Macintosh SE mounts floppy 3 times

[fehervaria]

I am working on a rescue project of a Mac SE 1/20 (this is the European name of the FDHD). This machine had a hard life - I will write a post about it later (broken CRT neck, broken front bezel, water damage on the metal parts BUT luck: the PRAM battery was popped out early enough to not destroy the Logic Board)
Right now I am facing to a problem what I don't understand:
When I connect an External 800K floppy drive it starts to boot and then mount 3 times the floppy to the desktop.
When I power on the machine the same floppy disk drive's LED turns on and stays on till the machine is on.
If I connect an external SuperDrive to it, it happens similar: machine boots, mounts the disk (only one time) and the ejects immediately. When I "push the disk back to the drive" then it mounts 3 times like with the 800K drives.
The original internal drive is dead (yet). I did not tried another drive over the internal connectors.

Do any of you have any idea what causes this "3 times mounting the disk" issue?

 

[fehervaria]

Could any of you, who knows the SE board well, let me know what components should I check?
Visually everything looks good but I don't know where should I go and what should I check.
I attach a picture about the "floppy area".

 

[Elemenoh]

Have you already tried cleaning the IWM chip and socket with contact cleaner?

Do the drives you connected work okay on another Mac?

Have you tried other disks? Which have you tried with these drives?

 

[fehervaria]

Have you already tried cleaning the IWM chip and socket with contact cleaner?

Do the drives you connected work okay on another Mac?

Have you tried other disks? Which have you tried with these drives?

Three times “yes”:
- I tried with different IWM chip as well, and I cleaned the socket to, each pin-connector one by one;
- yes, the external drives working good with other computers (other identical SE 1/20, SE/30 and Macintosh Pluses);
- I tried different disks, all have the same situation. (800K and 1.44MB disks too).
That’s why I run out of my troubleshooting ideas…
I even tried different ROM ICs.. no change…
The SCSI part of the Logic Board works perfectly, I use a Miniscribe 2485SA as internal disk and a Apple Harddisk 20SC with Seagate disk as external. Both boots up nicely with System 6.0.8 (Miniscribe) or System 7.1 (Seagate).
The Logic Board works with 4x256KB or 2x1MB + 2x256KB or 4x1MB RAM modules… Memory select jumper set correctly, of course.

 

[Elemenoh]

That is super weird. Do all three instances behave the same way? Can you interact with all of them?

It sounds like you’ve already tried different RAM and ROM. Maybe it’s a Video RAM issue?

 

[YMK]

Check the "Get Info" for each of the three mounts. There could be some clues in there.

Are all of the floppy icons solid at once or are some greyed out?

 

[fehervaria]

@YMK and @Elemenoh
One picture tells thousand words:

I can open "any" of it, but can't copy anything onto but copy from the disk.

The Mac thinks it has 3 floppy disk drives and all has floppy inside and each floppy are identical. (In the reality only the external connector has an Apple 800K drive connected...)
That's why I think, there is/are some hardware failure.
I washed the Logic Board today with hot soapy water, cleaned everywhere with IPA... still the same issue. Also cleaned ALL of the pins of the ROMs and the SWIM sockets and the ICs legs as well. Also cleaned the BBU pins... both on the ASIC and the socket too.
Nothing. The Mac still thinks it has 3 floppy connected.

@Kai Robinson do you have the SE LogicBoard schematic? I have the board No10 from the SE ReLoaded black boards, but I still cann't figure out what could be this misterious failure.
The rest of the machine works perfect.

 

[Kai Robinson]

I sure do - here are all 4 pages, but page 1 is the one with the IWM/SWIM and GLU logic. Remember, the GLU is responsible for the switching between the two drives.

 

[fehervaria]

I sure do - here are all 4 pages, but page 1 is the one with the IWM/SWIM and GLU logic. Remember, the GLU is responsible for the switching between the two drives.

Thank you!!! Then I have to dive into.... Isn't the GLU is one of the holy component what we have to "save over" from donor boards? Or is it possible to buy nowadays too?

 

[Kai Robinson]

The GLU was reverse engineered - the .jed can be downloaded and burned to any old GAL16V8

Macintosh-SE-Reloaded/GLU at master · kr239/Macintosh-SE-Reloaded

A 1:1 Recreation of the Macintosh SE logic board. Contribute to kr239/Macintosh-SE-Reloaded development by creating an account on GitHub.

github.com

Also, the functions can be replicated with discrete logic - i even made a mockup with VQFN parts that fits in the same footprint i wanted to test out