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System 7.0.8 reports the disk as unreadable and asks if you want to initialise it. Disk First Aid says "Bad Disk Name".

After finally getting around to looking at my second SE/30 and its SCSI problem I think I need a second opinion: The machine is fully recapped and other than the SCSI issue works perfectly. Symptoms: SCSI disks are seen but any filesystem found on the device gives an error "Invalid name"...

Yes, CMOS is less power hungry, but it also has a lower voltage for logic high and has a lower maximum current throughput. CMOS driving TTL/NMOS chips can cause them damage due to excessive power draw. Also the TTL chip can sometimes not see the logic '1' values. There are special CMOS chip...

Could the desktop ones be NMOS and the laptop ones CMOS?

Someone sells a Mac Portable SCSI to normal SCSI+Power adapter board+cable on eBay. Be careful though, the one I got had the Molex power connector incorrectly wired, with the +12V and +5V wires reversed, which killed two hard disks and an SCSI2SD card before I realised what was happening...

Well, WD-40 (or, Water Dispersant No. 40) is a reducing agent, designed to remove oxidation so as to allow engines to start after the high tension side became damp, so it makes sense that it would reduce the oxidation caused by the leakage, possibly redepositing copper.

They will work with any switch, but only at 10Mbit. It merely depends upon how brain dead your network switch is. If it's a decent one then without being able to negotiate the connection it should default to 10Mbit, which is what the old 10BaseT hubs ran at. I had my SE/30 connected to a...

You'd need a Mac with an ethernet interface running 7.5 to act as a bridge. I used an SE/30.

DO NOT EVER POWER WITH ONLY THE CHARGER! (a) The charger can't produce enough power. (b) Without the battery the power subsystem is unstable and generate high voltages on the +5V line, frying chips. The power sub-system is not failsafe. Only ever start the machine using a properly charged...

This should do according to the schematic   Mouser No: 844-IRF9Z30PBF Mfr. No: IRF9Z30PBF Mfr.: Vishay Semiconductors   You can see the designation on Q14 and Q15 in the picture posted above.

I'm guessing that you are in the USA, in which case Mouser should have them.

I'm afraid not. Without starting to remove chips one by one, which is dangerous in of itself, until I find the one pulling the line up there's not much more I can do. Given that the machine is not going to be powered up and sleeping much (it's going to be mostly packed away with all batteries...

Also, trying to run with a bad battery is a potential disaster for the Portable as the power sub-system doesn't fail safe and can send high voltage down the +5V line killing chips.

Q16 does control the +5V line, as can be seen in the circuit schematic that techknight posted above. Looks like at some point there might have been a short circuit on the machine and it overheated the component. The IR9230 components are cheap and relatively easy to remove with a hot air...

Sounds like something with a lot of electronics experience, both analogue and digital, might have to work on then.

Electronically, what does it actually do?

Those voltages are definitely low relative to my machine. Do they change when you try to wake the machine up?

For the 5V you can clip the negative probe from your voltmeter to any GND point and then put your positive probe on pin 3 of MOSFET Q4 (at the top right as you look from the front of the PCB. This is always on so should show +5V even if the machine is shut down. Keep monitoring the voltage as...

Yeah, it's a non-backlit. From what I remember those are a set of three 244s. 244 buffer chips are notorious for going faulty.

I've also seen many 74xx244 chips go bad in strange ways, including sending stuff down the inputs.