I've recently built a Mini3 and the amplifier section of it works great. I'm a little worried about the charging circuit though. I plug an 18V wall adaptor into the amp and the LED lights up fine, the wall adaptor is also the right polarity.
My concern is related to the voltage regulation. I plugged my wall adaptor in at 18V and the LED lit up. So I did the initial checks and found 13.32V across the battery terminals at 16.6mA. The output of my 7812 was 12V. I stupidly reversed the polarity of the wall adaptor and tried it backwards even though it was supposed to be centre positive. The LED didn't light up so I put it back to normal. Now when I check the voltage across the battery terminals according to the initial tests on the Mini3 site I get a reading of 16.82V and I have 16.6mA of current. The output pin of my 7812 is reading 16.85V and if I change the voltage of my wall adaptor the voltage out of the 7812 changes.
So I'm guessing I've fried the 7812, but I'm also thinking that wasn't the only problem as I was always getting a voltage reading far off 12V across the battery terminals.
So two questions, what could be wrong and am I still able to charge the battery using a higher voltage and just make sure I don't turn the amp on when it's plugged into the wall? It's the same current but even according to the readings I should be getting across those terminals the battery is being charged with a voltage higher than it's output voltage.
My concern is related to the voltage regulation. I plugged my wall adaptor in at 18V and the LED lit up. So I did the initial checks and found 13.32V across the battery terminals at 16.6mA. The output of my 7812 was 12V. I stupidly reversed the polarity of the wall adaptor and tried it backwards even though it was supposed to be centre positive. The LED didn't light up so I put it back to normal. Now when I check the voltage across the battery terminals according to the initial tests on the Mini3 site I get a reading of 16.82V and I have 16.6mA of current. The output pin of my 7812 is reading 16.85V and if I change the voltage of my wall adaptor the voltage out of the 7812 changes.
So I'm guessing I've fried the 7812, but I'm also thinking that wasn't the only problem as I was always getting a voltage reading far off 12V across the battery terminals.
So two questions, what could be wrong and am I still able to charge the battery using a higher voltage and just make sure I don't turn the amp on when it's plugged into the wall? It's the same current but even according to the readings I should be getting across those terminals the battery is being charged with a voltage higher than it's output voltage.
