820-2879: PPBUS_G3H drops slowly from 12.4 volts

[pauly341]

Greetings. I'm having this similar issue with multiple boards and I always end up chasing my tail - so wanted to start fresh before I started replacing stuff.

When the board is connected to AC only, PPBUS_G3H measures 12.4v but then starts decreasing by about 1 volt per second. No issue once battery is connected. On other boards, I've replaced u7000, u6990, multiple resistors and caps around these ICs but no luck. Should I be thinking about some other type of component failure such as a coil?

thanks,
Paul

 

[pauly341]

17/18 = 2.9 ohms
27/28 = 20.2 ohms

It does power on from a charged battery

discharged for about 4 hours

 

[dukefawks]

Does it charge the battery normally?

 

[pauly341]

It doesnt. Light stays green when batt is connected

 

[dukefawks]

In this case I would suspect Q7030/35 or U7000.

 

[dukefawks]

Did you check stable voltage on pin 2 of U7000? 5V on pins 19,20?