Dead Sega SC3000H

[Mike van Bokhoven]

  Hi everyone,

I've been working on a Sega SC3000H:
http://www.old-computers.com/museum/computer.asp?c=206

It seems to have the common problems that afflict these. Firstly, the 
7805 regulator was dead. I pulled it and gave the machine 5V from an 
external supply, and it ran fine - apart from what looked like a 
horrible RAM fault. I can see it's trying to do something sensible, but 
the display is corrupt. So, I tried the next test for obvious RAM 
failure - are any of the RAM ICs getting unusually hot? Seven were 
barely warm, but one is almost too hot to touch.

Now, this is annoying because I don't want to spend a great deal of cash 
on this machine, but I'd really like to get it going. I have two questions:
- Am I jumping to conclusions re the faulty RAM? The ICs aren't 
socketed, can anyone suggest any worthwhile tests?
- Does anyone know of somewhere I can get a MCM4517 P15 or equivalent, 
nice and cheap? One problem - I'm in New Zealand.

I'm a software guy really, but I do enjoy getting stuck into the 
hardware from time to time!

Mike