Mega 1 to 4 Mb (C103277 Rev2.2)
Posted: 15 Jun 2019 10:41
Inspired by Troeds and Franks post I thought I do a upgrade on a deeply yellowed Mega 1 I got for 20Euro on Ebay as a parts/non working machine. One of them only had a faulty PSU.
My Mega 1 has the RAM chips soldered as a dip package on the board. It's a C103277 Rev2.2.
So I bought the same SOJ to DIP adapters Troed bought. Also got a 72pin 8MB RAM stick with 60NS chip on it for 10Euro since I probably going to upgrade another Atari. So only need 8 of the chips on the board. Some pin header strips, kynar wire and a 33Ohm resistor is also needed as well.
Desoldered the RAM from the motherbord and from the 8MB Ram stick.
The pin headers can't be put in as normal so you have to push them in a bit and solder them flush with the adapter board otherwise the SOJ RAM chips will not fit. The plastic strips on the header can be moved by just pressing them against a hard surface with pliers. I also sanded the adapter boards to get them to fit snugly on the motherboard since I don't want them to be tilted.
Run a wire between all pin 5 (adress line A9) and pin 64 on the plcc MMU (MAD9) with a 33ohm resistor in between. It's pin 66 if you got a smd MMU.
My Mega 1 has the RAM chips soldered as a dip package on the board. It's a C103277 Rev2.2.
So I bought the same SOJ to DIP adapters Troed bought. Also got a 72pin 8MB RAM stick with 60NS chip on it for 10Euro since I probably going to upgrade another Atari. So only need 8 of the chips on the board. Some pin header strips, kynar wire and a 33Ohm resistor is also needed as well.
Desoldered the RAM from the motherbord and from the 8MB Ram stick.
The pin headers can't be put in as normal so you have to push them in a bit and solder them flush with the adapter board otherwise the SOJ RAM chips will not fit. The plastic strips on the header can be moved by just pressing them against a hard surface with pliers. I also sanded the adapter boards to get them to fit snugly on the motherboard since I don't want them to be tilted.
Run a wire between all pin 5 (adress line A9) and pin 64 on the plcc MMU (MAD9) with a 33ohm resistor in between. It's pin 66 if you got a smd MMU.