HP98035 Real Time clock and AC5954N clock chip

[Curious Marc]

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