OT: Argh--my old faithful HP16C is failing!

Tony Duell ard.p850ug1 at gmail.com
Sun Dec 3 00:32:20 CST 2017

On Sun, Dec 3, 2017 at 4:39 AM, Chuck Guzis via cctalk
<cctalk at classiccmp.org> wrote:
> On 12/02/2017 05:18 PM, Paul Berger via cctalk wrote:
>> A good source of replacement displays is from 12C of the same vintage,
>> there was lots of them produced and they can often be obtained for a
>> reasonable cost.  If you you look in the archives of the forums on
>> hpmuseum.org you will find advise on what to look for for a suitable
>> replacement.  I have done the surgery myself and it is not too difficult.
> That's good to know.   Yes, the ground seems to be littered with used
> 12Cs; I wasn't sure if the LCD was compatible.   I"ll do some reading.

I am pretty sure the orginal fault is the liquid crystal material leaking
out of the display. At rest the liquid crystal twists the plane of polarisation
of light through 90 degrees, when the electric field it applied then the
molecules line up and it doesn't twist the plane of polarisation. The
display has a polarising filter on each side, arranged at 90 degrees to
each other. So at rest light passes with no problems, when the
field is applied you are effectively looking through crossed polarisers
so it's dark.

Of course if the liquid crystal leaks out you are looking through
crossed polarisers with nothing between them so you get a black

The other Voyagers (10C, 11C, 12C, 15C) of the same vintage
should use the same display. But more recent 12Cs do not as
far as I know. You have to get one that uses 3 button cells, not
the version using a lithium cell.

There are at least 2 versions of the construction of the old
Voyagers. Initially the electronics was assembled on a
flexible PCB fitted to a plastic frame. The LCD was clamped
onto that. There was a tail on the flexible PCB that connected
to the keyboard (normal PCB heat-staked to the top case)
with a zebrastrip connector. Later on, it was all on one
PCB heat-staked to the top case. I've seen 16Cs of both
constructions and as far as I know the display are the
same. But if yours is the later version you will have to
cut the heat stakes to get the PCB out to replace the
display and re-attach it afterwards.


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