HP9836C colour alignment (grey scale tracking)

[Roy J. Tellason]

On Friday 03 October 2008 14:41, Tony Duell wrote:
> [HP's odd designs]
>
> > Some engineer got very clever there,  it sounds like,  and then somebody
> > else in the hierarchy decided not to let you in on how that worked,  in
> > detail...
>
> That reminds me, in passing, of the HP98x0. The 'service manuals' are
> boardswapper guides with PSU schematics only. But HP patented the
> machines, and the patents (I have a list of the numbers, I think they're
> also on Eric Smith's site) are several hundred pages each, and include
> such interesting things as schematics (albeit of pre-production
> machines), interface schematics, the machine language instruction set,
> ROM sources (sysrem firmware and many of the expansion ROMs, etc). In
> other words what _should_ have been in the service manual...

They actually put ROM sources in the patent?  Wow.  I wouldn't have expected 
that.  What I would like,  if not stuff quite so detailed,  is something 
along the lines of "this is how it's supposed to act" for a lot of stuff out 
there.  Like all those VCRs that I encountered that simply wouldn't turn on, 
where I went looking for power supply and all sorts of other issues initially 
only to find that if the controller chip in there didn't get what it 
considered to be a sensible response from the mechanism when it tried to move 
things it would give up.  Causes were as simple as bad belts,  etc.

> [...]
>
> > > Over 10 years ago I bought an HP LogicDart. It was expensive, but I
> > > have never regretted it. I've got other instrumetns that do all it will
> > > do and more, but that's a useful handheld tool that will find 99% of
> > > digital faults in classic computers, if used with that most important
> > > piece of diagnostic equipment -- the thing inside your head.
> >
> > Yes...
>
> I will emphasise that again. The best tools/test equipment/CAD
> system/whatever are no use at all unless you think about what you are
> doing and use them intellegently.

I had the good fortune to have a teacher way back when who knew this stuff 
well,  and who taught me how to troubleshoot,  though some of that was late 
in coming to fruition.  :-)

> > > The 3rd-party suppliers over here will sell you a flyback for TV model
> > > <foo> or monitor <bar> but they don't give any more details than that.
> >
> > A generic replacement type flyback?  Or an OEM part?  If it's the former
> > then maybe there's some hope.
>
> They're not generic, in that they don't fit more than 1 types of
> TV/monitor, but they're not really OEM parts, in that I suspect the
> original flyback came from a different supplier. I suspect in some cases
> the original was reverse-engineered and said third-party company came up
> with a functional equivalent. It's only worth their while to do this if
> they are likely to sell many of them, of course, so the HP9836C is not
> going to be on the list...

Hmm.

> I must admit I've never had any success with these third-party flybacks.
> I had an Amstrad VGA monitor with flyback trouble (the voltage divider
> block for the focus and A1 supply was reaking down), 

Snap,  Crackle,  Pop!  :-)

> I ordered the so-called replacement and fortunately I checked out the
> winding connections before fitting it (that is, I checked which pins were
> connected by windings, which sets were totally isolated). I say
> fortunately, because if I'd fitted it, the 100V or so output from the 
> monitor's SMPUS would have been directly connected to the CRT heater!. In
> the end Iought the genuine Amstrad part (yes, it was available, it was
> also a lot more expensive) and had no prolems.

Interesting.  And yes,  I've encountered the occasoinal bad cross-reference 
too,  though thankfully they're not all that common.

-- 
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space,  a critter that can
be killed but can't be tamed.  --Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James 
M Dakin