HP9836C colour alignment (grey scale tracking)

[Tony Duell]

[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.
> 
> 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. 

> > 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.

-tony