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New IIsi project - any tips?

JC8080

Well-known member
I recently picked up a IIsi as a project, all my other machines are earlier compact Macs, this is my first Mac II project. Before I dive into it I thought I'd ask if there are any things I should know about working on these machines.

The seller said when he turned the machine on the power LED lights up, but no other signs of life. He purchased a Plus and the IIsi came with it, he wasn't planning on keeping it so he didn't do any further troubleshooting. The battery did not leak, however all the caps have leaked, so I will be doing a full recap. I assume this is the cause of the machine not powering up. My plan is to clean the board up and look for any damaged traces from the leaking caps, and go from there. Is it common for leaking caps in these machines to damage the board? Between the cap goo and the dust stuck to it, it's really hard to see if there is any damage until I clean the board. The battery has been removed after I took the attached photo, I didn't want that ticking timebomb anywhere near it. Any general thoughts/tips as I start this project?

I currently don't have a monitor for the machine, I'm going to start looking locally, I'd rather not risk having one shipped. If I get the machine recapped before I get a monitor, should I be able to power it up and see signs of life, assuming the recap fixed it? Should I be able to hear a chime? I know I wouldn't be able to do any real troubleshooting until I get a monitor, it would just be nice to tell if my recap was successful, even if I don't have a monitor yet.

Thanks!
 

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bibilit

Well-known member
The board and the PSU should have new caps, PSU is a bit tricky as is a soft power unit.

You can deal with a video converter and a LCD instead of the original CRT.

What is the pink part ?
 

3lectr1cPPC

Well-known member
+1 on the PSU. They’re awful. You will almost certainly have leaky through-hole and surface mount caps inside of it. Good luck.
 

JC8080

Well-known member
Oh very cool, I knew the 25mhz overclock mod was a thing and wanted to do that once I get it working, I hadn't looked closely enough to see someone already did it. The machine also has a NuBus adapter w/ FPU and an Apple 8*24 video card. The guy I bought it from said it had 4mb of RAM, but I just pulled a SIMM and it looks like a 4mb SIMM to me, so that would be 16mb total, though I couldn't find great info online.

The recapping will make a good fall/winter hibernation project, now that the nice PNW weather is gone. ☔
 

imactheknife

Well-known member
Sweet little machine! Got a Ethernet card in my se/30 with fpu socket so i pulled that and put in my iisi. Will get different card for se/30
 

Byte Knight

Well-known member
I currently don't have a monitor for the machine, I'm going to start looking locally, I'd rather not risk having one shipped. If I get the machine recapped before I get a monitor, should I be able to power it up and see signs of life, assuming the recap fixed it? Should I be able to hear a chime? I know I wouldn't be able to do any real troubleshooting until I get a monitor, it would just be nice to tell if my recap was successful, even if I don't have a monitor yet.
Yes, it should chime and the HD and disk drive should spin up, unless you have a break in the 12V rail like I did. You might check out my recent IIsi restoration here:
 

imactheknife

Well-known member
The power supply will be the fun one. Recapped logic board straight forward unless you have trace damage etc. the psu is nasty on these as you might find out. I recapped mine, it worked for a bit and died. So i bought a recapped online.
 

JC8080

Well-known member
Yes, it should chime and the HD and disk drive should spin up, unless you have a break in the 12V rail like I did. You might check out my recent IIsi restoration here:
Thanks, I'll check that out.
The power supply will be the fun one. Recapped logic board straight forward unless you have trace damage etc. the psu is nasty on these as you might find out. I recapped mine, it worked for a bit and died. So i bought a recapped online.
Thanks for the heads up, I'll check out Branchus Creations video on the IIsi PSU recap and see what I'm getting myself into.
 

JC8080

Well-known member
I did a thorough clean of the logic board with an alcohol bath and some scrubbing, it came out looking great. Based on a naked-eye assessment, I don't see any damaged traces, even around there the cap leakage was worst. 🤞

Things weren't so great on the back. Everything looked fine, except for the overclock oscillator someone with no skill installed previously. There was some corrosion around the solder joints, so I took a q-tip and some alcohol to clean it up, and wasn't pleased by what I saw. I'll let the photos speak for themselves. Maybe they used corrosive flux and didn't clean it afterwards? I grabbed my meter and the Bomarc schematic, and all the legs have continuity through to their destination, so I might have dodged disaster. I'm definitely afraid to try to re-flow those joints, I think it's probably better to leave them alone as long as they are working.
 

