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Mac SE problems with internal SCSI HD

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weckart

macrumors 603
Original poster
Nov 7, 2004
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I am renovating a discarded SE that had a battery leak among other things. There is substantial corrosion on the cage under the logic board but otherwise, apart from a stuck floppy drive, everything appears to be ok. I have got hold of a replacement logic board, which had a known problem in wanting constantly to initialise the hard drive.

I can confirm this as booting up with a tested working HD from another SE gives a screen overlay error "The disk you have inserted is not readable. Eject or initialise?" Any attempt at ejecting brings the error message back up again. Trying to initialise results in a failure and the error message appears again.

I can boot the SE from an external SCSI Zip drive so I am guessing that this might be a capacitor or power issue. Does anyone with any experience in this have any idea how I can narrow this down?
 
Since you can boot from an external, this is an odd one (and an apparent "SCSI Voodoo" problem).

All I can suggest at this stage is to check that all pins on the internal 50 pin SCSI connector are present and straight. Check that the +5v rail is between 4.90 and 5.1 volts.

Ensure that you're using a known good internal SCSI cable.

If you have a working SE, try the logic board in that chassis with all known good parts (power cable, SCSI cable) - I suspect you've done this already.

You must also ensure that the hard drive connected to the internal port has it's terminators fitted.

LATE EDIT -

Actually, I wonder if this is NOT the hard drive it's complaining about.

A more common problem may be a filter on the floppy drive port.

The clue MAY be here:

weckart said:
...apart from a stuck floppy drive, everything appears to be ok....
Click to expand...

Leave the hard drive disconnected, and see if the board does the same thing.

If it still does it, disconnect any floppy drives (internal & external) and try again)
 
Last edited:
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It appears to be independent of the hard drive. I disconnected both the hard drive and the internal floppy and the error message still appears immediately after booting via external Zip.

IMG_1608.JPG

One other thing, the hard drive makes intermittent grunting noises when powered on, which it didn't in my other working SE.
 
Floppy port Filter is bad. This is an R-C network.

These are a 20 pin component - I'll need to find the part number if you want to get a source.

The alternative is to cut the component's legs and bridge ALL the required pins with resistors.

In the picture below, I've circled the offending parts (yours may NOT be yellow). Without a circuit diagram, I'm guessing the likely candidate is the one labeled "1", but "2" could also be involved.

SE-Floppy Port Filters.jpg
 
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Thanks for this. Would never have worked this out on my own.
 
I was surprised to find the Bourne filters very cheap online here in the UK but the packaging....

IMG_1624.JPG
IMG_1625.jpg
IMG_1626.jpg

Just need to get a decent soldering station now for this. My old irons are useless. Will have to clear the whole lounge to accommodate the parcel no doubt. :confused:
 
Very nice.

The pins on the corners will be the hardest, since they connect to ground and voltage plains.

You may find it easier (depending on the (de)-soldering station you buy) to cut the old ones out at the shoulders of the pins.

Could you conform the part number ?
 
MacTech68 said:
Very nice.

The pins on the corners will be the hardest, since they connect to ground and voltage plains.

You may find it easier (depending on the (de)-soldering station you buy) to cut the old ones out at the shoulders of the pins.

Could you conform the part number ?
Click to expand...
There are four depending upon geography and/or manufacture date. The originals were 115-00002. That I could not find anywhere but the US part number
4120R-601-250/201 came up trumps.
 
So these are the same ones Apple used in the 512K, MacPlus and MacSE and quite a few others.

If anybody has a complete set of schematics for a MacSE motherboard, I'd be interested - all I can find online is missing sheet 2 and 3. :(
 
I replaced the Bourns filters on the right and now the error dialogue does not appear. I can boot from an external floppy drive to desktop. However, I am having issues with the SCSI drive. The internal SCSI drive (20MB) will not mount. I tried getting that and another clean SCSI hard drive to mount with Lido but keep getting an 'Arbitration error' with the SCSI bus. Are the two remaining Bourns filters on the left of the logic board connected to the SCSI bus in any way?

Having Googled this error, it seems that attaching an external SCSI device or terminator might solve the problem but I would rather not have the problem if it is related to the Bourns filters as that can be easily fixed.
 
We might be able to help further with some pics, if that's possible.

What models of drives are they ?

I notice that the name of the boot disk from your earlier post is "MacSE Zip". If that is a zip drive, try disconnecting it (when the mac is powered off), and see if you can boot from an internal HD or floppy disk.

