I also have a Mac II but the drive carrier/sled are different to yours - mine is the same as the ones in the IIx and IIfx designed for an ordinary 3.5" Quantum.
Yours appears to be an earlier version made for a larger drive.
Does the CPU heatsink get hot while the machine is on? Some 601s suffer from cracking or shorted pins.
Depending on the answer to the above, if this machine isn't recapped yet, I wouldn't diagnose/troubleshoot further until you've recapped it. The 7100 is from 1994/1995 - so those caps are...
I wouldn't bother working on that power supply, it clearly has multiple components that are dead or nearing death and these are not very good power supplies even when they work.
Drive is most likely toast, yep. But it will be worth trying some other formatters, Lido has been mentioned but there's also FormatterOne Pro and Silverlining.
Thankfully, there are various options to replace it with something that's more reliable - the easiest options are either BlueSCSI or...
The 475 can run with a full 040 which includes the integrated FPU, you just swap the low-cost 040 processor out for a full one - it's a socketed CPU. You can also get a 475 running at 33MHz with a similar resistor mod.
Apple was funny about configs back then and wouldn't sell a 33MHz machine if...
@zezba9000 Nice LC III, but you can move R14 on the top of the board to R74 on the back. That will boost you from 25MHz to 33MHz, effectively making your LC III into an LC III+
And then buy an LC 475, that is even faster still because the 68040 was a huge leap from the 68030. :D
Did you hook anything up for that or not? ATX PSUs don't support soft power, you need to add your own little circuit for this.
Something like this
Also see here: https://bylenga.ddns.net/index.php?page=Centris_ATX.php
(from that page) - basically same as the above but drawn a little...
LC II hardware reference notes: https://cdn.preterhuman.net/texts/computing/apple_hardware_devnotes/Mac%20LC%20II.pdf
Measuring PSU voltages is just a case of using your multi-meter to measure the voltages at the pins on the power cable on the logic board side.
The LC power pinout is here...
@DrewyNucci Sorry, I edited my post while you were replying. So the other thing is that the SE/30 board cannot be fitted to the Classic, the chassis/case are different.
SE/30 boards very rarely come up on their own and when they do they are expensive, it is easier to find a complete SE/30 to...
Welcome to the forum.
Unfortuntely it's not this simple. The SE/30 board won't work in the Classic chassis/case - the power supply/analog board are different and cannot be swapped between the two.
The reverse engineered boards are really for those who have a donor SE/30 board and SE/30 to use...
What sort of capacitors are on this board, electrolytics? The original I assume, not replaced?
You can have bad traces without it being visible. You can also have electrolytic fluid leakage without it being immediately visible, as it can pool underneath the caps. Have you checked continuity yet?
Myst was originally developed on an SE/30, IIRC they later used Qudras when they came out for rendering but I think I recall in an interview one of the creators mentioning the original development was done on an SE/30 with a colour card.
Nope, just means it can take a tiiny bit more load, I can't really think why Apple would've specified that the 2nd revision was uprighted slightly. The difference between the two isn't the pin out, it's just that the 2nd one is a later revision, so it will work fine.