HP9836C colour alignment (grey scale tracking)
ard at p850ug1.demon.co.uk
Fri Oct 3 13:41:56 CDT 2008
[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...
> > 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.
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.
> > 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), 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.
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