1 Dec
2014
1 Dec
'14
6:02 a.m.
On 11/30/2014 11:53 PM, tony duell wrote:
Yes, I seem to recall that those were bad - but the corrosion had spread
quite far around the connectors. :-(
Unfortunately I don't seem to have any MG-1 photos here to compare it
against, and it's been 7 years since I've seen one. In the CG-200 the
memory boards sit along the left-hand edge of the system, and I think that
is true of the MG-1, but four of the primary nsxxxxx ICs live on a little
plug-in daughterboard - I have a feeling that wasn't the case with the MG-1
(its primary ICs lived in sockets directly on the motherboard), and hence
that it's a different animal.
The amount of RAM on the video board is 512KB, I think - which is an odd
number; not enough for an 8bpp version of the MG-1's 1024x800 display, and
yet rather high for a mono display (I think CRTs in the multi-megapixel
range likely existed then for specialist applications where money was no
object, but if someone had the cash to burn they'd probably be buying
something other than a Whitechapel). Of course maybe it outputs
1024x800 at 4bpp, but I thought that by the mid-80s serious colour-capable
hardware was generally outputting 8bpp minimum (and non-palettised outputs
were appearing on the scene).
While I can see a 6845 IC on the board in my photo, I can't make out what
the other large (28 pin) IC is on the board near to the video connector - I
suspect it's a DAC of some kind, but knowing exactly what might be useful.
cheers
Jules
On 11/30/2014 12:51 AM, tony duell wrote:
The main problem in my experience is corrosion of the (tin plated) Molex
KK connector between the power control/battery PCB and the motherboard
This carries the system power (!) and corrosion leads to all sorts of problems
due to the fact that the 5V line is anything but. It needs a good set of NiCd cells on the power
control board to start it up.
If not, you have to do a 'jumpstart' involving connecting a 9V battery to a
connector
on that board. Some owners added an external socket wired there to make it
easier to so this.
I think I've seen four of the machines in total; every single one of them
had suffered significant corrosion to the main PCB beneath because of the
batteries. That
particular system has an ISA serial board and some flavour of ISA
video board (whatever the latter is, it has 8x 41264 dual-port RAM chips,
and there's a 20-way ribbon cable attached which runs off somewhere beneath
the ISA adapter board). Unfortunately the machine - like the MG-1's - had
also suffered significant corrosion.
I wonder if that's the colour video output card. Does this CG200 have the normal
MG1 motherboard in it? I seem to remember a connector on the motherboard
that carried at least the video timing signals.