[Coco] CoCo 2 problem

[Chad H]

Good point, and I will most likely do that as well since I believe I already
have a spare socket for that and a sleeve of spare Hitachi HD68B09EP's  (no
not the 6309's, apparently Hitachi's own 6809 chips)

-----Original Message-----
From: coco-bounces at maltedmedia.com [mailto:coco-bounces at maltedmedia.com] On
Behalf Of Arthur Flexser
Sent: Saturday, August 06, 2011 10:59 PM
To: CoCoList for Color Computer Enthusiasts
Subject: Re: [Coco] CoCo 2 problem

You might want to also (first?) try socketing and replacing the 6809.
Seems like every time I had a hardware problem, the culprit turned out
to be the CPU.

Art

On Sat, Aug 6, 2011 at 11:28 PM, Chad H <chadbh74 at hotmail.com> wrote:

> Ok it seems it would be too costly to have someone else repair the board

so

> I'm going to take my time and take a crack at replacing the RAM chips

myself

> to start with..unsoldering the existing ones and installing socketed RAM.

 I

> purchased a "CoCo 64K upgrade kit" off ebay that consists of the 8 x 4164

> chips I've heard about.  I'm "assuming" that these will work in place of

the

> 8 identical RAM chips already soldered in.  However, I cannot find any

> information on the factory installed chips anywhere.  They are 8 x 16-pin

> DIP, labeled "8042665 / FQD8433" with "TC" and Motorola Logos.  Anyone?

>

> -----Original Message-----

> From: coco-bounces at maltedmedia.com [mailto:coco-bounces at maltedmedia.com]

On

> Behalf Of Chad H

> Sent: Thursday, August 04, 2011 10:58 PM

> To: 'CoCoList for Color Computer Enthusiasts'

> Subject: Re: [Coco] CoCo 2 problem

>

> I was kinda leaning towards "failed ram" as the most likely culprit.

> Unfortunatley, with this particular board, almost all chips are soldered

in

> place.  While I can solder 'OK' sometimes, I wouldn't want to risk

damaging

> the board or making a mess by taking a crack at it myself.  I'm wondering

> how expensive it would be have someone replace the RAM chips with socks,

> maybe even the soldered 6809 as well.  Would like to get it back to full

> operation if is not overly expensive.

>

> A photo of the board is here... http://www.mediafire.com/?12hf7zus7ebl49x

>

> Would anyone be interested in such a soldering task?

>

> - Chad

>

> -----Original Message-----

> From: coco-bounces at maltedmedia.com [mailto:coco-bounces at maltedmedia.com]

On

> Behalf Of Michael Graham

> Sent: Thursday, August 04, 2011 7:38 PM

> To: CoCoList for Color Computer Enthusiasts

> Subject: Re: [Coco] CoCo 2 problem

>

> I had a similar problem with my CoCo 3 once, and re-seating the RAM

> chips fixed it.  I can't remember whether the RAM is socketed in any of

> the CoCo 2 models - If it is, try re-seating it, if it isn't, it could

> be one or more of your RAM chips has microfractures in it, which are

> causing the chip to fail as the casing expands from the heat produced by

> operation.

>

> Don't take me as an expert on this though, I'm only speaking from two

> experiences I've had with this kind of thing - Once with my CoCo 3, and

> once with my TI-99/4a (the latter actually had all of its RAM chips

> fail). The microfracture thing is a theory I read from someone else.

>

> On 8/4/2011 7:30 PM, Chad H wrote:

>> Ok, I just acquired a new CoCo 2 unit (26-3127B) of unknown condition.

> The

>> unit looks immaculate inside and out, I had good hopes.  It did operate

>> great for about 5 minutes then started acting funny with disk access.  I

>> turned off the computer and rebooted and would either get garbage

(columns

>> of funny text characters) or a good boot screen (Microware copyright

>> statement with "OK") but there is no flashing cursor.  Anyone ever see

> this

>> behavior before or know what it probably is?

>>

>>

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