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.

[gwh]

Not helping much but I have a 48sx that showed similar symptom. I've now opened it but can't seem to be able to revive it.

I also had multiple occurrences of 48 only turning on with eneloop even though the alkalines in them were still good.

[Kiwi]

Hi Mark,

I don't know the root cause but I had similar problems with a couple of HP48's (S/SX and G/GX models) in the past. In some cases, leaving the HP48 without batteries for more than 24h and then putting back (brand new) A-brand alkaline batteries revived them for some reason.

It's worth a try.

[mfleming]

Certainly worth a try. I'm making do for now with a GX that requires a display press when turning on or off. Not too annoying

[Allen]

Any improvement if you use a paper clip to reset it under the foot?

[mfleming]

(12-03-2023 04:34 PM)Allen Wrote:  Any improvement if you use a paper clip to reset it under the foot?

Tried that, no dice. Just giving up on a fine model seems wicked

[johnb]

(12-03-2023 09:06 PM)mfleming Wrote:  

(12-03-2023 04:34 PM)Allen Wrote:  Any improvement if you use a paper clip to reset it under the foot?

Tried that, no dice. Just giving up on a fine model seems wicked

Did you check the other foot?

I recently bought a "non-working, but cosmetically new in box" 48s.
Under the upper left foot there was a reset hole, but it did nothing.
The "real" reset hole was under the upper right foot, and was marked with an "R".

[mfleming]

(12-04-2023 07:59 PM)johnb Wrote:  Did you check the other foot?

I recently bought a "non-working, but cosmetically new in box" 48s.
Under the upper left foot there was a reset hole, but it did nothing.
The "real" reset hole was under the upper right foot, and was marked with an "R".

Well, I thought the reset was under the lower right foot, but upper foot is correct. I could feel the button closing.

Alas, no joy in Mudville