Reversed Polarity? 正負相反?

Dear all,

Something wrong with this Black Gate Cap. Notice that its polarity is reversed. I got a -ve DC reading when I measure it the right way and I got a Positive reading when I reverse the +ve and the -ve.

What could be wrong and what caused this?

各位大哥,

這隻Black Gate好過份. 正常方式去度, 佢出 -ve DC 7.2 Volt. 將正負相反, 佢出+ve 7.2V DC. 出咗什麼問題, 點會變成咁?

電容要電容表來測，你咁測好似係無意思。

Dear Accphoto,

I just want to check voltage, not capacitance wor ...

I also have capacitor meter ....

Forgot to mention.

The reson for posting this message is .... this capacitor has to keep the Polarity corrct. If I connect the +ve side to the -ve terminal by mistake, the cap will blow, right?

But from this Voltage measurement, it looks like the polarity of this cap is reversed! Is this a BAD cap now?

CAT

You cannot check voltage on a capacitor like this.........!
To check a capacitor , it is better to use a needle meter and see whether it will 放電 or not, otherwise,  Ido not know of anyway to check the "voltage" of the meter.

Dear Accphoto,

You mean using a Analog meter? And when you connect it to the meter, you should see the "needle" dropping as the capacitor is giving out "power".

I don't know ... how do I know whether a capacitor is charged or not if I don't have a analog meter? If I put my fingers across the lead of a charged capacitor, I may be shocked given the voltage is high enough.

What should I do with this cap? Is it dead? I used the same method (though it may be stupid) to test ALL other caps I have (> 30), their polarity stays just like what is marked on the shield. Just this one gives me an "opposite" charge.

If it is NOT dead, how do we explain the "reversed" polarity? Really confused me ... sigh

CAT

The voltage of the meter is reversed for analog meter. Red will give -Ve and Black for +Ve. I do not know electronic meter is reversed or not. So the charge and re-charge meter  will be reserved.

Dear Accphoto,

我都有一個電容錶. 我通常度 uf 數的方法是先用萬用錶 check 電容重有無電先. 聽講如果重有電的話, 度 uf 數是會不準的. 如果個電容重有電就先放電.

這次的問題就是由此而起. 我拆了十隻電容出來, 我要度一吓看看它們還 okay or not. 點知用萬用錶一度, 另外幾隻完全正常, 正是正, 負是負. uf 數也正常. 但這隻正負極相反唔在講, 連 uf 值也大大偏差. 因為這隻是正版 BlackGate, 所以先覺得奇怪. 是否在以前改機中不覺整死了它 .....

CAT

Yes, possible the capacitor was gone..... , i will check it whether it is open when connected to an analog meter.