'not well' Osborne 1 mk 2

From: Tony Duell <ard_at_p850ug1.demon.co.uk>
Date: Mon Jan 19 16:00:52 2004

>
> > And from where did this (magic) smoke come? You do, of course, realise
> > that it's smoke that makes electronic devices work -- when the smoke
> > comes out they stop working.
>
> Oh yes :) It was very weird - I've not come across conductive plastic
> before! I had the motherboard resting the right way up on the thick plastic

Presumably this is a conductive coating on the inside for RFI reduction.

> > If those _are_ the video RAMs, are you getting activity on their address
> > and data lines? In other words, is the video timing chain running.
>
> Haven't checked. I'll grab the data sheet for the 6116 and have a look.

The pinout is much the same as the 2716 EPROM, but with Write Enable/ on
pin 21. It's one of the pinouts that burnt into the permanent ROM of my
brain :-)

>
> > What, if anything, do you get on the screen?
>
> Garbage, but the same garbage every time I switch on, so it could be bad RAM

Well, in my experinece, static RAM tends to initialise to the same state
on each power-up. And if you're getting recognisable characters, it
implies the video timing chain, the chracter generator, etc, are all
working correctly.

So either there's some problem where the CPU can't write to video memory,
or more likely the CPU is not trying to write to video memory. Maybe a
RAM, ROM, or bus problem?

-tony
Received on Mon Jan 19 2004 - 16:00:52 GMT