• Please review our updated Terms and Rules here

Apple ][ plus 48k won't boot, please help me sort it.

R

ronpepin

New Member
Joined
Apr 28, 2021
Messages
3
I recently attended a VCFeast swap meet - it was fantastic being able to attend an in-person event! In any case, there I bought an apple ][ plus computer with no cards & 2 drives.

I ordered some parts, a keyboard encoder, a disk controller card, etc. I am so excited to get this running. I have a problem, however - the machine does not boot (yet)

could someone maybe get me going on the right track to solve this. Right now, I` get a screen full of characters in the following pattern:

??@@??@@??@@??@@??@@??@@
??@@??@@??@@??@@??@@??@@
etc

I have tried re-seating the ram chips in row D, and I have transposed the DIPs positioning.
I have reseated the ROMs
I moved a known working 6502 processor and switched out the proc on the board

none of these things have as of yet yielded any result.

I don't have an oscilloscope (yet) so I cannot really test the individual cpu lines.

Can someone please point me in the right direction?

When this computer was new, I was also new, and now we are both old. It's sort of one of those kind of situations (nostalgia). I never owned an Apple II, I was a c64 kid in the 80s and then Mac and Amiga in the 90s. I am quite excited to join the Apple II contingent, if possible.

Thanks,
Ron
 
Points more to ram or rom to me.

The Apple II will boot with only row C populated so have you tried removing all the ram and seeing if you can find a set that will enable it to boot in row C only ?

Cheers
Andy
ronpepin said:
I recently attended a VCFeast swap meet - it was fantastic being able to attend an in-person event! In any case, there I bought an apple ][ plus computer with no cards & 2 drives.

I ordered some parts, a keyboard encoder, a disk controller card, etc. I am so excited to get this running. I have a problem, however - the machine does not boot (yet)

could someone maybe get me going on the right track to solve this. Right now, I` get a screen full of characters in the following pattern:

??@@??@@??@@??@@??@@??@@
??@@??@@??@@??@@??@@??@@
etc

I have tried re-seating the ram chips in row D, and I have transposed the DIPs positioning.
I have reseated the ROMs
I moved a known working 6502 processor and switched out the proc on the board

none of these things have as of yet yielded any result.

I don't have an oscilloscope (yet) so I cannot really test the individual cpu lines.

Can someone please point me in the right direction?

When this computer was new, I was also new, and now we are both old. It's sort of one of those kind of situations (nostalgia). I never owned an Apple II, I was a c64 kid in the 80s and then Mac and Amiga in the 90s. I am quite excited to join the Apple II contingent, if possible.

Thanks,
Ron
Click to expand...
 
Last edited:
Thank you so much for your replies. So, I have tried removing all ram except row C, with the same result. I also tried moving out different sets of ram into that row and I basically got the same result. I am sure I have some bad ram, because there were some cases where I had different results, not the same ??@@??@@??@@ pattern, but something different, but generally I have not yet gotten anywhere.

Is there some source of these chips that I could just replace all 48k with new?

thanks,
Ron
 
The chips often lose contact with the sockets over time so the first thing I do with a II+ that's not working correctly is to reseat all the chips
 
RAM is not the only component that produces this pattern if it fails.
Does the computer beep at power up ?
 
This web page may give you an indication of which chips to look at next perhaps. There is likely to be a problem on the databus and/or address bus. Do you have a MiniPro programmer that can test IC’s (assuming the roms are good) ?

https://www.applefritter.com/appleii...esurection.htm
 
Last edited:
You must log in or register to reply here.
Back
Top