HP 33E Question - battery and NiCad batteries

[Eddie W. Shore]

I just ordered a new NiCad rechargeable battery for the 33E. When I plugged in the rechargeable battery and I used the AC adapter, the display goes haywire (cycles between all 8s, 1s, random symbol) for a few seconds before it blanks out.

Does that mean that the AC adapter is damaged or my battery needs to be charged?

Thanks.

Eddie

[Steve Simpkin]

(08-13-2021 12:25 AM)Eddie W. Shore Wrote:  I just ordered a new NiCad rechargeable battery for the 33E. When I plugged in the rechargeable battery and I used the AC adapter, the display goes haywire (cycles between all 8s, 1s, random symbol) for a few seconds before it blanks out.

Does that mean that the AC adapter is damaged or my battery needs to be charged?

Thanks.

Eddie

Try charging the batteries with an external battery charger. That will verify the batteries are fully charged (assuming the new batteries are good) and eliminate any potential issue with the HP charger. I wouldn't recommend charging the batteries in the calculator anyway as it's just too risky.

[rprosperi]

DO NOT plug the adapter into the 33E until you know for 100% sure that the battery pack is good and makes good contact with the unit.

Due to a crappy power supply design (which uses the battery pack to regulate the power from the charger) if the battery pack is not present (or not tightly connected), the charger can destroy the ACT chip and/or RAM chips. The symptoms you describe are exactly those seen when an ACT is damaged, however it is not 100% certain your 33E is damaged, some of them can 'freak out' like this without permanent damage.

Check the voltage of the battery pack, it should be about 2.4-2.6V. Of course, also verify the polarity (the terminal near the top of the unit is MINUS). If that's good, then make sure the battery makes proper contact with the 33E terminals. If so, the unit should turn on. If the connection isn't tight, try inserting something behind the far end to push the contacts tightly against the terminals. Foam, bunched-up heavy rubber bands, or even folded paper often work fine to wedge the contacts together.

Good luck!

[Eddie W. Shore]

(08-13-2021 12:44 AM)Steve Simpkin Wrote:  

(08-13-2021 12:25 AM)Eddie W. Shore Wrote:  I just ordered a new NiCad rechargeable battery for the 33E. When I plugged in the rechargeable battery and I used the AC adapter, the display goes haywire (cycles between all 8s, 1s, random symbol) for a few seconds before it blanks out.

Does that mean that the AC adapter is damaged or my battery needs to be charged?

Thanks.

Eddie

Try charging the batteries with an external battery charger. That will verify the batteries are fully charged (assuming the new batteries are good) and eliminate any potential issue with the HP charger. I wouldn't recommend charging the batteries in the calculator anyway as it's just too risky.

Any recommendations for battery chargers?

[Eddie W. Shore]

(08-13-2021 01:48 AM)rprosperi Wrote:  DO NOT plug the adapter into the 33E until you know for 100% sure that the battery pack is good and makes good contact with the unit.

Due to a crappy power supply design (which uses the battery pack to regulate the power from the charger) if the battery pack is not present (or not tightly connected), the charger can destroy the ACT chip and/or RAM chips. The symptoms you describe are exactly those seen when an ACT is damaged, however it is not 100% certain your 33E is damaged, some of them can 'freak out' like this without permanent damage.

Check the voltage of the battery pack, it should be about 2.4-2.6V. Of course, also verify the polarity (the terminal near the top of the unit is MINUS). If that's good, then make sure the battery makes proper contact with the 33E terminals. If so, the unit should turn on. If the connection isn't tight, try inserting something behind the far end to push the contacts tightly against the terminals. Foam, bunched-up heavy rubber bands, or even folded paper often work fine to wedge the contacts together.

Good luck!

Good news: The folded paper work and I was able to turn on the 33E with the NiCd batteries, without the AC adapter.

Bad news: one of the upper left segments is missing.
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I think one of the metal connectors (sorry I don't know what the technical name is) is missing. I am hoping I can get whatever is needed at a home repair store.

Pic: https://drive.google.com/file/d/1G9Mv_X8...sp=sharing

[teenix]

(08-13-2021 02:10 AM)Eddie W. Shore Wrote:  Good news: The folded paper work and I was able to turn on the 33E with the NiCd batteries, without the AC adapter.

Bad news: one of the upper left segments is missing.
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I think one of the metal connectors (sorry I don't know what the technical name is) is missing. I am hoping I can get whatever is needed at a home repair store.

Unfortunately, as all the similar LED segments are connected together inside the display module, it is more likely to be a dead LED segment. If it is then I don't think it is repairable. I do seem to remember that corrosion can get into these and someone on the web repaired one but I cannot remember the page.

cheers

Tony

[Steve Simpkin]

(08-13-2021 01:56 AM)Eddie W. Shore Wrote:  

(08-13-2021 12:44 AM)Steve Simpkin Wrote:  Try charging the batteries with an external battery charger. That will verify the batteries are fully charged (assuming the new batteries are good) and eliminate any potential issue with the HP charger. I wouldn't recommend charging the batteries in the calculator anyway as it's just too risky.

Any recommendations for battery chargers?

That question often devolves into a religious debate
I don't have any recommendations on a specific model. Just make sure it has a reasonably well established brand name and is rated for NiCads.

[BillBee]

Eddie,

For a charger I use a working 38e rather then risk my 33e. I really need to pick up the Cherry Box ala Waterhosko (The 'Bay) for external charging but until then that's how I charge the batteries.

-Bill