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rikerjoe

Active member
I just finished a successful IIsi restoration. Fun and challenging project! Here are a few tidbits from my experience. Definitely, my Sony PSU needed recapping - it barfed its brown cap goo all over one side of the logic board and on the bottom case and all over itself, including the underside. Nasty! All cleaned up nicely with IPA for the logic board and PSU, and a good soaking in soapy water for the case. Recapping the PSU isn’t too terrible if you’ve done a through-hole recap or two and follow the PSU recap video by Branchus Creations. I removed a few of the other components in the PSU to clean the cap goo thoroughly. The daughter board in the PSU is crap and easily loses pads (ask how I know). The logic board recap isn’t a big deal - all SMD caps are the same and the two axial caps are the same. Check continuity on the +12V and -12V rails (I checked via the external floppy port). In my case, the PSU cap goo wicked through the connector and ate at the traces to the +12V (pin 1) and -12V (pin 8) rails, which required repair after removal of the connector from the logic board. Good luck!
 

JC8080

Well-known member
I picked this project up again, my other IIsi board has been relegated to either a future project, or parts.

@rikerjoe, I checked continuity on all the PSU connectors including +12V and -12V, following the PSU connector to UK3.

Here is where the board currently stands:

The PSU is recapped and known-good. All the voltage readings are good. The PSU will turn on via the PSU button or the ADB button. On power-up the green LED turns on, there is a pop out of the speaker, and the display shows solid purple - no further activity. No chime through the speaker or headphones.

Things I have done:
  • Re-capped logic board
    • Soaked the board in IPA to clean before the recap
    • Thoroughly cleaned cap goo with IPA after removing the caps
    • I haven't cleaned the flux yet as well as I should have, so that is what you are seeing in the photo around the caps, not cap goo
  • Checked CPU reset line (starts low, goes high)
  • Checked CPU clock signal (shows 25mhz, the machine was previously overclocked with a 50mhz crystal)
  • Checked for loose pins on all ALS245s
  • Checked for loose pins on the corner of the CPU closest to the cap (the heat-sink previously installed makes it difficult to access all CPU pins)
  • Checked continuity on all pins of the PSU connector, per @rikerjoe's suggestion above.
Does anyone have any ideas where to go next? When I did the recap I checked for broken traces under the caps, but I am thinking maybe I should remove the caps and 2x check.

PXL_20230826_175312041~2.jpgPXL_20230826_175306857.jpgPXL_20230826_175258992.jpg
 

David Cook

Well-known member
Check for chip enable on the ROM chips. There is crud around W1?
Check for bad traces around C34. Not only the nearby transistors/diodes, but also the CPU pins around 50/51.
 

imactheknife

Well-known member
Do you have an air work station? The chips in the attached picture almost always have to come off in my iisi experiences, which is many! The cap juice can affect the legs attachment to the pads, and even legs look solid but turn to dust when touched. I just operated on a egret chip on classic ii board that legs turned to powder
 

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JC8080

Well-known member
Check for chip enable on the ROM chips. There is crud around W1?
Check for bad traces around C34. Not only the nearby transistors/diodes, but also the CPU pins around 50/51.
Thanks, I'll look into the ROM chip enable and inspect the other items.
 

JC8080

Well-known member
Do you have an air work station? The chips in the attached picture almost always have to come off in my iisi experiences, which is many! The cap juice can affect the legs attachment to the pads, and even legs look solid but turn to dust when touched. I just operated on a egret chip on classic ii board that legs turned to powder
Thanks, yes I do. It's not too much trouble to remove, clean, and re-install. I checked all the legs on the ALS 245s with a pick and they seemed solid, but cap goo can do some weird stuff.
 

imactheknife

Well-known member
Thanks, yes I do. It's not too much trouble to remove, clean, and re-install. I checked all the legs on the ALS 245s with a pick and they seemed solid, but cap goo can do some weird stuff.
On almost every classic ii board i have had to remove egret, sound, and a few voltage regulators because of cap juice. Even though legs looked ok. Hot air stations are the best. Once comfortable using one, they are awesome for removing / installing stuff

I also use wick / flux and scrub pads and apply new solder.
 

JC8080

Well-known member
On almost every classic ii board i have had to remove egret, sound, and a few voltage regulators because of cap juice. Even though legs looked ok. Hot air stations are the best. Once comfortable using one, they are awesome for removing / installing stuff

I also use wick / flux and scrub pads and apply new solder.
I put off buying a hot air station for quite a while, I'm glad I finally did. I bought a cheap-o one off Amazon and it works great. I also bought some ChipQuik for removing larger ICs, it works great, I used it to remove the CPU from my other IIsi board.
 
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