6 Jun
2019
6 Jun
'19
8:44 p.m.
Thanks, I?ll see if I can find replacements. You can easily see how they get zapped: they
are 2.5V chips, the NiCd battery *is* the voltage regulator. Charging circuit is a simple
diode connected to 5V via a resistor. Battery dies, goes high impedance, somebody plugs it
in to try it out and poof! Clock chip gets zapped by 5V.
Marc
On Jun 6, 2019, at 8:24 PM, Tony Duell <ard.p850ug1
at gmail.com> wrote:
On Thu, Jun 6, 2019 at 8:57 PM CuriousMarc via cctalk
<cctalk at classiccmp.org> wrote:
All HP fans in general and Tony in particular,
I have the exact same problem. HP98035 real time clock module
(http://hpmuseum.net/display_item.php?hw=168), plugged into a HP9825T
(http://hpmuseum.net/display_item.php?hw=171), accepts commands, reads back
all 8's. Battery is new, is charging and at the correct voltage.
Documentation says "never run the module without the battery or it would
damage the AC5954N clock chip". When I got the module it had not battery in
it, so this is what could have happened. Tony, did you eventually repair
your module or find some data on the clock chip?
I've certainly got a working 98035, but I can't remember if I repaired this one.
The clock chip seems to be a normal digital watch/clock chip. The inputs to
it are essentially the 'set' buttons, the outputs are the 7 segment lines and
digit strobes. But I have not found a data sheet on it anywhere.
-tony