HP9836C colour alignment (grey scale tracking)
Roy J. Tellason
rtellason at verizon.net
Fri Oct 3 20:13:05 CDT 2008
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...
> 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
More information about the cctalk