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  1. What would be really useful is to rule out a bad CPU or RAM (more likely on-board RAM). My guess is those crap PSU's that came with these caused some kind of stress somewhere. Another observation is my motherboard that does work has a non-working SCSI. Even re-cap didn't fix that. You also notice how the SCSI drives on these were powered through the board? I wonder if a power stress issue exists in that area. Maybe some kind of power short. Because there are so many people with the same sounding issue figures crossed it a fixable issue. My first/next suggestion would be for someone to replace the on-board memory. My board that doesn't work didn't have the best looking modules. Also when there is a bad PSU for long periods of time... ram can get damaged (pretty common I think). Memory on the board is "TI TMS44C256DJ" which can be bought here: https://www.ebay.com/itm/TI-TMS44C256DJ-Dynamic-RAM-Fast-Page-256Kx4-26-Pin-SOJ-New-Quantity-5/251812621170?epid=1863064326&hash=item3aa133ab72:g:0AkAAOSw-W5Uym1J If anyone has a bad board with some better soldering equipment for this kind of job you should give it a shot. I'll buy the ram but this requires a better soldering skill and equipment than I have.
  2. I already recapped it.
  3. Update. I ended up having issues with PICO PSU's even a 300w one. Maybe the caps don't hold enough juice but only my 500w standard ATX PSU keeps the computer 100% stable all the time. Even a 250w 80 PLUS Bronze Certified ITX PSU has stability issues after a while: https://www.amazon.com/gp/product/B006ORBC14 Sadly I will have to keep the 500w PSU external from my computer. Maybe someone has a good idea of why only the 500w psu is the only one that works well? EDIT: After more testing even the 500w the computer will eventually crash running a screen saver. O well at least its stable enough for what I need it for.
  4. Also here is a picture of the heatsink I used on the CPU. Just some extra love.
  5. A long overdue update. My bad motherboard still has the bad chime sound after replacing its 40mhz crystal oscillator. My good motherboard (besides the SCSI not working [so it boots from the Mac ROM-inator II]) I replaced with a PICO PSU I shoved in the original PSU metal box. So now its powered with a 90W / 12v laptop power supply. Custom ROM SIMM used: https://www.bigmessowires.com/mac-rom-inator-ii/ I bought this 20pin one but any 24pin one should work as well: https://www.amazon.com/gp/product/B07H5FP5KY/ A power brick like this works with it: https://www.amazon.com/gp/product/B076C7X7GW/ Because my old mac tube screen is going out I got a "HD15 VGA Monitor Female to DB15 MAC Male Converter Adapter". You can buy those here: https://www.ebay.com/itm/HD15-VGA-Monitor-Female-to-DB15-MAC-Male-Converter-Adapter-w-Dip-Switches/271137033572 For Macintosh IISI you only need switch 6 and 8 on. Switch reference download link: https://1drv.ms/b/s!Alt5wRhQYKD7geVqezziWWeKRZ5-hg
  6. Or you can just make a custom new PICO based PSU replacement: Scroll down on page 3.
  7. Here is the stuff I used. The solder core with that rosin work way way better than what came with the solder iron. Before you apply the rosin, dab some 99% Isopropyl Alcohol to clean off the area, then dab some rosin paste on the area and apply some solder before setting the cap. Also make sure to use the super fine point tip on the solder iron. Solder Iron: https://www.amazon.com/gp/product/B014KBIB Rosin Paste Flux: https://www.amazon.com/gp/product/B008ZIV85A Rosin Core Solder: https://www.amazon.com/gp/product/B00030AP48
  8. #1 I ruled out buy connecting the caps from the working board to the non-working one with some wire clamps. The CPU being as hot as it is is going to be fine when idle. Under load for a long period of time it may not be (as is the case with ARM chips in your phone etc). My concern is these computers have been around for a very long time and the one I got that doesn't work was very dusty which can increase the CPU temperature even more and if someone left it on under stress for a long time it could cause damage as these old computers don't have auto power off when the CPU gets to hot (if you get yours working again, I would put a heat-sink on it). When a CPU goes bad it can still partially work but then fail when it starts to use other parts as not all circuits will just stop functioning. The other possibility is the original PSUs in these damage something else on the motherboard. Both PSUs in the working and non-working IISI computers were leaking some fluid on the board and both PSUs had issues. If the original PSUs were this bad, maybe a bad CAP in them caused a bad power fluctuation on the motherboard and damaged a chip when going out. My hope is it damaged the CPUs crystal oscillator and the reason I think I could be on the right track is the CPU in the bad computer gets much hotter much faster than my working one. I'm moving soon, so my on and off tests with this may slow for a month or couple of weeks. Just FYI.
