SE FDHD: Now what?

[LaPorta]

Hello everyone,

About a year ago, I restored an SE FDHD from a Maxell blast and was pretty darn happy that I was able to get the thing back to live. It included numerous patches, replacing the SCC, etc. It went so well that it has become my main compact. So, I decided to purchase a MacCon from @olePigeon and was all happy to be able to use ethernet rather than PhoneNet LocalTalk.

I pull the logic board, install the MacCon, and re-insert into the chassis. I fire it up. No chime, garbage on the screen. I figure the MacCon is causing some issue. I remove it: same deal. Eventually I figure out that there is some sort of loose or intermittent connection near the middle/by the main logic board-analog board connector that is causing issues because inserting the connector with downward pressure, even when supported from underneath, seems to cause the issue. Pushing back the other way in the area causes a reset and normal function.

I go and touch up the solder on the board connector pins as I figure maybe one of the pins has poor continuity. As I am doing this, I noticed that the lower floppy port connector might also have a bad solder joint, so I freshen up all of those too.

Well, the connector isn't the direct cause of the problem it doesn't appear. However I flex the board and get it to work and figure ok, I'll get the MacCon going and if it stays as-is in the chassis without issue and works, that's fine. Reinstall it all, fire it up. Machine works ok, boots from its SCSI2SD, all that. Insert Asante driver floppy I made. Floppy access seems slow. I get an error during installation and the disk ejects. So I quit the installer, reinsert the disk. It IMMEDIATELY ejects; doesn't even try to read the disk. Now I'm getting all pissed and worked up, so I pull the board out again and hook it up to my test stand with my test floppy drive. Starts up from my BDC disk no issue. I put the board back. Issue reoccurs. Back to test stand. Now, the floppy drive continuously continues to run the eject motor over and over with no disk. Totally baffled now. I then realize at the test stand that holding down the floppy connector at the board socket stops it from ejecting! There must be some soft of board issue there as well! I checked all pins to make sure they have continuity they are supposed to by the Macintosh Family guide. All seems appropriate, and I cannot find any short between pins from the solder job I did.

Where the heck should I go now? If ever there were gremlins in a board, this is it. What would cause ejection over and over? I was looking for an "eject signal" or "disk in" pin, but nothing that obvious was in the list. It would really be a shame for this thing to be a loss after all the work I put in to even get it to work a year ago. As usual, I'll take any and all suggestions! Not sure if anyone else has SE schematics for this area, but I cannot find any.

Looks like my 128k logic board referbs are on hold now...

 

[LaPorta]

Yes, no matter where I look, no schematics. I suppose the pirated Bomarc ones didn’t have it, either.

 

[LaPorta]

Where’s @Bolle? He is usually good with this sort of thing .

 

[Bolle]

Already read through your post but couldn’t really wrap my head around what might be going on.

Sounds like the board itself might be defective. I have a SE/30 board that behaves similarly. It sometimes works ok, then suddenly stops until I take the board out and flex it. I resoldered pretty much every component on that board already and it’s still doing it.

ROMs are soldered down, RAM sockets are new so it’s not a problem with bad contact on one of those either.

Put it back in the drawer to the other spare boards and stumble over it from time to time when I need a replacement board and accidentally grab this one.

 

[LaPorta]

I appreciate your input, thank you. Perhaps some boards are just semi-kaput. I may try some patches, etc to see what the deal is.

 

[antongale]

Are the SE logic board schematics anywhere on the Internet?  I'm surprised by the lack of data on this particular model.

 

[LaPorta]

I know, that's what I really need. However, there seem to be no complete sets available anywhere.

 

[LaPorta]

Update: I believe that I tracked down the issue with it working in general to a very corroded capacitor and solder joint. No messing around, I just soldered in a new one. It now appears to work well no matter what. However, here is a strange development. I used the board in the test stand, with my known-good test floppy drive. The drive worked just fine, no issues at all, started up. Put the board back in the machine, and I get the same continuous ejecting from it. Not sure what changes from the test stand to the machine itself. Different floppy drives, yes, but the one that is in the machine is the one that it always had inside it. The continuous ejecting also occurred with an attached external drive. That's all the time I have this evening, but tomorrow I will poke around a bit more and try and see how exactly to pinpoint the issue. Is it a complication of the attached drive? I don't know.

 

[chiaki]

[SIZE=1.4rem]is it possible that the corrosion hidden inside the traces add some nasty par[/SIZE]asitic capacitance and other AC-noise  to the DC voltage on the digital signals or powerrails?

especially the floppydrive and controller seems to be very sensitive to this at my repair-experience of my Mac LC with a badly corrosion issue inside the PSU, even after recapping.

(maybe OT but without floppydrive  it works perfect, attached add all strange issues. but if i use a known-good sony PSU none of this occurs.)

my guess the eject happens automatic if the SWIM got a reset-signal(?) or the command and the floppydrive-IC then trigger the eject-motor according to the sony schematic.

but something strange is at the Pin 9 eject-Pin, which isnt connected inside newer macintosh anywhere, but on the older its connected to a ferrit and a cap (like mac II) but my II upgraded FDHD have a cutout in the floppycable?

 

[LaPorta]

I was guessing something of the sort, too, but I think I may be on to something now. Just on a lark, I unplugged the internal floppy and started with an external drive attached. This time, the internal drive worked fine! So I went to sleep, and as I was laying there, it occurred to me that the last time I hooked the external up, the internal was STILL connected! I think that something with the internal drive may have been shorted somehow and the drive circuitry may now be bad. I will have to pull it and test it on my test stand and see.

The adventure continues...

 

[LaPorta]

More testing this evening: hooking a drive to the lower floppy drive port or external Drive port works...only the upper drive port exhibits the never-ending eject cycle issue. Any drive does it, after testing. I cannot seem to find any commonality other than that.

 

[LaPorta]

I think I got it! After more testing, I started reading Pina and came across that reference to old Macs using Pin 9 for a signal that would cause the newer 800k drives to continuously eject because of cables that still had a pin 9 and 20 cable (the SE has no signal normally on pin 9). That explained why when using a yellow-keyed cable, it worked fine. I hooked up my scope, and it turns out there was some sort of phantom interference on pin 9 that was not present on pin 9 of the upper drive slot. I chalked it up to a not-so-good solder job. I sucked out the old and desoldered anew more carefully. It now seems to work well with no issue. I really hope this closes the case on this one.

Here is a pearl for others in the future: interference on pin 9 from an unknown source can cause the issue!

 

[rplacd]

Here is a pearl for others in the future: interference on pin 9 from an unknown source can cause the issue!

I wonder if we should just have a Wiki-fied version of the Dead Mac Scrolls, where we can add our own fixes?

 

[LaPorta]

Someone was advocating for that at one point. I think that would be a wonderful idea.

 

[chiaki]

i like the wiki idea 

Looks like the Ejectsignal on Pin9 is intended to use in a external Unidisk Chassis (with a Button wired to the Ejectpin), that was included in later Version of the Sony 800k Drive and FDHD.

The "macintosh software" Eject seems to be hardwired into the FDD-Controller that trigger the internal EJECT-signal to the transistor (CA1 & CA0 & SEL0 & LSTRB(100ms strobe?)).

Maybe useful if anybody has a faulty drive with eject.

 

[LaPorta]

It started intermittently happening again, so my final solution was simple: desoldering and removing pin 9 from the logic board floppy connector. It does nothing in the SE anyway, so it is not needed.