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Hello,

 

I have have a couple old school Macs that I tinker with from time to time.  My favorite is my LC520 that I bought new and later upgraded with a LC575 motherboard and a PPC upgrade card.  I break it out from time to time, but don't really have space in my office to keep it out permanently.  So I decided I'd pick up a LC475 that wouldn't take up quite as much space.  I found one that looked to be a bit of a bargain and was told it chimed at startup but couldn't be tested without an adapter for the video.  I decided to take a chance on it, but it turns out it does chime at boot but never displays any video.  Inspection of the logic board shows what appears to be a chip that cracked and burned .  I'm assuming this chip has something do to with the video output, but I haven't had any luck in my search for details or a replacement.  Does anyone have any knowledge about this chip and if it might be possible to find something to replace it with?

 

Thanks for any insight you might be able to provide.

 

LC475 Board.jpeg

LC475 Broken IC.jpeg

Edited by KCChris
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The cracked chip may not be helping, but equally might actually be fine.

 

First, assuming you haven't tried this already, try with a PRAM battery installed, I notice there isn't one in the photo. The 475 needs it to output video.

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Thanks @joshc for your response.  I can't believe my searching on this issue didn't uncover that the LC475 needs a PRAM battery.  I was so focused on how the damaged chip might impact the video that I missed the general PRAM warning.

 

The PRAM battery in this system was completely dead when I got it, reading zero volts on a voltmeter.  Owning a SE/30 with a rusted chassis and a scorched motherboard from a Maxell blowout has gotten me into the practice of just removing all my PRAM batteries.  In this case, that was causing the video issue because I cobbled together a makeshift PRAM solution using a LiFePO 4 battery I had laying around and the system booted right up with video.  I have some proper PRAM batteries on order now.  So thanks for taking the time to post a quite helpful response, even though I probably should have found this issue on my own through some better searching.

 

Now that I'm up and running, I was going to ask what issues I might be running into with this damaged chip, but thanks to @techknight 's details on serial ports I was able to hook up an old modem and confirm that the modem port is not active, though the printer port is.  I could probably live with this issue given that I have no intent to actually try dial-up on this system, however I picked it up to tinker with it so I may explore repairing it a bit.  The downside is that I have not been able to find an exact replacement of this chip.  I think it's a chip from Motorola.  Some of the different LC models I have seen have this 2630A chip (my LC520 for example) and others have one from a different supplier with part number AM26LS30JC (i.e my LC575.)  I've done searches for LC motherboards and I can find LC III's with both versions of the chip.  So what's the chance that I could remove this 2630A chip and replace it (and maybe the other one) with a AM26LS30JC and it will work? 

 

I attached a couple pictures.  The first is the AM26LS30JC chips on a LCIII motherboard.  The second is the AMD version I can find that doesn't have a ridiculous minimum quantity requirement.  Think it might work?

 

Thanks for the help.

Chris

LC3.jpg

s-l500.jpg

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