[Coco] Back to the COCO

[Francis Swygert]

Date: Tue, 3 Jan 2017 14:33:11 -0500
From: Bill Gunshannon <bill.gunshannon at hotmail.com>
To: coco at maltedmedia.com

>> Well, good news and bad.
>> The bad, looks like the COCO3 is definitely dead. Power supply
>> tests fine so IO have to assume some chip has gone bad and I
>> doubt I have the ability to fix it.  One more for the pile of
>> dead 3's.  :-(
>

I'm just outside Scranton, PA.  Basically, the middle of nowhere.
I doubt anyone is near here.  I would love to have someone fix them
but I seriously doubt they are worth what it would cost. 2 hours
of bench-time exceeds their value by quite a bit.  And that's not
even considering parts if they are even available.

========================================
Bill, download a copy of "Tandy's Little Wonder" (http://www.colorcomputerarchive.com/coco/Documents/Books/   scroll down to T's and get the second edition). There are troubleshooting tips in there, you only need a VOM to do a lot of checking. The predominant problem with a dead or garbbled screen CoCo (any model) is a blown CPU. There are lines from the CPU that go directly to the cartridge port. One of those lines is right beside the power line. It's easy for a cartridge to be put in at enough of an angle to cross those lines, that's why the power line on all but the oldest cartridges is shorter than the other edge lands. Bumping an MPI with power on can do it. 6809E and 6309E CPUs are interchangeable. It's not that hard to clip the legs on the soldered in CPU and solder in a socket. You only have a few minutes of your time to lose, the CoCo is dead already...
 Frank Swygert
 Fix-It-Frank Handyman Service
 803-604-6548