grinding down chips was Re: QX10 graphics board - test-drb@ccmp.vtda.org

27 Jan 2006

so by your reckoning not all of the asics are readily
reproduceable. What about the gate array on the
graphics board (lets pretend there wasnt a primitive
ttl prototype to guide)? What about the 7220 itself?
Now something like that is bound to have loads of
docs.
--- cctech-bounces at classiccmp.org
<ard at p850ug1.demon.co.uk> wrote:
...
  > 
 > On 1/27/2006 at 11:33 AM Joe R. wrote:
 > 
 > >   Photograph it yes but a schematic is MUCH more involved since all dies
...
  > >have multiple layers. It's sort of like
trying to make a schematic of a
...
  > >multilayer circuit board when all you can see
is the top layer.
...
  > 
 > Ditto that--and recall that we're talking here about an old graphics
...
  > controller; no crypto and (relatively) very old
technology.  I'd rather
...

 If we're talking about the Epson QX10, then there's no problem at all.
...

 The later version of the board (which is what's in both my machines) 
...
  contaisn a 7220 (data sheet available), 16 RAMs, a
bit of TTL and an 
...
  Epson gate array. But the technical manual shows
schematics for that _and 
...
  for an earlier version_. That doesn't have the
gate array, it has more 
...
  TTL and a character generator EPROM.

 There must be some differences between the 'extra' TTL and the gate array 
...
  (IIRC there's a latch on a bus in one version
that's not in the other), 
...
  but they are sufficiently similar that you could
recreate a replacement 
...
  for the gate array based on the schematics in the
manual. The only thing 
...
  you wouldn't have is the exact font of the
character generator, but I am 
...
  sure you could create something that was readable.

 A bigger problem in maintaing the QX10 are the 2 hybrids in the SMPSU 
...
  (but IIRC part-scheamtics without component values
are in the manual) and 
...
  the 2 ASCIS on the floopy drive. And you'd have
probllems swapping out 
...
  the complete drive as this is a 1/3rd height unit
(not to mention the 
...
  fact that you'd want to keep the original one
since it's an interesting 
...
  voice-coil unit).

 -tony

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