Macintosh Portable M5120 - Where to Bodge?

[thisisben]

After recapping my Portable it would no longer boot, no screen, no sound, nothing. After testing my way through the schematics, all caps that I've replaced test fine except for one.

From what I can tell, the positive side of C24 is no longer connected to anything, so I need to get that fixed up before testing again.

Looking at the schematics, C24 is connected through the Reset switch (S3), on it's way to the Power Manager (PMGR) chip.



Is it reasonable to bodge from the positive pad of C24 to the correct pin on S3? S3 to PMGR traces out fine, so I'm assuming getting the electrons from this C24+ to the reset switch would be a reasonable fix. Is that true?

Something like:

 

[oldpcguy]

That seems reasonable to me. Is there a via or something on the bottom of the board which you could attach to?

 

[thisisben]

There appears to be a very small via on the trace leading from the positive pad right next to the hybrid board, but that (I think) will be too difficult to patch into that unfortunately.

 

[oldpcguy]

Can (or do you want to) determine where the break is? If it's close to the capacitor pad perhaps you could scrape away some of the solder mask and bridge it. Then use some fingernail polish to cover the bridge. Otherwise the way you intend to bodge seems fine, if not ideal, to me.

 

[thisisben]

Poking around some more, I think I may have found the break so I'll attempt a more reasonable fix.

For testing last night, I wired a temporary bodge from C24+ around to the S3 switch leg and ... nothing. I was able to hear some hissing from the speaker, and when pressing a key on the keyboard to turn the Portable on, crackling from the speaker was all I got.

Interestingly, I wired the portable directly into my bench supply as described in https://68kmla.org/bb/index.php?threads/mac-portable-hybrid-combine-forces.40175/post-437684, and it worked! I haven't tried booting from disk/Floppy EMU but the machine started and appeared to be stable for an extended period of time and multiple reboots.

I guess that confirms the unfortunate reality that the hybrid on this machine is dying / already bad. I'll try to reflow the hybrid, but not holding out much hope for success with that.

 

[3lectr1cPPC]

If you can’t get the original hybrid to work, replacements are available here: https://androda.work/product/macintosh-portable-hybrid-module-recreation/

 

[thisisben]

Oh, that's awesome. I had seen chatter here around reproducing the Hybrid, but didn't know any were actually made. I ordered one, so we'll see what happens when I get this hybrid swapped out

 

[3lectr1cPPC]

Hope it goes well for you, and may your portable live another day!

 

[thisisben]

The Androda replacement hybrid worked great, and the portable is back up and running! Thanks again for the help.