• Hello, Guest! Welcome back, and be sure to check out this post for more info about the recent service interruption and migration.

ALS 245 fell off IIsi, possible to fix?

pball52998

Well-known member
Hello!

First post here and growing retro Macintosh enthusiast.

I grabbed a IIsi from goodwill about 8 years ago for $5, took the battery out and never touched it again knowing I'd get to it eventually.

Unfortunately it seems that the top UE5 ALS245 just.. fell off due to corrosion from what would either be battery leakage / PSU leakage.

I've since taken off all the caps, cleaned the board through and through, the PSU, everything.

Unfortunately I can't find a schematic or a understanding of what the UE5 ALS245 chip or any of the ALS245 chips do.

What is the possibility of fixing? Worth fixing? Or any tricks I could do to actually ever see this thing working?

If not, I'll use it as a practice board for other projects, such as working to be better at re-cap/soldering/etc

Thanks for any input!
 

Attachments

  • PXL_20221108_133221054.MP.jpg
    PXL_20221108_133221054.MP.jpg
    4.7 MB · Views: 35

pball52998

Well-known member
I think this is a bus driver. You should easily find a replacement.
I still have the chip thankfully and can clean it. Would it be as simple as soldering it back on?

probably a 74LS245 (in SOP version) Octal Bus Transceiver
Could you expand a bit on this, just curious on it. Guessing like this? https://www.ti.com/lit/ds/symlink/74ac11245.pdf?ts=1667848250710&ref_url=https%3A%2F%2F

I had another fall off also.. Unfortunately I haven't been able to really find where this one even went.

Forgot about it until I went to look again. Any ideas on this guy? Labeled K1402A

Thanks again for the prompt help!
 

Attachments

  • PXL_20221108_135745541.MP.jpg
    PXL_20221108_135745541.MP.jpg
    4.5 MB · Views: 30

pfuentes69

Well-known member
I still have the chip thankfully and can clean it. Would it be as simple as soldering it back on?
It should be possible, unless the legs are too corroded. This is a low cost IC (74ALS245), so not a big deal if finally you have to replace it.

Not clear what could be other thing... power regulator?
 

pball52998

Well-known member
It should be possible, unless the legs are too corroded. This is a low cost IC (74ALS245), so not a big deal if finally you have to replace it.

Not clear what could be other thing... power regulator?
Yeah looks to be a power regulator.. just can't find to what. I picked it up without HDD/Floppy so I wonder if it was off of one of those and just cracked in half in the case.

Hope I can get this thing up and running in the next few months, pulled a floppy from my beige G3 that seems to be compatible and got all the things to recap.
 

robin-fo

Well-known member
Be aware that the ALS245 are being sold in two sizes which look very similar. You need the bigger ones. I ordered the smaller ones for my IIsi and they almost didn‘t fit
 

imactheknife

Well-known member
I might have an extra i can pop in letter mail from Ontario. Will check my stash. I had to replace that exact chip due to corroded feet on a iisi from those nearby 47uf caps
 

pball52998

Well-known member
I might have an extra i can pop in letter mail from Ontario. Will check my stash. I had to replace that exact chip due to corroded feet on a iisi from those nearby 47uf caps
That would be great! Would love to get it up and running.

Let me know if you have an extra
Thanks!
 
Top