[Coco] 2 MB upgrade in PAL coco3

[Mark Marlette]

Bob,

Anything is worth a try but I take the approach, since I have a lot 
of test equipment available to me. Once I know what the problem is 
then providing the proper solution....Engineer it. :)

Sorry that is just me. There is more than one way to fix a problem. 
You get it going, that is what you want. I get stuck in the design 
engineer rinse cycle. Always going bigger, better and then faster. :)

Good luck.

Mark


At 1/20/2008 06:47 PM, you wrote:

>Hi Mark,
>
>My first thought would be to insert a 74F04 in the clock line from 
>the crystal oven, to ensure that there is sufficient signal for the 
>upgrade. Sadly, I don't have an oscilloscope which will read this signal :(
>
>--
>Regards, Bob Devries, Dalby, Queensland, Australia
>
>Isaiah 50:4 The sovereign Lord has given me
>the capacity to be his spokesman,
>so that I know how to help the weary.
>
>website: http://www.home.gil.com.au/~bdevasl
>my blog: http://bdevries.invigorated.org/
>
>----- Original Message ----- From: "Mark Marlette" <mark at cloud9tech.com>
>To: "CoCoList for Color Computer Enthusiasts" <coco at maltedmedia.com>
>Sent: Monday, January 21, 2008 10:42 AM
>Subject: Re: [Coco] 2 MB upgrade in PAL coco3
>
>
>>Bob,
>>
>>Doesn't surprise me. Tony used an analog timing circuit with
>>components that we +/- 20%.
>>
>>I have one that I have never been able to get to work either. Mostly
>>because I look at the design and it is a waste of my time to tweak
>>the circuit. I would rather redesign and make the circuit digitally
>>timed and solid. Tweaking will always lead to tweaking. Worked for
>>Tony in the day when he supported it. Today there are MUCH better
>>ways to implement the timing required to put larger DRAMs in the CoCo.
>>
>>Grab a scope and chase those trons.....Tweak away......When you are
>>done you will be an expert in the CoCo's refresh. :)
>>
>>Regards,
>>
>>Mark
>>
>>
>>
>>
>>
>>At 1/20/2008 06:29 PM, you wrote:
>>
>>>Hello, fellow coconuts.
>>>
>>>I brought this topic up some time ago, with no resolution, so I'll
>>>present it again.
>>>
>>>I have a Disto 2MB upgrade board here that I have tried to install
>>>into my Australian PAL coco3. Physical installation was fine, but...
>>>it just doesn't work.
>>>
>>>I believe there was at one time a discussion regarding this problem
>>>on either Delphi or Compuserve. If anyone has the complete
>>>transcript of this, or has knowledge of the problem, I'd appreciate
>>>getting the information.
>>>
>>>My guess is that it is a timing problem, or the clock signal used
>>>isn't correct somehow. The only change from the installation
>>>instructions is the connection of the clock signal. On the
>>>Australian Coco3, the master clock is supplied by a crystal oven;
>>>one of those small rectangular metal minidip devices with 4 pins.
>>>This signal connects to pins 2 (signal) and 3 (ground) of the GIME.
>>>I connected the upgrade clock signal to pin 2 of the GIME. The
>>>crystal oven's frequency is 28.475 MHz.
>>>
>>>Can anyone help with this?
>>>
>>>--
>>>Regards, Bob Devries, Dalby, Queensland, Australia
>>>
>>>Isaiah 50:4 The sovereign Lord has given me
>>>the capacity to be his spokesman,
>>>so that I know how to help the weary.
>>>
>>>website: http://www.home.gil.com.au/~bdevasl
>>>my blog: http://bdevries.invigorated.org/
>>>
>>>
>>>--
>>>Coco mailing list
>>>Coco at maltedmedia.com
>>>http://five.pairlist.net/mailman/listinfo/coco
>>>
>>>
>>>
>>>
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>
>
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>>
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>
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