Uploaded October 2025 | Updated September 2026, 1 week ago
The Macintosh IIsi was launched as a lower-cost alternative in the Macintosh II series. To keep costs down, Apple used more electrolytic capacitors, and the surface-mount electrolytic capacitors from the early 90s are past their expected lifetime. In addition, despite the power supply being made by Sony, the capacitors in it are also known to leak (though I can't help think "cost tweaking" by Apple led Sony to use lower grade capacitors).
Last time we looked at the IIsi that would chime and then death chime, I found two broken traces and ran some bodge wires... only to have more data bit errors, not fewer. IIsigh. Before I start major drastic chip replacements on a now fragile PCB, let's take one last look at what Diagnostic Mode is telling us. Because I might have made a mistake running those bodge wires.
And if we get the IIsigh booting, we will finally full-send that promised 25MHz upgrade attempt.
Will Diagnostic Mode lead us to the error? Will the chat come in clutch (of course)? Will we see why the IIsi was so crummy after installing the 50MHz oscillator? You'll have to watch to find out!
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Table of Contents
0:00:00 Pre-Roll
0:02:39 Greetings and Announcements
0:11:15 Wheel of Regrets™ (Who comes up with these titles anyway?)
0:11:38 Wheel of Regrets™: Western Digital WD1003V-SR1 Winchester (MFM) Disk Controller
0:16:25 Picking Up Where We Stopped Last Time with IIsi Number 4
0:45:36 Bodge Wires, Two Little Bodge Wires, Two Blue Bodge Wires, Where Are You [Going]?
0:48:27 Troubleshooting a Ko-Fi Notification Issue
0:52:09 I Finally Inspect the Board with a Multimeter
0:59:30 Oops, My Bad... IIsigh
1:03:00 Removing the Bodge Wires and Retesting
1:07:00 Troubleshooting a Discord Issue (by ending the task)
1:09:00 Continued Retesting and Chatting About Streaming
1:17:06 Talking About the Work Bench
1:29:10 Double-Checking Traces and Correcting the Bodge
1:38:37 Smoke Testing ("We've Got Progress Here Folks")
1:47:15 Five Little Megabytes of RAM, Ah, Ah, Ah! (Thunderclap)
1:52:28 BlueSCSIs Don't Work on the IIsi Unless You Got Power
1:58:00 Snooper 2.0 for a Few Cycles More...
2:11:44 Speedometer Baseline Benchmark
2:20:00 Baseline Benchmark Re-Do (without OBS Overlays)
2:29:30 Removing the Serial Cable and Replacing the System Bus Oscillator
2:48:10 Post Upgrade Speedometer Benchmark
2:57:00 Closing Thoughts
3:08:05 Outro
*
Ways to Support the Channel:
☕️ Tips or Support via Ko-fi: ko-fi.com/jdmcs
🈷️ Support me on Patreon: patreon.com/jdmcs
📦 Amazon Wishlist: jdmcs.net/wishlist
... or simply do the YouTube things: Like/Dislike, Comment, Subscribe, Enable Notifications, and participate in the Chat. These things help the channel, too!
**
Read Computerized Start™, my Official Blog: jdmcs.net/myblog
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Follow me on Twitter: jdmcs.net/mytwitter
The Macintosh IIsi was launched as a lower-cost alternative in the Macintosh II series. To keep costs down, Apple used more electrolytic capacitors, and the surface-mount electrolytic capacitors from the early 90s are past their expected lifetime. In addition, despite the power supply being made by Sony, the capacitors in it are also known to leak (though I can't help think "cost tweaking" by Apple led Sony to use lower grade capacitors).
Last time we looked at the IIsi that would chime and then death chime, I found two broken traces and ran some bodge wires... only to have more data bit errors, not fewer. IIsigh. Before I start major drastic chip replacements on a now fragile PCB, let's take one last look at what Diagnostic Mode is telling us. Because I might have made a mistake running those bodge wires.
And if we get the IIsigh booting, we will finally full-send that promised 25MHz upgrade attempt.
Will Diagnostic Mode lead us to the error? Will the chat come in clutch (of course)? Will we see why the IIsi was so crummy after installing the 50MHz oscillator? You'll have to watch to find out!
