'not well' Osborne 1 mk 2

From: Witchy <witchy_at_binarydinosaurs.co.uk>
Date: Mon Jan 19 06:33:34 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
sheet (mylar?) that covers the bottom of the power supply and the underside
of the top part of the case, also plastic.

The magic smoke was bits of the plastic melting where it came into contact
with the RAM chips, so either the plastic is conductive or it just happens
to be that the 2 or 3 chips in contact with the plastic are dead and
overheating enough to melt it! Doesn't seem like it's done any physical
damage fortunately, and the screen still shows the same garbage it did

> > OK, so far we have +5V, clock signal and active address and
> data lines, or
> Did you check the other voltages at the RAM chips (-5V on pin 1, +12V on
> pin 8, +5V on pin 9, ground on pin 16)?

Yup, I was talking about the Z80 up there.

> 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.

> 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
or I suppose a bad ROM in that the CPU is trying to address the ROM and
clear the screen but it can't? It's actually an identical problem to my
TRS80 model 1.


www.binarydinosaurs.co.uk - possibly the UK's biggest online computer museum
www.snakebiteandblack.co.uk - ex-monthly gothic shenanigans :o(
Received on Mon Jan 19 2004 - 06:33:34 GMT

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