Mac Plus floppy ejects immediately

[riversclosehouse]

My Mac Plus (platinum) was running fine until yesterday. It was booting off a minimal 6.0.8 floppy. :b&w:

Now the internal drive immediately ejects the disk.

I did two things

1) I attached a non-tested A9M0106 Apple 3.5" external drive

2) I inserted an ancient 800k disk into the INTERNAL drive. (looks good on inspection)

The internal drive is now making a "swooshing" sound, which it never did before. :-/

http://youtu.be/suPO60OnS4Y

When I insert my system disk now it takes it in, makes a swooshing sound as it's attempting to read it and then ejects it immediately. It does the same with a Beyond Dark Castle game disk which it was previously able to read. :disapprove:

Do you think I need to clean the heads, or do I need a refurbished drive ? Or did the controller board blow when the old external drive was attached ?

Any thoughts are appreciated. It's very disappointing.

 

[jdmoser]

Do you think I need to clean the heads

I can't speak from experience, I'm a few months new to restoring compact Macs... but cleaning the drive would absolutely be my first thought if I were in your place. There's instructions here on how to re-lubricate a floppy drive... I don't know if additional cleaning instructions are necessary/exist, but this forum is crawling with that sort of information

I've considered cleaning the floppy drives in my Plus and SE/30, but they're working pretty fine as is so I haven't bothered yet.

Sorry if I'm no help, hehe, but as I said... cleaning the drive would be my first guess, and failing that, finding a replacement drive.

 

[nvdeynde]

I did two things
1) I attached a non-tested A9M0106 Apple 3.5" external drive

2) I inserted an ancient 800k disk into the INTERNAL drive. (looks good on inspection)

Does the Mac boot from the external FDD A9M0106 with the same disc or other known good bootable discs ?

If not, slide the metal cover of the floppy disc away and look with a magnifying glass to the surface while gently rotating it: do you see any scratches, even minor one's ?

It is possible that the external FDD was faulty and damaged the FDD controller or the Bourns filter.

You can also try swapping the drives and see what this gives. The drive in the external enclosure should be the same as in your Mac Plus.

My first shot would be cleaning the heads of the internal floppy drive with isopropyl alcohol and see what this gives.

I listened to the youtube video but the sound is very silent: it looks like the heads don't attempt to read the disc at all.

 

[RickNel]

It is possible that the external FDD was faulty and damaged the FDD controller or the Bourns filter.

From recent experience, my bet would be the Bourns filter. The external floppy port has power pins on it, and if those get fed back onto a signal pin they will blow one or more channels in the filter. It can happen from a fault in the drive, but also wrong cable pinouts - say the drive was configured for a different model Mac. Those external ports are treacherous, because they serve different functions on different models, but they look the same. You need to check compatibility before firing up an untested (says the one who didn't do that, last time...)

Fortunately, the Bourns filter usually acts as a fuse and protects the IWM/SWIM controller chip. The controllers are much harder to replace.

Rick

 

[nvdeynde]

A9M0106 Apple 3.5

The external drive he used is a Unidisk model suitable for Apple II series and Macintosh. The difference between the external 800K drive for Macs only is that the Unidisk model has an extra PCB between the cable and the floppy drive. It could be that the FDD inside the enclosure or the PCB is faulty.

One could open the enclosure to inspect it and better try it without the internal PCB: so plug external FDD cable directly in the floppy drive instead of running it through the PCB.

Anyway, like I wrote before, it's probably the Bourns filter or SWIM controller if you can't get the internal drive to work anymore.

Test the Bourns filter for, continuity: it should read around 24 to 25 Ohms exept for the ground pins and both side of the chip: these read zero of course.

The Bourns you need to test is just above the FDD connector on the logic board.

Keep us posted.

 

[riversclosehouse]

Thank you for your detailed replies, and for looking at the youtube video.

It is as I feared: cleaning the internal drive had no effect whatsoever. It still spits out the disk which worked fine for months before.

I can only hope it's that Bourns element and not the Sander-Wozniak Integrated Machine (SWIM).

Right now I know more about the Bourne Legacy than soldering on a motherboard, but that is about to change.

Check back in a few weeks when I've acquired the skills and tools and I'll give you an update. Or look for a smoldering hole in the ground in north-eastern Ontario.

If anyone feels so inclined to point to a basic kit list of what I need to change this filter... much obliged. The Torx screwdriver I have

Thanks again!

 

[nvdeynde]

First check if the Bourns filter is bad before attempting to replace it.

 

[RickNel]

The first thing you need, if you don't already have it, is a good digital multi-meter with continuity, resistance and voltage ranges. Herz and capacitance ranges can also be handy. Without that, you have no way of checking components.

Read up some threads on de-soldering. There are many tricks to make the task safer and easier and many guides available online.

Rick