IIsi logic board questions (capacitors and J19)

[dv-]

IIsi has visibly swollen capacitors so I ordered some replacements. I got the little square tantalum ones because I read they don’t leak. I double checked the markings and supposedly they are 47uf 16v, which should match what’s on the board.

https://a.co/d/6pa0oPv

Installed the first one, powered it on, and it exploded. Wondering what I might have done wrong.

Also, I’m wondering what the J19 connector on the logic board (by the floppy drive) is for? Tech manual only says not to touch it.

 

[zigzagjoe]

IIsi has visibly swollen capacitors so I ordered some replacements. I got the little square tantalum ones because I read they don’t leak. I double checked the markings and supposedly they are 47uf 16v, which should match what’s on the board.

https://a.co/d/6pa0oPv

Installed the first one, powered it on, and it exploded. Wondering what I might have done wrong.

Also, I’m wondering what the J19 connector on the logic board (by the floppy drive) is for? Tech manual only says not to touch it.

You might have reversed the polarity. Tantulums mark positive, not negative.



If the polarity is correct, there's a possibly that it was overheated during the install process though that does take quite a bit to do. 10+ seconds of continuous soldering iron contact, I'd say.

 

[dv-]

You might have reversed the polarity. Tantulums mark positive, not negative.

View attachment 78977View attachment 78978

If the polarity is correct, there's a possibly that it was overheated during the install process though that does take quite a bit to do. 10+ seconds of continuous soldering iron contact, I'd say.

Crap that’s exactly what I did. *facepalm*

Thank you.

 

[zigzagjoe]

Crap that’s exactly what I did. *facepalm*

Thank you.

Happy to help. I think everybody blows up a tantulum the first time

 

[cheesestraws]

Yes, you are far from alone here. The decision to mark the other end on tantalums from electrolytics was ... not, perhaps, entirely sensible.

 

[dv-]

Finished with it this morning; the IIsi is now in fully working order!