ZX80 troubleshooting with oscilloscope.
Posted: Sat Dec 28, 2019 4:01 pm
Hello.
I got an oscilloscope for Christmas! I won't pretend I know how to use it.
I thought I could use it to find out why my ZX80 Russian clone isn't behaving properly. Problem: there is no K cursor. When I power it on it flickers with a brief black horizontal line (which appears normal), goes completely white and that's it. It has a ZX8-CCB attached, as you can see (and I've played with the trimmers to get a stable pic):
All of the chips appear to be correct and round the right way. The Eprom is a 2732 and the board has little solder jumpers on the back to enable use of a 2732.
On the video out I get this signal (ignore the missing red line sections, that's down to crappy screenshots):
Which I think is normal.
Pin 6 (clock) on the Z80 looks like this:
Which again, I believe is as it should be.
Pin 19 on the Z80 (MREQ) looks like this (but does seem a bit flickery when it's not a still like that):
Is there an idiots guide to what I should check?
I got an oscilloscope for Christmas! I won't pretend I know how to use it.
I thought I could use it to find out why my ZX80 Russian clone isn't behaving properly. Problem: there is no K cursor. When I power it on it flickers with a brief black horizontal line (which appears normal), goes completely white and that's it. It has a ZX8-CCB attached, as you can see (and I've played with the trimmers to get a stable pic):
All of the chips appear to be correct and round the right way. The Eprom is a 2732 and the board has little solder jumpers on the back to enable use of a 2732.
On the video out I get this signal (ignore the missing red line sections, that's down to crappy screenshots):
Which I think is normal.
Pin 6 (clock) on the Z80 looks like this:
Which again, I believe is as it should be.
Pin 19 on the Z80 (MREQ) looks like this (but does seem a bit flickery when it's not a still like that):
Is there an idiots guide to what I should check?