*
Table of Contents
0:00:00 Pre-Roll
0:02:39 Greetings and Announcements
0:11:15 Wheel of Regrets™ (Who comes up with these titles anyway?)
0:11:38 Wheel of Regrets™: Western Digital WD1003V-SR1 Winchester (MFM) Disk Controller
0:16:25 Picking Up Where We Stopped Last Time with IIsi Number 4
0:45:36 Bodge Wires, Two Little Bodge Wires, Two Blue Bodge Wires, Where Are You [Going]?
0:48:27 Troubleshooting a Ko-Fi Notification Issue
0:52:09 I Finally Inspect the Board with a Multimeter
0:59:30 Oops, My Bad... IIsigh
1:03:00 Removing the Bodge Wires and Retesting
1:07:00 Troubleshooting a Discord Issue (by ending the task)
1:09:00 Continued Retesting and Chatting About Streaming
1:17:06 Talking About the Work Bench
1:29:10 Double-Checking Traces and Correcting the Bodge
1:38:37 Smoke Testing ("We've Got Progress Here Folks")
1:47:15 Five Little Megabytes of RAM, Ah, Ah, Ah! (Thunderclap)
1:52:28 BlueSCSIs Don't Work on the IIsi Unless You Got Power
1:58:00 Snooper 2.0 for a Few Cycles More...
2:11:44 Speedometer Baseline Benchmark
2:20:00 Baseline Benchmark Re-Do (without OBS Overlays)
2:29:30 Removing the Serial Cable and Replacing the System Bus Oscillator
2:48:10 Post Upgrade Speedometer Benchmark
2:57:00 Closing Thoughts
3:08:05 Outro
*
Ways to Support the Channel:
☕️ Tips or Support via Ko-fi: ko-fi.com/jdmcs
🈷️ Support me on Patreon: patreon.com/jdmcs
📦 Amazon Wishlist: jdmcs.net/wishlist
... or simply do the YouTube things: Like/Dislike, Comment, Subscribe, Enable Notifications, and participate in the Chat. These things help the channel, too!
**
Read Computerized Start™, my Official Blog: jdmcs.net/myblog
Follow me on Instagram: jdmcs.net/myinstagram
Follow me on Twitter: jdmcs.net/mytwitter
![Apple ][ Plus Clone Tantalum Troubles: Finding the Short on the 12V Rail (Computerized Start™ Live)](https://i.ytimg.com/vi/y_2k2MA5XMY/mqdefault.jpg "Apple ][ Plus Clone Tantalum Troubles: Finding the Short on the 12V Rail (Computerized Start™ Live)
Ive launched a merch shop: https://shop.jdmcs.com - use code JUSTINTIME for 5% off all Computerized Start™ merchandise through at least May 31th!
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I bought an Apple IIe Clone Motherboard on eBay (the place where I buy the things I later regret™) knowing full well it was an Apple ][ Plus clone motherboard and missing some chips. Yes, COMPUTER was jealous at first, but then COMPUTER realized I needed practice on a similar motherboard before I continue removing sockets, so were good...
Whats not good is this clone motherboard: there is a short on the 12V rail. But after removing all the chips that are on the 12V rail, the short was still present. Then I noticed it: a previous owner replaced ceramic capacitors with tantalum capacitors.
There are no polarity markings for these capacitors, so I suspect the board was designed for ceramic capacitors (like the Apple ][ Plus), and its likely one or more of these capacitors are installed backwards. Hopefully removing all the tantalum capacitors will remove the short, then Ill replace them with ceramic capacitors.
Will I find the short? Will the ceramic capacitors I bought make the board look original? Will I get to powering this motherboard up? Youll have to watch to find out!
*
Ways to Support the Channel:
☕️ Tips or Support via Ko-fi: https://ko-fi.com/jdmcs
🈷️ Support me on Patreon: https://www.patreon.com/jdmcs
📦 Amazon Wishlist: https://jdmcs.net/wishlist
... or simply do the YouTube things: Like/Dislike, Comment, Subscribe, Enable Notifications, and participate in the Chat. These things help the channel, too!
**
Read Computerized Start™, my Official Blog: https://jdmcs.net/myblog
Follow me on Instagram: https://jdmcs.net/myinstagram
Follow me on Twitter: https://jdmcs.net/mytwitter")
