Re: A2 Rev 0 Recreation Update #2

["Michael J. Mahon" <mjmahon@aol.com>]

Mike Willegal wrote:
> Hi Folks,
>
>   After taking my time soldering on the components, I powered on 
> yesterday with 16k of memory installed.  Initially I got no video. 
> Probing found no clocks at all.  Traced it down to wrong transistors in 
> clock circuit.  After taking the right ones from an old rev4 board, it 
> came to life, but no text - video mode only.  I found a bad IC.  The 
> 74166 at location A3 had a bad output.  I did another swap from the rev 
> 4 board and now I had a text prompt, but no color.  Swapped the crystal 
> from the rev4 and color appears. 

There are two types of crystals:  series resonant and parallel
resonant.  Sounds like you need the "other" type (and I don't
recall which it is ;-).

> Tried booting DOS and it dropped to 
> monitor instead.  After thinking about it a while, remembered that I 
> needed more than 16K ram to run DOS.

If you boot a DOS "master", 16KB is enough.  But a "slave" DOS will
require/use as much RAM as the machine it was INITed on (unless you
convert it to a master using MASTER CREATE on the DOS Master disk).

>  Filled up memory to 48k and now I 
> could boot DOS.  Booted from all the slots successfully.  Next I checked 
> out the pdl and switch inputs - all work fine.  I still have to check 
> out annunciator outputs, Slot 0 functionality, cassette I/O and a 4K 
> memory configuration.
>
>   The bottom line is that, except for some minor component issues, 
> things are looking real good.  It will take a few more days to check out 
> remaining functionality and probably several more weeks to sort out 
> remaining component issues and put together a rough guide to building 
> and bring up the board.

Sounds good!

>   I put some preliminary information on my site about availablity and 
> cost of kits.  Goto the apple II recreation page for more information.
>
> Regards,
> Mike Willegal
>
> www.willegal.net

-michael

NadaPong: Network game demo for Apple II computers!
Home page:  http://members.aol.com/MJMahon/

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