[Coco] Hello, newbie with new toy

[Frank Swygert]

I agree it's probably a bad CPU as that's the most common problem, but could be a bad ROM... though not very likely. I've run across one or two boards that had something bad that just couldn't be fixed, but that's rare. Those probably had 3-4 bad caps or resistors that just couldn't be tracked down without more hours than they were worth at the time. 

You may already know this, but....It's not hard to remove the CPU. Clip the legs off and leave them on the board, then heat and remove the legs one at a time. Some solder wick or a "solder sucker" removal tool works. The board is a pretty robust double sided design, not a multi layer like a typical PC. Use a pair of small needle nose pliers to grip the leg then heat and pull out, remove solder from hole after. Put a socket in, don't solder another CPU in there! Just don't pull too hard on the leg when heating it. It should come out easy, don't get impatient and force it. It's a relatively easy board to learn soldering on, not that the skill will help much on anything newer! All the new stuff is surface mount and really tiny traces and solder pads. But you can occasionally make a good wire splice and solder it! 

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Date: Mon, 29 Mar 2010 09:47:18 -0700 (PDT)
From: Jerry Morelli <jamorelli at att.net>

Thanks for the tip Frank.? I actually already downloaded "Tandy's Little Wonder" a couple weeks ago (what a great reference!? good job!) as one of the first things to get me back on the path to CoCo-land.? That's where I read about the GIME chip maybe being the culprit.? My next order of business was going to be to reseat the RAM chips just for the heck of it, but there are capacitors (I think) by the end of each one that seem like they'll make it hard to pry the chips up properly.? I started on one by prying the opposite end but got nervous and stopped.

Your suspicion, and mine, is that the 6809 itself might be bad.? That's what I'm afraid of.? I'm already dealing with some other problems with my main PC and I just don't have a lot of time to mess with the CoCo.? I got it because "it's simple"? ;-).? Oh, you are right that the only socketed chips are the GIME and the RAM, at least in my case.

I also don't think I can get the "3 musketeers" screen when resetting.? Is that a CTRL-ALT-Reset that does that?? So my suspicion is a bad CPU, which is just my luck.

-- 
Frank Swygert
Publisher, "American Motors Cars" 
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