Devo7E voltage missing problem

I changed mcu to 256 and used 4 in 1 module replaced the orginal cyrf6936, also added a 2W power amplifier, it works some days. Then I add aux4 and aux5, to the devo7E, but when I power on, the devo7E show "battery too low, can't save and edit" or something like that. the voltage is dropped to 2v, 1.5v, and even lower to "-.- -v" The voltage is missing. I checked the batteries are fine at 6v. I remove the 2W power amplifier, the aux4, aux5 but the problem is same. Any clue what's broken?

Check C4 pin of the CPU, (ADC) it is connected to resistor divider measuring the Tx voltage.

Fernandez wrote: Check C4 pin of the CPU, (ADC) it is connected to resistor divider measuring the Tx voltage.

Can you tell me more where the C4 pin of the CPU is? Are you saying mcu? I search the pin map of the mcu and got this post www.deviationtx.com/forum/6-general-disc...-devo-7e-mcu-pin-map
Is it the left side of mcu PC4(ADC_IN_14) Battery Voltage one?

I re-solder the west part of the mcu, the voltage shows normal again, showing 5.81-5.95v when batteries are 6v. But after I put in the 2W power amplifier, the voltage show strangely drop to 4v, then goes up to 9v+. After I take out the 2W power amplifier, the voltage still keep showing at 9v+, even my batteries are 6v. If I want to drain large current from devo7E, where should I take? Strangely if I use the hot air gun blow hot air to the mcu, the voltage show normal back to 5.8v-5.95v. I suspect I pour too much pcb wash water at the pcb near the mcu to clean the soldering paste but it should dried long time ago, so wonder what's going on?

if you power the 2watt amp from the 3v3 stock circuitry, quite likely it is damaged now.

Even powering a100mW module, the Vreg get very hot, I took it our and put a pololu step updown. Search the forum.

The 2W power amplifier input 5v but with a stepup/down inside so can input 3-15v, drained from the A, B point, about 5.55 to 5.585v there when the batteries is 6v.
Anyway, after I turn on the devo7E some more minutes (15min), it shows up to 9v+, it is 100% sure bad now.

5V regulator is probably toasted. On devo 7e it's only rated at 100mA if i remember right. Anyhow after you replace that, you need to power the amplifier straight from the battery. Use a tranzistor between as a switch.

Edit: it might not be the 5v regulator. There is a 7e power supply schematic somewhere on the forum, it should be easier to troubleshoot what is wrong.

The Devo7E seems normal now, I fixed it by using hot air gun blow hot air to the mcu and other pcb area. The cause of the problem probably is the pcb wash water not dry enough at pcb or mcu, effecting the senor or resistor, or somewhere "half-soldering". Now the 2W power amplifier drain power from Devo7E normally.