I think I know what’s wrong with this iie...

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I think I know what’s wrong with this iie...

While browsing on eBay looking at iie motherboards, I found this listing...

The seller says that when it's turned on, nothing comes on the screen.

Maybe it has something to do with the missing LS125 chip?

https://www.ebay.com/itm/195259271348

Oops!

Time for someone here to get a replacement iie board for cheap.

The seller is using the, "or best offer" option.

Oh! When a iie has no video, it's an expensive problem to fix! It's going to cost me $134,335,977 just to get that motherboard diagnosed properly! After that, the parts are so hard to find, I may never fix that thing!

I offer you $5.87. It's worth almost nothing.

You know, you're lucky you're getting an offer at all for that worthless iie!

CVT
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It would be wrong to assume

It would be wrong to assume that once you put back the missing LS125 you would have a working motherboard. The seller has probably tried that, considering he's got a vintage electronics store on eBay. If he has a spare power supply from another machine to try it, then he could have easily borrowed the LS125 and pop it in to see if he actaully has a working motherboard with one missing chip. 

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CVT wrote:It would be wrong
CVT wrote:

It would be wrong to assume that once you put back the missing LS125 you would have a working motherboard. The seller has probably tried that, considering he's got a vintage electronics store on eBay. If he has a spare power supply from another machine to try it, then he could have easily borrowed the LS125 and pop it in to see if he actaully has a working motherboard with one missing chip

 

 

This -- chances are it is one of the unobtanium chips (MMU or IOU) that are bad.  They probably stole the commonly availble 74LS125 to fix a broken floppy drive or something.

 

FWIW, I have two parts //e motherboards here that need MMU chips.  Someone needs to make a replacement for the MMU and IOU using GALs, CPLDs or FPGAs.  I think it might be possible with 2-3 ATF750C SIOC package chips mounted on a 40 pin DIP carrier.  I just don't know enough about programming .pld to do it.  The Jim Sather "Understanding the Apple //e" book has a block diagram and description of what the MMU (and also IOU) chip does.  Its just a little beyond me at this point.

 

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Maybe still wanna pick it up.

Maybe still wanna pick it up. Not likely both IOU and MMU are bad at the same time. And these parts are going to get harder to find. And any future replacement will likely be $50 or more anyways. So get while the gettings' good.

CVT
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I wouldn't pay more than $30

I wouldn't pay more than $30 for it though. An identical motherboard just sold for $60 on eBay, except that it was tested and working: click!

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