One tip - try moving the display gently back and forth in your 1400. I have one that's prone to some video issues, and it's always been as a result of the display cable getting crimped somehow. Moving the hinge always resolves it eventually.

I have seven 1400s, and have never had to extract the dead PRAMs to get startup to work ok. Occasionally I have to unplug the cable in my Pismos, but that battery is much easier to get to.

Hope you can resolve this...the 1400 is still a very nice little machine to write on.