drive itself and see if I can read/write on it. If that's the case it should be pretty easy to fix.

 

[RoadWarrior]

I took it with me to a vintage computer club I found and they had the correct tools to take it apart. Sadly the heads bent up and they said the drive will have to be replaced. Someone said that they will bring one to fix it so by next month it should be good as new.

 

[RWallmow]

I took it with me to a vintage computer club I found and they had the correct tools to take it apart. Sadly the heads bent up and they said the drive will have to be replaced. Someone said that they will bring one to fix it so by next month it should be good as new.

If you watch the video I linked above from kansasfest, he shows briefly how to carefully bend the head tension spring back into place.

Before that method was found it was always standard fare to have to toss the drive and replace it, but I would try that, really no harm in it, worst case you can't fix the drive and have to replace it, best case you don't need to buy a new drive ;-)