[Coco] Coco3 appears to be dead: green screen with no text.

[Frank Swygert]

I agree with Bob! I recall some of the CoCo3s had a problem with light 
corrosion on the contacts of the GIME as well. I'd pull the GIME then 
clean the contacts in the socket and on the chip with alcohol. A Q-tip 
works well. Then pull and re-seat all the memory chips. If you still 
have a green screen after that I'm afraid the 6809 is blown. That's a 
relatively common occurrence on all CoCos.

Cartridges in/out with the power on will eventually blow a 6809, since 
all the lines are out there on the port and the power line is right next 
to a data line. If you look at a late cartridge you'll note one land on 
the edge connector is a bit shorter than the others. That's the power 
line. It was shortened to reduce blown 6809s -- the power line doesn't 
contact a data line as easily if the cartridge is slightly crooked when 
going in/out. Early cartridges have all lands the same length.

Download my book from the website -- it has a trouble-shooting/repair 
section that outlines most difficulties.

-- 
Frank Swygert
Publisher, "American Motors Cars" 
Magazine (AMC)
For all AMC enthusiasts
http://farna.home.att.net/AMC.html
(free download available!)