HP-50G Excessive Battery Drain / Fix?

[3298]

Just chiming in to report that I had this problem as well. In my case, the power-off consumption was 55mA, idle was around 65mA. For reference, the serial number starts with CNA 038, and the calculator came with firmware 2.15, which I have replaced with 2.15+HPGCC3. It worked fine for years, until I found it with batteries drained to <50mV each a few weeks ago. (I think that wasn't exactly healthy for the rechargeables I use.)
After having "fixed" a Casio Algebra FX 2.0 Plus in 2008 or 2009 (by re-soldering a flash pin, but a year later it broke again), I'm not afraid of opening up devices and did so with the 50G. I expected it to be harder than with the Casio (8 screws at the back, 4 of them inside the battery compartment, that's it), but my 50G turned out to be a lot more stubborn than the Youtube video linked in this thread made it look like. Still, I managed to pull the front and back halves apart without breaking them.
My knowledge about electronics was insufficient for finding the failed component myself, so I called in help from my father. Long story short, after working with magnifying glass and multimeter he pointed at a 6x3mm rectangle of black plastic next to the wires from the batteries. It had the writing "100" and "10P" on it; there are two of these, and the one he pointed at was a little closer to the display than the other one. (In these pictures they are yellowish, but still the largest boxes apart from the chips. The labels next to them are CT1 and CT9.) "That's a capacitor, and it looks suspicious." He took it out of the circuit, measured it again and said "Yes, that's it." He replaced it with another capacitor from his spare parts collection (the material and capacity didn't match, but he said that doesn't matter as much for what this capacitor is used for). Then we tested whether the 50G was working - yes, it was - and put the multimeter into current measurement mode - it showed 0.02mA! Very close to the lower bound of what it could show in that mode, but it was close enough to the 27µA reported here for an intact 50G, so we didn't switch it into µA mode and just put the calculator back together and called it a day.
In the end I have a fixed 50G, and no more dust behind the display cover - I took care of that while I had access, because why not.
Moral of the story: check those capacitors as well, not just the huge one next to the batteries and the diode D6. They seem to be able to cause this issue.

[andreitomaz]

Hello, I am Brazilian and I am also having trouble with these same problems in HP50G. Ioff=38uA, Ion(without calculating)=14mA. Use batteries Duracell lr03 and the calculator league after two days in the off state. I will try to open it and verifcar the capacitor and diode as discussed here. Excuse me but do not speak English, use a translator.

[brickviking]

(10-09-2015 12:32 PM)andreitomaz Wrote:  Hello, I am Brazilian and I am also having trouble with these same problems in HP50G. Ioff=38uA, Ion(without calculating)=14mA. Use batteries Duracell lr03 and the calculator league after two days in the off state. I will try to open it and verifcar the capacitor and diode as discussed here. Excuse me but do not speak English, use a translator.

Those are normal current values. Are the batteries dead? Did you replace the batteries with a brand new set?
Esses são valores correntes normais. As pilhas estāo mortos? Queria substituir as baterias com um novo conjunto?

(Post 41)

[Marcio]

Andrei, coloque pilhas novas, de preferência alcalinas, e verifique quanto tempo leva para esgotar. Sob uso agressivo, as pilhas de minha 50g não passam de 1 semana.

Caso ainda não tenha, sugiro instalar esse pequeno programa que faz as leituras de uso e consumo em tempo real do conjunto de pilhas AAA:

http://www.hpcalc.org/details.php?id=6587

Marcio

[andreitomaz]

(10-10-2015 02:38 AM)brickviking Wrote:  

(10-09-2015 12:32 PM)andreitomaz Wrote:  Hello, I am Brazilian and I am also having trouble with these same problems in HP50G. Ioff=38uA, Ion(without calculating)=14mA. Use batteries Duracell lr03 and the calculator league after two days in the off state. I will try to open it and verifcar the capacitor and diode as discussed here. Excuse me but do not speak English, use a translator.

Those are normal current values. Are the batteries dead? Did you replace the batteries with a brand new set?
Esses são valores correntes normais. As pilhas estāo mortos? Queria substituir as baterias com um novo conjunto?

(Post 41)

hello , I let the calculator in the off state , with the batteries inside. After 2 days ( without even making a calculation or even turn it on ) I can no longer turn it on. So I change the batteries , I try again and so I can turn it on. I left the old batteries " resting " for a while and put them back into the calculator, to my surprise the calculator called. It's weird, I do not know if it's problem with the power calculator or something else. I have two stacks of games: 4 rechargeable and alkaline Duracell 4 ( new ) .
Olá, eu deixo a calculadora em estado desligado, com as pilhas dentro. Após 2 dias (sem sequer fazer nem um cálculo nem ligá-la) não consigo mais ligá-la. Então eu troco as pilhas, tento novamente e assim consigo ligá-la. Deixei as pilhas usadas "descansando" por um tempo e coloquei elas novamente na calculadora, para a minha surpresa a calculadora ligou. É estranho, não sei se é problema com a alimentação da calculadora ou outra coisa. Tenho dois jogos de pilhas: 4 recarregáveis e 4 alcalinas da Duracell(novas).

[Marcio]

Depois que ela ligou, você chegou a medir a queda no sumo da beteria? Instale o programinha que passei e observe.

[andreitomaz]

Just measure the Duracell alkaline batteries with the multimeter . Voltage: 1.5V (OK) Current: 1.7A . I believe it to be no problems with current drain , although I think that is not normal calculator in the off state consuming a current 38microamperes .
Acabei de medir as pilhas alcalinas Duracell com o multímetro. Tensão: 1.5V(OK) Corrente: 1.7A. Acredito que não seja problemas com drenagem de corrente, apesar de eu achar que não é normal a calculadora em estado desligado consumir uma corrente de 38microamperes.

[andreitomaz]

(10-11-2015 02:02 PM)Marcio Wrote:  Depois que ela ligou, você chegou a medir a queda no sumo da beteria? Instale o programinha que passei e observe.

Marcio, instalei seu programa. Para os dois conjuntos de pilhas, a medição é boa. Para as Duracell aproximam-se do máximo, já as recarregáveis, ficam entre warning e good. Acredito que as medidas realmente conferem. Só não entendi a parte da "Bat Volt", a medida hexadecimal entre parentes seriam as horas? Esta medida varia muito.

[rizieri]

Hi. In the very first line of the display of my 50g, the one that also contains the arrows announcer, a symbol appeared between the alpha and the hourglass: it looks something like ((.)). What does it means? How to deactivate it? The calculator is using a lot of energy: around 4 new batteries every few days. Can the two facts be connected? Please take into account I work in a rather cold environment. Thanks in advance for your kindness.

RM Celli

[Voldemar]

(12-10-2023 07:47 PM)rizieri Wrote:  it looks something like ((.)). What does it means?

This is the low battery indicator. This icon is used for alarms too.

[rizieri]

(12-11-2023 05:09 PM)Voldemar Wrote:  

(12-10-2023 07:47 PM)rizieri Wrote:  it looks something like ((.)). What does it means?

This is the low battery indicator. This icon is used for alarms too.

Ok: thanks a lot. I supposed it were something about transmission …

Did nobody fix the problem of the high energy consumption?