Hi All,
I have just started to repair a Europlus which has a strange issue. The machine will boot to the applesoft “Apple ][“ ] prompt, and will even allow a small basic program or a call -151 to run. After a small amount of time white block start to appear on the screen in the place of spaces or empty space.
If I just hold down the enter key the spaces will start to appear, becoming more frequent with each new line.
Eventually the machine will get in a state where any basic program in memory will become corrupted. If i reset the machine or quickly power off/on - the artifacts occur straight away.
If I physically remove the PSU connetor and leave the machine for 30 seconds it will boot as normal and the fault will reoccur as above.
I’m pretty sure this is a RAM related issue as I also have bitfixer-romulator which I can use to provide a RAM replacement with “write through” memory for the video, with this enabled the video still corrupts but my basic programs do not and the machine is stable but shows the video artifacts.
I originally swapped chips with another Europlus, so i’m reasonably confident that most chips are good and I have also checked out all the resistors on the board (in place) and checked the smalls caps for shorts (although only in place).
Visually the board looks ok but does have some marks on the top layer traces (the bottom layer is fine) - an end to end test of a few traces shows no issue though. The fact that the machine initially boots ok but then corrupts after a period of time makes me think it’s not the traces.
One other difference between the faulty board and my other europlus is the board version, with the faulty board having socketed 555’s and 2 x 8T28’s rather than an 8304.
Does anyone know if the 555 or 8T28’s could cause these issues as I dont have a replacement for them?
Any help appreciated.
Regards
R
I have just started to repair a Europlus which has a strange issue. The machine will boot to the applesoft “Apple ][“ ] prompt, and will even allow a small basic program or a call -151 to run. After a small amount of time white block start to appear on the screen in the place of spaces or empty space.
If I just hold down the enter key the spaces will start to appear, becoming more frequent with each new line.
Eventually the machine will get in a state where any basic program in memory will become corrupted. If i reset the machine or quickly power off/on - the artifacts occur straight away.
If I physically remove the PSU connetor and leave the machine for 30 seconds it will boot as normal and the fault will reoccur as above.
I’m pretty sure this is a RAM related issue as I also have bitfixer-romulator which I can use to provide a RAM replacement with “write through” memory for the video, with this enabled the video still corrupts but my basic programs do not and the machine is stable but shows the video artifacts.
I originally swapped chips with another Europlus, so i’m reasonably confident that most chips are good and I have also checked out all the resistors on the board (in place) and checked the smalls caps for shorts (although only in place).
Visually the board looks ok but does have some marks on the top layer traces (the bottom layer is fine) - an end to end test of a few traces shows no issue though. The fact that the machine initially boots ok but then corrupts after a period of time makes me think it’s not the traces.
One other difference between the faulty board and my other europlus is the board version, with the faulty board having socketed 555’s and 2 x 8T28’s rather than an 8304.
Does anyone know if the 555 or 8T28’s could cause these issues as I dont have a replacement for them?
Any help appreciated.
Regards
R