Switching Apple III mainboard from 12v to 5v

4 posts / 0 new
Log in or register to post comments
Last post
October 6, 2020 - 10:15pm
#1
Verault
Verault's picture
Offline
Last seen: 5 months 1 week ago
Joined: Dec 21 2017 - 14:19
Posts: 372
Switching Apple III mainboard from 12v to 5v

So i found this document that talks sbout the different IC's needed to convert a 12v apple III system bosrd to the 5v system :  https://www.apple3.org/Documents/Technotes/TA31049.html

 

I have an apple III system board i repaired by using a 12v memory board from another working system. I do have a spare working 256kb 5v ram board so i have to convert the system board over to use the 5v 256kb rsm. Where can i find these roms? Has anyone done this change before? Need info on this. Thanks guys.

Top
October 6, 2020 - 11:25pm
dc99
Offline
Last seen: 1 year 2 months ago
Joined: Jul 5 2016 - 19:01
Posts: 49
Those proms are available
Those proms are available online (http://www.bitsavers.org/pdf/apple/apple_III/firmware/A3PROMs.zip) however they are Bipolar PROMS so you will need an older programmer to burn new ones.
Top
October 7, 2020 - 8:32am
Verault
Verault's picture
Offline
Last seen: 5 months 1 week ago
Joined: Dec 21 2017 - 14:19
Posts: 372
Thanks DC99 I know a guy who

Thanks DC99 I know a guy who can still burn those old PROMS so ill get these files to him! Thats great.

Top
October 8, 2020 - 8:11am
rjustice
Offline
Last seen: 1 day 1 hour ago
Joined: Jul 31 2014 - 17:48
Posts: 85
Here is the 256k upgrade

Here is the 256k upgrade procedure. This will give you a bit more information needed for this.

https://www.dropbox.com/s/1xqtyf1jhfhs90m/Apple3%20256K%20RAM%20Upgrade%20Procedure.pdf?dl=0

Top
Log in or register to post comments