Charger won't start TP4056

[kotylo]

Hi. Reaching out, maybe someone (probably PricelessToolkit) could shed a light on my issue.
I've soldered the PCB via Mini Hot Plate, which worked nicely. The reed switch also works and i get the 350-400m range on 868 antenna. What doesn't work is the charger circuit.

When i connect the power to the Type-C connector, the red LED flashes for like 50ms and stops. No current flows.

Measurements of TP4056 pins:

	TypeC ✔	Type-C ❌
Battery ✔	BAT: 4.06 Vcc: 5.08	BAT: 4.06 Vcc: 0.5V and dropping (after some time (sleep?) will be 0)
Baterry ❌	BAT: 2.0, and dropping.. now 1.01 Vcc: 5.08	BAT: 0.95, and dropping Vcc: 0.57 and dropping

I have tried to disconnect battery, but not Type-C and try to measure GND-Vcc, the Green LED did light up for a second and then faded away. Could reproduce it twice, but not anymore.

If i try to pull STDB pin low for a bit, the Green LED lights up faintly or sometimes fully, so it it not dead (yet :D)

Just tried to swap with different TP4056 chip from the same batch, same result, unfortunately.
Some photos:

[PricelessToolkit]

1. "When I connect the power to the Type-C connector, the red LED flashes for like 50ms and stops. No current flows." - It's OK if no battery
2. You can't power the MailBox sensor only with a USB
3. VCC for you is which pad?

I can't see any anomaly in this

	TypeC ✔	Type-C ❌
Battery ✔	BAT: 4.06 Vcc: 5.08	BAT: 4.06 Vcc: 0.5V and dropping (after some time (sleep?) will be 0)
Baterry ❌	BAT: 2.0, and dropping.. now 1.01 Vcc: 5.08	BAT: 0.95, and dropping Vcc: 0.57 and dropping

It's not charging ??

[kotylo]

Discharged to 3.9V, same thing :( Usually this chip will light up at least Green LED constantly if it's fully charged, so far i remember from other PCBs.

So i don't get this chip)))

• Vin 5V = ✔,
• TEMP pin is Grounded = temp sensing is disabled ✔
• No battery = there is a battery ✔

[PricelessToolkit]

It's strange! probably TP4056 is a dead "bad batch?" Maybe the last thing is "Clean pcb? there may be a short circuit under the resistors " I can't say anything else :( sorry, If you find the reason please let me know, I love such mystical problems.

[kotylo]

yeah, it calms me down that you can't find it) nice idea with short. I'll try those things and get back to you:

• transferring the working chip
• desolder resistors and check for shorts underneath (there was a bit more soldering paste that i wanted when i started, so it's a possibility)
• i have 4 more PCBs (of course), so i'll try them out too. But wanted to make sure i don't do the same mistake twice beforehand

[kotylo]

Find 2 differences... Thanks for idea to check for the short circtuit, lol :)

🤦🏻‍♂️

So i went with checking for resistor's values at first and one was "shorted". But when i desoldered it, surprise-surprise - there lies a path underneath by design! Could PCBWay have made a mistake? How is that even possible? Wh... did I do?! Omg... In spite of your nice BOM file, schematics, in spite of this beautiful design with white lines everywhere, i ef upd.

[PricelessToolkit]

It happens... #4 :) the first photo in this discussion "problem is visible very well" but I didn't notice either. the main thing is that the problem was found!