Switching Apple III mainboard from 12v to 5v

4 posts / 0 new
Last post
Verault's picture
Offline
Last seen: 23 hours 28 min ago
Joined: Dec 21 2017 - 14:19
Posts: 363
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.

Offline
Last seen: 6 months 4 weeks 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.
Verault's picture
Offline
Last seen: 23 hours 28 min ago
Joined: Dec 21 2017 - 14:19
Posts: 363
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.

Offline
Last seen: 5 hours 19 min ago
Joined: Jul 31 2014 - 17:48
Posts: 78
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

Log in or register to post comments