I just fired up my Apple I replica a day ago (after checking my soldering work, which looked good.) Everything worked fine, but after a little while, the display system started bugging out -- e.g., when i used LIST in BASIC, the output would be formatted strangely and lots of characters would be dropped -- this behavior continued upon more LISTS, with different (random) char drops. This problem happens outside BASIC -- any writing out to display is goofed up like this.
Here's the weird part -- when I power down and leave the Apple I alone for awhile, it works fine! Then, after a little while, the strange bugginess creeps in again. It's less bad if I wait 10 sec between commands ... quite a strange problem.
It's as if the chars are not getting loaded right into the video-out char buffer...the text being sent in to the machine is getting saved right; the displaying is just screwed up.
Anyhow, I'm a bit of a newbie in digital logic, so I have no clear ideas of what could be wrong -- maybe a crystal is damaged? If you have any diagnoses, do you know how I could fix this?
I don't think I gave any particular bad bumps to the PCB or made any cold solder joints (btw, how can you determine if a joint is cold? Can it be done visually -- that is, do they look "dirty?" I don't think I have any, but I'm not sure, if they are not obvious upon visual inspection.)
thanks so much from a novice,