HP 9845 C with 280 option startup failure

[Tony Duell]

> 
> 
> > 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.
> >
> >   
> Yes, it is the one in the boardswapper guide. In this special case, it 
> is a "complete assembly exchange" guide.

Yes, and I'm not sure why. The PSU in the Opt 200 machines (at least) is 
very modular, and it should be possible to isolate the faulty board with 
a few simple tests.

Amazingly the manual does give a strip-down procedure for the printhead. 
If you've never taken one of those apart, you should do so. The 
construction is very interesting.

> > 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.
> >
> >   
> The light pen itself is a fairly simple piece of hardware, but the 

Oh, OK, I wasn't clear. I meant the 'light pen option' -- that is the pen 
and the controller PCB. The pen itself is simple.

-tony