Wow, so all the variations of ksger HW3.1 are very confusing. I have an older one and worked great, the black board with the switch regulator, and Davids fine firmware. I got 2 more and they have different boards, discussed a few posts back, got proper chips from digkey and started to get read to swap them. I was worried about the battery hooked to the chip to I removed it, without removing the display. Managed to get a solder bridge between the battery pins. This instantly smoked the diode into the V reg. Got desperate and removed the display, fixed the short, replaced the diode. I spend time looking at all the boards and schematics. And first I don't understand how shorting the battery pins could pull that much current. I get several hundred ohms from 3V3 to the battery. But fixing the short fixed the overload, was testing injecting 3V3 with a current limited power supply.
Looks to actually be named V20 Has anyone made a schematic? Is there a topic about this board somewhere? The crystal doesn't hook to the processor. There is a time data chip and it has a trickle charger function, maybe this blew. I guess that can all be removed from the board anyway. But I'm honestly about to start designing and building my own board. What would be the wish list for David's firmware. No RTC, crystal, or eprom? Then a proper voltage regulator and battery. What was the best board as far as the op amp for the temperature sensing? Any other advice? I've had several handles short and blow the mosfet, some circuit to shutdown the output would be nice if it was shorted.