Found a vintage Mac Plus, but it's got a "Sad Mac" and a weird wiring job inside. Any ideas?

[Huxley]

As I shared a couple days ago in the Conquests thread, I was lucky enough to find a Macintosh Plus with keyboard and mouse for $15. The seller did inform me that it beeps on power-up, but he never saw anything onscreen.

I've just gotten it home and tried it out. I find that it does indeed beep when I hit the power switch, and I do get an image on the display (though the image flickers like mad if the Mac or the table is moved / bumped / jostled at all), but unfortunately it's only showing me a Sad Mac with an error code "0102D1." Even more weirdly, on the underside of the motherboard is what looks to be a "DIY" patch-cable, linking one IC to another. Here's an album with some pics, including the patch-job I found. I'd really appreciate any tips or suggestions - I'd love to get this machine back to life!

Update: I carefully reseated both ROM chips and cleaned / reseated the RAM but it hasn't made any difference - the machine still Sad Macs upon boot  

 

[Huxley]

Made a quick video of the two issues I'm seeing - I hope this helps clarify what's going on!

 

[mattsoft]

I had a similar problem on a Plus and it was a cold solder joint on the analog board where the power molex connects. I simply reflowed the solder on the analog board for the molex connector and all was good. YMMV.

 

[unity]

And dont forget to reflow the solder on the mobo connector too.

 

[dochilli]

The error code 01 means that there is a problem with reading the ROM. The 02D1 is meaningless.

Perhaps you can change the ROM. As far as I know you can burn a new with 27C512 Eproms.

https://www.nightfallcrew.com/25/04/2014/macintosh-plus-sad-face-repair/

 

[Huxley]

Quick update: a lovely / kind person on Reddit has burned some fresh ROM chips for me, and even threw in a MacOS 6.0.x boot disk for me to use during testing, and they even refused any payment for all of this. The package should arrive sometime in the next couple days - if the Mac boots nicely with the new ROM's, I'll definitely move on to troubleshooting the analog board.

As someone with super basic / rudimentary soldering skills (and no fancy tools beyond a $15 Amazon soldering kit), are there any specific tips / tricks / tutorials you guys would recommend? I'm starting to look around on YouTube for tips (there are a lot!) and feeling a little overwhelmed...

 

[dcr]

As someone with super basic / rudimentary soldering skills (and no fancy tools beyond a $15 Amazon soldering kit), are there any specific tips / tricks / tutorials you guys would recommend? I'm starting to look around on YouTube for tips (there are a lot!) and feeling a little overwhelmed...

There was a useful video on YouTube someone posted last year I think that was basically an introduction to soldering that had a lot of good information in it.  I don't remember the thread, but hopefully someone will remember the thread or video and post a link.

The other thing I would recommend is to buy some inexpensive electronics kits.  I've gotten ones from AdaFruit, but SparkFun and many others have them.  That gives you good practice without risking screwing up a Mac, and you can instantly see results.  It can help build skill and confidence.

Does your soldering kit include a solder sucker?  If not, get one.  I don't know how I got along without one.