Date   : Sat, 29 Jun 1996 13:11:55
From   : pnt103@...
Subject: More video problems

Steve (Loft) wrote:

> I thought I'd go round and reseat all the socketed chips again, in case I
> missed any last time.  Now, in any mode other than 7, I don't see the top
> half of the characters, I just get the bottom half repeated twice - with a
> similar effect for graphics.

> Any idea what I might have done?  I've had a good look at all the chips,
> and I can't see any bent pins, or any not in the socket.

My first thought is that one of the address lines from the video circuit to
the RAM is being ignored.  Either you've missed a bent pin, or you have a
bent/broken socket somewhere.  It's also possible that there's a short between
a couple of address lines on the video side, or even that the info being 
written to RAM by the processor is suffering from a shorted address line.  The
last is a bit unlikely, as it would probably affect other things (like,
preventing the MOS from running properly).

Pete