HP9836C colour alignment (grey scale tracking)

Tony Duell ard at p850ug1.demon.co.uk
Sun Sep 28 17:19:23 CDT 2008

> On Sunday 28 September 2008 13:20, Tony Duell wrote:
> > For those wondering what the current state of this monitor is, I've
> > cleaned up all the case parts and put it back together. It still works
> > (so I didn't do any damage taking it apart), although there are still red
> > fringes to the right of (say) white objects.
> If it were a convergence problem you'd see fringes of the opposite color 

Exactly.I've not looked carefully enough to see this (I think a magnifier 
is needed), but I don't think the complementary colour fringes are there, 
which implies to me that it's an amplifier problem.

> (cyan?) on the opposite side of the screen objects.  Since you don't mention 
> these I'm assuming that it's not the case.
> > I am not sure if this is a convergence problem or due to the change in video
> > amplifier response due to that open-circuit 12.4k resistor which I've not
> > replaced yet
> I'd change that out and go ahead and see what it looks like.

That's exactly what I intend to do. The video board was clearly intended 
to ahve 3 indetical amplifier circuits on it, the resistors in question 
should all be 12.4k. 

My experience is that if you find something wrong, it's best to correct 
it even if it appears to make things worse. 

> > (I wanted to make sure the monitor still worked after I'd finished pulling
> > it about before changing anything).
> Well,  I wouldn't worry too much about the beam current and all that stuff -- 
> change the resistor out and see what you end up with!



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