[miscend]

I've bought a brand new O2 amp. It works fine when connected to a power source. But the batteries are not charging and therefore I can't use it without a power source. However the 9v batteries do work when I remove them and charge them in a separate battery charger unit I own - which is not convenient!
 
Rather than sending it back to Switzerland for repairs, which will cost me money and incur a two week long wait. I've decided to take out my test probs and soldering kit. Does anyone where exactly I should be looking on the circuit for a solution the fault?

 

[Neccros]

Who made the O2?

 

[FallenAngel]

https://doc-0s-8g-docs.googleusercontent.com/docs/securesc/n9366alcipsk22g0834g8linptrss4mo/6isgj6rk48crr9tqq5relckp3fodsrsn/1460800800000/02744822904832082059/11052143009011523995/0B52Awjeyc5zKMjRlYjlhNGItNGJlNC00ODlmLWIwM2MtNDI4ZWU4YWRjY2Y4?e=download&nonce=una0m24ujp9pq&user=11052143009011523995&hash=bna3urpv08oee0tnsdvstgfo3bh9oiso
 
That's the documentation.
 
The power input and battery charging circuit is supper simple. Take a look that it's populated because it's optional. Maybe it just wasn't installed. There are barely any components, so it can't be hard to debug. Take a photo of the board if you get stuck.

 

[miscend]

There are no resistors on R2 and R1 on my board. Which is the power and charging circuit. Are those optional? It's made by headnhifi.

 

[MindsMirror]

That would be your problem. Those resistor's only function is to allow the AC supply to charge the batteries, so they are optional if you don't want that functionality.

 

[FallenAngel]

Luckily that's a $1, 1 minute job.