Acquired my Mac SE/30 and cleaned the logic board thoroughly. Removed the battery and attempted a boot. The once not working machine booted right up off of its 40MB SCSI drive. I also acquired an external Super Drive and could boot successfully using a System 7 Disk Utility disk. I dared not to use the internal drive as it showed signs of being filled with dust bunnies.
I recapped the board using Tantalum capacitors rated for 16v but now I am finding posts that warn you should up the voltage limits to 25v for these capacitors, so may have to redo the recap. Upon booting after just changing C1, C3, C4, C5, C6, C7, C8, C9, C10, C12 and C13 I find that I can boot and hear sound but now the disk image is showing an 'X' instead of the usual '?'. I think nothing of this and continue the recap by replacing the two axial capacitors at C2 and C11 and this is where things get more complicated.
Upon booting I am greeted with a blank screen and no sound. I eventually learned of a technique to run the logic board outside of it's chassis using a benchtop power supply connecting 20v to the positive side of C2 and 5v to the positive side of C11. No bong, but I am seeing power throughout the board. I learn more about the Motorola 68030 chip and find that it is supposed to "walk the ROM". So I pull the ROM chip and probe several pins and voltages are static. This is when I determined that the system was getting a low "reset" signal on all ICs. After staring at schematics and probing, I finally find that I have inadvertently grounded a trace that goes very close to C2's negative leg. This trace was responsible for sending low reset signals to the GLUE chip.
After repairing this trace, I am still greeted with a black screen and no bong. I learn that the Sony Sound chips are basically responsible for sending reset signals to the entire board. I trace the low "reset" signal back to these chips. They were showing up as unpowered. Somehow these chips were not getting 5v, so I bodged in a connection to C2 and finally hear the bong! After putting the system back together the disk image "X" would later come back to haunt me. I booted from the SCSI drive only to be greeted with a a repeated disk unreadable loop first pointing to the internal disk drive then to the external disk drive. Removing those drives from the system does not resolve the issue. If I boot without the SCSI drive hooked up, I just get greeted by a Disk that contains and 'X' instead of a '?'.
My attention has turned to both the bourns chip along the external disk port path and the SWIM chip which is responsible for selecting a disk drive and querying it. Sadly I do not have an extra SWIM chip or donor board at this time. The bourns filter chip is showing 50 ohms across all pins except ground which is in-line with what I know of this chip and how it works. I am looking for any other methods to test this chip. Additionally when checking continuity against the 5v power lines to the SWIM chip I am finding shorts to ground at ~77 ohms. I do not know if this is expected though, the missing page 9 of the Mac SE schematics may have more details that could help me determine if this is normal. I will note that when the system is powered the SWIM chip power pins are showing 5v so sadly I think this doesn't explain the issue I am seeing with this chip.
I have now methodically traced all 'a' and 'd' bus lines through to the CPU and ROM. All of those traces look good so the issue is not with those bus lines. I have sourced a SWIM chip as well as another chip, if that source comes through and I receive what I ordered, I will post the source for others. When booted, the SWIM chip never brings up HDSEL and just alternates ENABLE on both 1 and 2 channels. My hunch is that I have somehow damaged this chip or it was on its last legs when I hooked up the external drive. Unfortunately what I know of this chip is it is quite integral to the system so I can't just remove it and test, I need a replacement.
Either way I will know if this was the right or wrong call when I have a replacement to test. While I waited on the replacement I went ahead and pulled the Bourns Filter. The Bourns Filter seems fine when it is out of the logic board based on this video which has a very good explanation of how this chip works and how to test it, there is no short to ground from the filter pins. I do see shorts to ground on the SWIM chip side which has convinced me that this problem definitely lies closer to the SWIM chip.
I got a new SWIM chip fairly quickly but decided to go ahead and pull the Bourns Filter so that I could test it more thoroughly and found that the chip actually did have a short to ground on one of the lines. However after pulling the filter, I was still seeing a really bad sign. The ohms resistance across the 5v line was ~95 ohms which seemed off. I decided to put the board back into the system without a filter chip to see if the behavior still occurred and it didn't. I was seeing the blinking '?' disk image. Finally, no X, however none of my floppy disk drives were working. I really felt that putting a new filter wouldn't resolve this but went ahead and ordered some used filter chips. However I didn't want to tempt fate and decided to wait until I had all new SWIM and filter chips before changing out the SWIM chip. The reason I decided to do this was because I had a somewhat working system. I could at least use it with SCSI devices. Finally I received the filter chips and decided to just replace that one chip and see if it made a difference. After installing a new, working and tested filter chip, the system would still boot but no activity on the floppy drives. Neither external or internal.
Replacing the surface mounted SWIM chip wasn't that difficult. I used Kapton tape to protect all of the plastic components and used a hot air rework station to remove the chip. It came off fairly easily. I wanted to install a socket for this position on the board. That didn't go well at all. I just don't have a lot of experience with soldering sockets yet and basically destroyed the socket by melting it and somehow ripped a pad up. This wasn't working, so I removed the socket which took 3 more pads with it. Fortunately the 3 pads were not connected to anything and I needed to bodge pin 27 to a via that was under the chip. I ran a small wire from the via leaving lots of excess and soldered the chip to the board including the wire from the outside of the chip. I then used an Exacto knife to cut the excess wire hiding the bodge under the chip. After replacing the SWIM chip, I booted the machine which thankfully still chimed and put a floppy in the disk drive which I had cleaned and lubricated while I was waiting on the filter chip. Success! The disk worked like a charm. I tested with an externally connected disk drive and it worked as well. This Mac SE/30 is now completely restored! In case it helps someone who might be diagnosing a problematic chip, the ohms reading on the 5v rail is now ~400 ohms far better than what it was. So if your Mac is considerably lower than that you probably have a malfunctioning chip.
I grabbed lots of photos of each part that was dismantled and reassembled and cleaned while working on this system. I went about meticulously cleaning out all of the dust and debris that had built up on the Analog board, chassis and CRT tube. I also disassembled, cleaned and reassembled the mouse and keyboard. This machine looks like new. I will post photos and a description of everything I did to clean the rest of the machine soon.
More soon.