[Coco] CoCo 1 64K upgrade failed :(.

[Gene Heskett]

On Friday 26 September 2008, Ryan Pritchard wrote:

>I got to thinking this afternoon that there should be nothing preventing me

>from taking 41256 chips and merely grounding out pin 1 (A8) to keep the

>signal LOW (or is it HIGH? I don't remember my electronics logic that well)


It won't matter.  I'd tie them low, because the 5 volt line is probably too 
high.


>to allow me to use the chips to provide access to the 64K using the A0

>through A7 lines with the state of A8 always locked.  A0 - A7 on the DRAM is

>MA0 - MA7 according to CoCo Technical Manual.

>

>I wonder if I have an old 8 chip 256K VGA video card kicking around.

>

>On Thu, Sep 25, 2008 at 9:08 PM, Ryan Pritchard <coconut at pritchard.ca>wrote:

>> Hi all,

>>

>> I followed the instructions for the 32K / 64K upgrade that I was provided.

>>  I compared all 3 to 4 versions including a 32K only one.  The nice part

>> was the 32K only upgrade was the same steps for the 64K upgrade sans some

>> extra jumper wires.

>>

>> I only got as far as having desoldered my 64K x 1 DRAM from my extra Apple

>> //e 80 Column Card, and following the steps up to the end of the 32K

>> upgrade instructions.

>>

>> The CoCo does not boot.  I have cut all eight of the correct capacitors

>> C31, C35, C45, C48, C61, C64, C67, C70, moved all the jumpers to the 32K

>> setting, and tried both the LOW and the HIGH back jumper positions.

>>

>> I think I may have burnt out the 64K x 1 DRAMs.  I don't know what else it

>> could be and since I removed all eight caps breaking a couple in the

>> process I can't return to the 16K system :(.

>>

>> I guess my options are find a good set of 64K x 1 DRAM, or cut my losses

>> and pick up a CoCo 3 from Cloud 9.

>>

>> Currently kinda frustrating because the Extended Color Basic ROM I got

>> confirmed the FDC works.

>>

>> Regards,

>>

>> Ryan Pritchard

>> Fun Extends All Basic Life Expectancies




-- 
Cheers, Gene
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
I don't think I'm gonna agree with that.  Way too much visual confusion...
             -- Larry Wall in <199709021627.JAA11966 at wall.org>