Odd 48GX failure mode (& 48 series?)

[mfleming]

Hi all,

I recently had an odd failure of a 48GX that used Eneloop batteries for power. When I tried using it for a little noodling around, I found it wouldn't turn on - the batteries were exhausted to the extent that one was reversed biased. The calc was fine the week before, but these rechargables tend to have a voltage cliff at the end of their useful charge rather than a slow droop in voltage that alkalines display.

I replaced the batteries but the 48 wouldn't turn on, it just shows a quick flash of the display the first try. After that, pressing the On button shows no response unless I first short the battery terminals before inserting the batteries back in. So I've tried Eneloops & alkalines, leaving the terminals shorted overnight, and leaving the batteries in overnight. Poking the reset hole beneath the lower foot, adjusting contrast, trying On-A-F, nothing seems to revive the patient.

This was a "for parts" purchase where I did the usual keyboard repair. The On key is not the problem though since the display does flash on briefly the first time I try the key with batteries newly installed.

I picked up a couple of 48SX models in the past couple of months that also don't turn on with new batteries and don't show the telltale keyboard connector issue. That leaves me wondering if there might be another failure mode that I'm not aware of. Perhaps something to do with the power supply or maybe an initialization failure that leaves the CPU in a halted state.

Has anyone experienced the same problem and know of the root cause of the problem? Any starting point would be helpful before opening this calc back up and probing around.

TIA,
~Mark
NB: I've replaced Eneloops with alkalines for the calcs I keep handy in case this might occur again. I only keep batteries in the models I use on an intermittent but regular basis.