I am trying to repair a GPS unit. There was a zener diode (to56 PolyZen protection diode) which had blown off and I had replaced. This is part of the battery charging circuit I believe, as once I replaced it, the unit would power on and charged the battery for some time. Few weeks later the zener seemes like it has died again.
I found once I replace the zener again there is voltage at the battery terminal which slowly drops down but never comes back up so it seems something is killing it. The voltage drops gradually over 5 minuites
I’ve traced the output of the battery terminal to an IC like component that is next to this zener so have reason to believe it is faulty; but can’t figure out what it is.
The marking on the IC is D8 = 1K 70S
Would appreciate any insight as to what it could be.
It is the 10-Pin component in the middle, marked U750 on the board. The zener is slightly cut off the image next to C106.
Managed to find the component, it was RT9505GQW. Thanks to Remco Vink who pointed out the manufacturer was Ricktek. I emailed the company and got the correct part number. Many thanks to everyone for your help.
Hi I managed to replace the IC but didn't turn out to be the culprit. I keep getting 0.2v with the battery disconnected or battery voltage +0.2v when connected. I've found another component that is also connected directly to the battery and going to have a go at changing it. It is a 3 leg component with the marking "132V" situated next to the RT9505GQW I just replaced. Would really appreciate your help in finding this. Many thanks