Philips Aquatec AT750

[najrao]

Uses a single 14430 Li ion cell, and should charge through the circuit provided (see pic), from 15V dc --- but doesn't. The cell itself checks out, holding over 650mAh happily. Applying the 15V input draws only <10mA, and the charging light blinks green, indicating charging. This goes on for ever, >8hours.
The IC 314PM01 cannot be traced, nor any schematic. Philips did not fit many components on this board, meant for higher end models I suppose. There are NO components on the back side.
Tracing the current path, etc., is difficult. Suggestions please, thank you.
 

[jpwm]

Where does the 15v DC come into the board and where is the battery connected? Tracing them would help to see which parts are part of the charging circuit. IC 314PM01 seems to be a little bit to big for a simple 1 cell charger. I had suspected U101, Q103 and the footprint in the middle to fit a generic charging and a battery protection circuit but they are not fully populated so they can't be the problem.

[najrao]

Thank you, jpwm.
The 15V dc gets in via a 2-pole connector, the pins of which are not visible but below the narrower left end of the pcb. See assembly picture below. As I said, it is difficult to trace which track goes where even as it is all on one side of the board. The bat negative does go directly to the negative charger pin, and there has to be a switcher to convert the 15V to the 4.2 or less required in the positive line. There is a L102, the giveaway. The user manual says it is but a slow charger, all of 8h from empty to full, so very low currents. Still, it has to cut out at 4.2V (the cell is devoid of any BMC). And the LED has to blink green all along while charging, and stop when full still showing green; change to orange when empty. There is also the single 1-pole push button to start and stop the motor, which needs some mosfets.
The 314pm01 needs to be delineated out. Perhaps all will be revealed.
Thank you for your interest.

[jpwm]

Hi,

The large IC seems to be an old NEC 8-bit Microcontroller
https://datasheetspdf.com/pdf-file/694316/NECElectronics/UPD78F9211/1
So if this chip controls charging and its dead, it might be impossible to repair. If everything  but the charging works you could fix it the not so clean way by soldering in an li ion charging module from china (you can get them for less than a dollar on aliexpress).

[najrao]

Yes, everything but the charging does work. There is no space for anything else: the pcb sits in close fitting watertight enclosure.
For now, and perhaps for always, I have drilled a 1.2mm hole to lead out the battery+ using a Teflon wire. This lets me charge using a bench PS.
I can only check the simpler components in situ.
Thanks, jpwm.