Re: Totally OT, but I thought I'd ask anyway...

[Nama <forums6000@mac.com>]

On Jun 16, 6:01 pm, Alex Freed <alex_n...@mirrow.com> wrote:
> Nama wrote:
> > I believe there are three LS157's connected to two 2114 ram. This RAM
> > is then connected to the character ROM, which in-turn connects to the
> > video generator circuit.
>
> I take the DRAM statement back. I saw 3 rows of apparently DRAM chips
> and assumed this was all the memory. The 2114 is static memory, 1K by 4
> bits. Two chips make a kilobyte that is apparently used as separate text
> video memory. Pin 4 is A3 but the address lines do not HAVE to be used
> in order. So check the traces from pins 1-7, and 15-17.
>
> -Alex.

ALL FIXED!!! (well, not quite. I still need to figure out why I can't
load anything from tape)

Alex, you were absolutely correct. I probed all the pins around the A3
line and indeed some were low. I eventually found that a tiny (so tiny
in fact I couldn't clearly see it even with a magnifying glass) piece
of solder was shorting A3 to ground on one of the 2114 RAM.

Perfect diagnosis! I knew Apple II guys were the smartest retro geeks
around.

Thanks you very much for all your time.

Phil