  9. Also just a tip. If you need to convert an ATX 20-pin to a 10-pin you can also just use a PICO PSU to embed the PSU directly into the Macintosh computer as they're super small. Something like this would work: https://www.ebay.com/itm/12V-180W-DC-Pico-ATX-switch-PSU-with-Power-Adapter-Car-Auto-MINI-ITX-Power/263087650726 For a CPU heat-sink, get the same ones used for ARM A20 (they're the perfect size [tested]): https://www.ebay.com/itm/Heatsink-for-Cubieboard1-Allwinner-A10-Cubietruck-Cubieboard2-A20-heat-sink/231904141192
  10. Did a quick clean of the new motherboard. Everything works except for the scsi. I know the hard drive and cable are fine as it came from a working computer. Might need to replace the caps if thats the issue.
  11. Made some directions for making a Macintosh IISI PSU very quickly. Based on a YouTube video but simplified. 1) First buy one of these "24 Pin to 10 Pin" off Amazon or Ebay: https://www.amazon.com/gp/product/B07C5P5H2L 2) Rewire it with the image below. More info and reference files: https://1drv.ms/u/s!Alt5wRhQYKD7gd4qoWijVukp9uDeOg YouTube video this is based on: https://www.youtube.com/watch?v=CNerj2mQ4vw
  12. Ok just got another Macintosh IISI motherboard. It works perfect with my custom ATX PSU! Still need to wash the motherboard but its sound is still strong so caps seem still ok. The custom ROM SIMM doesn't solve the problem on my old board (so ROM SIMMs are not the issue). But now I can compare some stuff. The new one has all black memory slots and doesn't require a SIMM. The old one requires a SIMM with all white ram slots. So first thing I noticed and was looking for was CPU temperature. Why? Well both ROM SIMMs chime sounds load (stock and custom) but then the board just hults. Disk drive doesn't register or anything else on the board. This makes me think a couple things (which I will try as time goes on). #1) The large dark blue caps close the the floppy disk drive might be bad which could be causing something else to fail on the board. #2) The CPU get very hot on these... to hot for my liking. Normally CPUs that get this hot usually need a heat-sync when under heavy use. (comparing to RaspberryPi etc type systems). The CPUs might be burning out (So I will put a heat-sync on my working board). Pretty sure all my other macs without heat-syncs don't get hot at all. #3) My bad boards CPU gets hot much faster than the working CPU. Its possible the crystal oscillator that controls the CPU clock may go bad on these computers... and the oscillator after a time could be its under some kind of temperature stress from the CPU not being cooled properly. IDK if 1-3 are valid ideas yet but will try to knock out and validate some of them. Images below show off the new working one and old broken one.
  13. Still waiting on other motherboard (which has black memory slots). Just got the custom ROM SIMM in the mail today so haven't tested yet. Will report back once I do.
  14. That would be nice if there is a General category form area? Create and link it.
  15. One other note. Waiting for mail. Got a custom ROM SIMM from BigOMessOfWires to see if a custom rom skips some error the stock one is having. Also got another motherboard from Ebay that doesn't need a ROM SIMM to see if I can get that one working.