EDIT - Hopfully you have another boot method.
 
The drives are a 20MB Miniscribe. I think this might be dead. It grinds/clunks a few times on boot but never mounts. The other is a Compaq 68pin FastSCSI 2 drive. I have a 68-50 pin adapter on the drive and use a terminated 50 pin cable to the logic board. None of the jumpers on the drive are set, so that it should be drive 0. It also clunks a bit on boot up.

I took the time to finally extract the internal floppy. The original logic board suffered a huge battery/acid leak and corroded a large part of the internal frame. The floppy was filthy and seized up. I spent an hour cleaning it up and it worked first time. These things are pretty robust.

I can get external SCSI Zip to boot so I think the SCSI chains are ok, thankfully. This time around, with the Compaq drive in situ, Lido complains that it cannot ascertain the size of the drive and gives a SCSI bus error as seen below.

IMG_1672.jpg

This was without the Zip drive attached. Lido is running off a floppy with a minimal System 6 folder.
 
What model is the HP/Compaq drive ? (Though I think this one might be toasted).

I'd be looking at the Miniscribe. Which model is it, 8425 ?

Yes, the Miniscribe sound clunky, but it's protocols are better matched to the SE.
 
The Miniscribe is an 8425SA, the Compaq is as depicted here

s-l1600.jpg

and has at least three banks of jumpers to select from. It may just be one of those incompatible drives. Having said that, using another utility Blue Disk Manager it correctly identifies the drive but cannot detect the capacity and gives zeroes for all the other info. It may be a jumper issue or it may be the Mac SE just doesn't have the juice to spin this one up. I have tried with Motor Start Enable on and off. With it on, the disk doesn't spin at boot, so it seems to do the opposite of what it implies (i.e. Enabled means it waits for a signal from the SCSI chain to power up).

In my other working SE, I have another similar 4GB Western Digital with an SCA interface. That one works absolutely fine, although Lido was the only way I could partition and initialise it. None of the patched Apple HD utilities or other apps could do a thing with it.

The only other difference is that the working SE has a soldered original PRAM battery (still working fine!) while this salvaged one just has an empty battery socket.
 
For the Compaq drive, you need the "Force Single Ended" jumper fitted. Also, the "Disable Parity" jumper should be fitted.

What's odd on these drives is the apparent lack of termination on the device. You'll need termination somewhere after the drive. However, if you're lucky, "SCSI Voodoo" may allow it to work without termination. o_O
 
No change after selecting those jumper settings. Still hear the disk trying to spin up then click and spin back down repeatedly. Same error message in Lido. This is what I get frim Blue Disk Manager alongside “Disk Not Ready”

52E8CFDA-00DF-47DE-884D-465BFCD10C21.jpeg

I have active cable termination and for good measure swapped the cable and terminator but with no change.
 
I hope not. I bought it as tested and working. I added it to the SCSI chain in my B/W running MacOS 8.6 alongside a working Seagate drive. It spins up fully after spinning up and down a few times during boot up but FWB HD Toolkit cannot do a thing with it. All the info FWB reports on it has matches that of the Seagate drive except that the Compaq supports 'linked commands', which the Seagate doesn't. Apart from that FWB says that the drive is not ready and may need to be started. Dunno.
 
Nope. Disk not ready means it can only read the firmware but not poll the platters. Unless I can come up with some jiggery-pokery with the jumpers, I am going to have to write this disk off and look for something cheap but not problematical.

I'll steer clear of Compaq and IBM. Another WD SCSI should fit the bill if one comes up on the bay.
 
The only other thing might be mode page settings on the drive, but whether that's the cause (which I doubt) and which ones I wouldn't know.

I do agree that this Compaq drive has some kind of read amp failure or similar fault.

What about the Miniscribe ?
 
The Miniscribe makes a sort of a long hum/beep noise three times then is silent. The HD light flashes on when it tries to seek. I get the same error with Lido that I did with the Compaq "OSErr=5. Bad SCSI command: phase error"

It shows up in the Lido drive listing as a "20MB Hard Disk Drive. Drive Unreadable"
 
Sounds like the Miniscribe thries 3 times to spin up the platters but can't.

Is there a flywheel under the PCB ? If you can give it a nudge with a wooden or plastic stick when it's first powered up, it might slowly get up to speed. Also, if the photo interrupter isn't turning, try turning it 15 degrees when powered off (yes - the one that says "Do Not Turn").

If this works it may stick again once powered down. Whether you can permanently solve the problem is beyond my experience.
 
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