HP-50G Excessive Battery Drain / Fix?

[jebem]

(05-27-2015 04:48 PM)HrastProgrammer Wrote:  I measured the following:
Off ... 12mA
Idle ... 24mA
Work ... 65mA

Something is definitely wrong with this calculator because those Off/Idle values are too high ...

Yap, there is a serious issue there.

While I'm not able to supply a schematics, we know that these things uses a capacitor in parallel as well.

Besides the possible protecting diode most probable root cause (I don't know if there is such a protection device installed in the 50G), there is a much smaller possibility that the capacitor may present leaking.

To check for a normal power supply input impedance values:
- Using a wire to short positive and negative terminals in the battery compartment during at least 5 seconds to discharge the capacitor;
- Using a digital multimeter, selecting Ohms auto-range, negative probe to negative terminal and positive probe to positive terminal: initially the reading resistance is very low, but a few seconds later the reading should be above 5MOhm.
- Now, selecting voltage readings in the multimeter, we should read a positive voltage, typically around 0.4V and the value should not decrease with time.

Whatever is the cause, the major issue as I see it, is the fact that to open these machines we need to force the entry, as there are no fixing screws to allow hardware serviceability.
I would return the machine and ask for a refund.