1 Nov
2005
1 Nov
'05
12:22 p.m.
There is
another difference, the 9845C were shipped with colored
functions keys ;-)
What, all different colours, to indicate the colour that the text (or
whatever) will appear on the monitor? The HH Tiger did that.
Thanks,
I'm glad my PSU is still working. I've had enough trouble with
the 9845A PSU, which is only as half as complex, although the functional
When you say 'half as somplex', do you mean it only has one main chopper
circuit, not the 2 that are used in the 9845B Opt 200?
I have never seen a 9845A, but from what I've heard it's very different
to the B or C. To the extent that both processor modules are on one PCB,
and there's a bus switching board alongside it.
There are 2 expansion slots in the monitor. One is for
the lightpen
controller. THe other is for an arbitrary video expansion board. I have
neither option, so there are no schematics.
The color monitor has just enough space for one additional board, the
light pen controller. Since I don't have the controller board, I
currently don't care much about a light pen, although it would be nice
to see how it works. However I got a working graphics 9111A tablet,
thats ok for now. Even a hopefully working 8"-floppy. So data transfer
would be (theoretically) possible as well. When I get one of those
&#$?*-9845 working.
home-brew
startup fixure? I guess the only signals which are really
important are the NP and the NL signals. The first resets the address
registers of the alpha circuit and grabs the fist word from the crt
buffer in block 1, the other probably initiates another PPU bus
arbitration for grabbing one complete line of text from the crt buffer
in block 1. Maybe in absence of a crt the alpha circuit makes some kind
of continuous bus capture and the whole system hangs. And maybe the
mainframe can run even without crt when NP and NL are both pulled up to
logical 1. Two resistors would then be enough.
Another probably important signal is the HALT-signal, from which the PPU
knows it's the PPU and not the LPU, and which is generated by the alpha
circuit but probably triggered by the NP signal.
First problem (for you, at least). I drew all this out long before seeing
an HP manual, so I didn't use the HP names. And several of the signals
disappear into the PPU hybrid so it's almost impossible to work out what
they actually do there. I have now seen the HP boardwapper guide for the
monitor, but I couldn't easily work out the translation between my names
and HP's.