Nama
Veteran Member
Hi everyone,
I'm a little reluctant to post this as I've had some rude private emails from a particular S-100 user when I posted a question on one of the S-100 forums...but anyway, here goes nothing...hopefully someone here has some experience fixing these and can point me in the right direction.
I am presently trying to fix a SOL-20.
I have removed all the extra cards and am now just trying to get the base unit booting. It boots up to garbage if switch 1-1 is in the on position. If it is in the off position I am getting a screen full of repeating square characters followed by '9' characters. Reading the SOL-20 build manual I have found a section talking about the video RAM, reading this I can assumed that this pattern actually indicates that the machine is at least accessing the video RAM and the video RAM seems to be working fine.
I then removed the onboard 8k of user RAM and have one by one replaced the video RAM with it. Occasionally the screen pattern would change in certain areas which tells me that the specific chip I just transposed is probably bad. Ultimately I found 3 bad RAM chips this way. I have just ordered some new RAM from ebay and it should be here in a week. Bad RAM is certainly one reason the machine is not booting.
Now with all the user RAM removed and switch 1-1 still in the off position I was now expecting to see either a blank screen, or a screen full of singular characters...something consistent at least. What I did get was a screen with lines of nothing and other lines of grey box characters, nothing too remarkable here, however there are also a few seemingly random characters on the screen. I say seemingly because there position actually does not change on subsequent restarts. The only thing that does seem to change is the character that is in the top left corner where I believe the cursor should appear. It's always in the same position, only the character changes. The other random characters, 'w's and '(' are always the same and in the same position. Take a look here:
http://web.me.com/lord_philip/other_computers/SOL-20.html
Anyway, I'm hoping the new RAM fixes things, but I have my doubts. If not then next I'll try to read the SOLOS ROM and see if it's still healthy.
Cheers
Nama
I'm a little reluctant to post this as I've had some rude private emails from a particular S-100 user when I posted a question on one of the S-100 forums...but anyway, here goes nothing...hopefully someone here has some experience fixing these and can point me in the right direction.
I am presently trying to fix a SOL-20.
I have removed all the extra cards and am now just trying to get the base unit booting. It boots up to garbage if switch 1-1 is in the on position. If it is in the off position I am getting a screen full of repeating square characters followed by '9' characters. Reading the SOL-20 build manual I have found a section talking about the video RAM, reading this I can assumed that this pattern actually indicates that the machine is at least accessing the video RAM and the video RAM seems to be working fine.
I then removed the onboard 8k of user RAM and have one by one replaced the video RAM with it. Occasionally the screen pattern would change in certain areas which tells me that the specific chip I just transposed is probably bad. Ultimately I found 3 bad RAM chips this way. I have just ordered some new RAM from ebay and it should be here in a week. Bad RAM is certainly one reason the machine is not booting.
Now with all the user RAM removed and switch 1-1 still in the off position I was now expecting to see either a blank screen, or a screen full of singular characters...something consistent at least. What I did get was a screen with lines of nothing and other lines of grey box characters, nothing too remarkable here, however there are also a few seemingly random characters on the screen. I say seemingly because there position actually does not change on subsequent restarts. The only thing that does seem to change is the character that is in the top left corner where I believe the cursor should appear. It's always in the same position, only the character changes. The other random characters, 'w's and '(' are always the same and in the same position. Take a look here:
http://web.me.com/lord_philip/other_computers/SOL-20.html
Anyway, I'm hoping the new RAM fixes things, but I have my doubts. If not then next I'll try to read the SOLOS ROM and see if it's still healthy.
Cheers
Nama
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