Mac IIfx wont turn on (Replaced the batteries)

[Johnnya101]

Yes, its now the opposite of my older thread. Ive picked up a IIfx that wont turn on! I switched PSUs with my other good one, nothing. Replaced batteries. Nothing. 

At. All.

Im going to get both fully recapped. This ones board is perfect, like my other one... Only thing I can think of is the cap by the switch.

Any ideas?

 

[Johnnya101]

Progress!!

Tested with a keyboard to turn it on.

Instead of the startup "dyeewwwwwwww" it does

"Dye-" and shuts off...

...? Caps? It is somewhere on the logic board for sure. Could bad ram or something cause this?

 

[Johnnya101]

Well then... Opened it up again and one of the caps by the batteries slid to the right... The thing rotted through its pads. Gonna guess thats the issue?

Luckily it was only its pads and not everywhere.

 

[Themk]

well that's unfortunate. Are you sure the pad is a goner?

 

[Unknown_K]

You can desolder the pad form the capacitors leg and crazy glue it down on the board, let the glue dry, then solder bridge it to the trace (scrape a little of the board coating off with a exacto knife) or use a jumper wire to a test point. You would need to clean up the cap goo off first.

Just because the capacitors look ok from the top doesn't mean they have no leaked and made a mess underneath destroying solder pads or traces below.

 

[Johnnya101]

Yeah the pads totally gone. Sent unknown a photo. We will find out if it destroyed traces, however since I got it to sort of bong Id say its fine.

 

[Johnnya101]

Heres a photo! Im hoping all that brown is still just goo.

Sorry for the streaks everywhere, I attempted to clean up with a Q Tip, the board is gonna get a nice bath

 

[Unknown_K]

Progress!!

Tested with a keyboard to turn it on.

Instead of the startup "dyeewwwwwwww" it does

"Dye-" and shuts off...

...? Caps? It is somewhere on the logic board for sure. Could bad ram or something cause this?

I reproduced this when I recapped my machine that would not start up (one leg of a capacitor wasn't on good). Replacing those 2 caps also fixed the shutdown issue.

 

[Johnnya101]

Just an update a couple years later. Finally got it recapped. The user who did so found out there were a couple of rotted traces by those caps and had to run some patches.

Got it back together... And... It booted! Then gave death chimes a minute after. Bank A, which is 16mb, allows the II to boot, but if I add in bank B, 64mb, it gives death chimes during the memory test. Hopefully it just wasn't seated right because 64mb is hard to find.

This will sit for another few months until I can get to it. Both floppy drives have broken eject gears and the hard drive died. But at least it works now!

 

[IIfx]

FYI the IIfx has redundant set of pads for all capacitors in the system, the blank pads to the right would work. Apple made logic boards for the IIfx with both SMD electrolytic and Tantalum caps, depending on supply chain factors. My IIfx is about 80% Tantalum, with the last 20% being electrolytic. Even the large axial caps have pads underneath for a SMD cap!

 

[Johnnya101]

Both sets were rotted.

 

[IIfx]

Both sets were rotted.

Ah that's a shame, the photo makes it look like the 2nd set is salvageable. Missed the part about rotted traces.

This reminds me to recap my spare IIfx logic board. I did the main logic board already, that was a breeze compared to other Macs I have done.

 

[Johnnya101]

No idea how bad it was, all my recapper said was that both sets were rotted. The leaking was super super bad. Luckily it was just those two caps. The goo was so bad it of course ste through the traces and pads, but the cap was loose and rolling around!