HP 9845 C with 280 option startup failure

Tony Duell ard at p850ug1.demon.co.uk
Wed Nov 2 19:31:49 CST 2005


> >> There is another difference, the 9845C were shipped with colored=20
> >> functions keys ;-)
> >
> > What, all different colours, to indicate the colour that the text (or=20
> > whatever) will appear on the monitor? The HH Tiger did that.
> >
> 
> Exactly. Makes the C look a little bite more colorful.

RIght...

I assume, BTW, you've worked out how the 'keyswitches' on the 9845 work. 
It is possible to carefully dismantle one (or two, since the arrow keys 
are different) -- I had to do this when I was figuring out how the whole 
machine worked.

> 
> >> Thanks, I'm glad my PSU is still working. I've had enough trouble with=
> =20
> >> the 9845A PSU, which is only as half as complex, although the function=
> al=20
> >>    =20
> >
> > When you say 'half as somplex', do you mean it only has one main choppe=
> r=20
> > 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=
> =20
> > to the B or C. To the extent that both processor modules are on one PCB=
> ,=20
> > and there's a bus switching board alongside it.
> >  =20
> Yes and no. The mainboards connectors and the output voltages of the PSU=20
> are the same. Even the mechanical PSU assembly is the same, with the=20

Is this the PSU that's shown in the boardswapper manual? It doesn't give 
much detail (for some odd reason you replace the complete PSU, not just 
the faulty board...), but there are a couple of pictures of it.

> The color monitor has just enough space for one additional board, the=20
> light pen controller. Since I don't have the controller board, I=20
> currently don't care much about a light pen, although it would be nice=20

I don't have one either. It would be nice to find for completeness (if 
only to 'complete' the schematics), but....

It's clear the light pen was fairly hardware-intensive. Many of the video 
timing signals, including the outputs from the horizontal counter on the 
text PCB, go to the light pen controller.

> to see how it works. However I got a working graphics 9111A tablet,=20
> thats ok for now. Even a hopefully working 8"-floppy. So data transfer=20

A 9885? I have a few of those....

My 9845B came with a 3rd party mass storage ROM module. I am told this 
allows the use of HPIB disks (probably Amigo protocol). The main use of 
it so far has been due to the fact that it was a little PCB with normal 
chips on it, not an HP hybrid. Very useful for figuring out what the ROM 
module connections are.

> would be (theoretically) possible as well. When I get one of those=20
> &#$=A7*-9845 working.

> > they actually do there. I have now seen the HP boardwapper guide for th=
> e=20
> > monitor, but I couldn't easily work out the translation between my name=
> s=20
> > and HP's.
> >  =20
> 
> In case I  get a copy of the schematics,  I will try to help. Actually,=20

I've heard from Dave recently, he claims to have scanned said diagrams. 
Probaby time to pester him again :-)

-tony




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