I have a V2 that won’t boot, no display, Draws 0.4 A and not in RCM mode. No shorts around M92T or BQ chips. Checking around M92, it’s missing the 3.3v on pin 6. I noticed on the BQ, SW pins measure 0.345v in diode mode. These pins lead to the bottom of the large coil. I believe they should measure 0.08v?
At one point, I noticed it displayed the low battery symbol and was drawing less than 0.18ish A. Once it jumped to 0.4 A, the screen was black. I replaced BQ and SW measured 0.08v and saw the low battery icon but then black screen. New BQ chip SW pins now measure 0.345v again so I’m very confused.
Thank you for the reply @Calvin. Yes, I used a mod chip but with no 3.3v, the chip isn’t powering on.
In checking the EN 3.3V regulator, I am getting VSYS from BQ but no 3.3v output. Thinking the regulator was bad, I replaced it but no joy. Interestingly, after replacing it, the mod chip did power on for 1 sec then off. Following the retrosix page, I injected 1v at the 3.3v output and it drawing >100 mA so seems I have a short on the rail somewhere. Checking around P13, my diode values are good, same with the fuel gauge. No shorts around M92t either.
Avoid that guide please it’s so dumb and leads beginners like you astray.
How to check if you have a short [to ground] on a rail? disconnect power and measure resistance to ground “injecting voltage” on a potentially shorted rail as the guide suggests is probably the most idiotic and roundabout things you can do, it’d be like me getting a scratch on my leg and amputating it to solve the problem again not yourt fault…stupid, stupid, stupid “wiki” / “guide” which has now led you down the garden path and muddied the waters.
If you were getting the charge indicator / low battery symbol then 3.3V was indeed present (at that point), so likely the console wasn’t prompted to boot prior to you checking for this rail or the rail is intermittent. A short on 3V3PDR would be typical in a modchip case. I’m guessing you’ve removed the modchip in it’s entirety while you diagnose?
@Severence Thank you for the reply. Nice to see you’re still active here.
Yes, I have removed the mod chip to troubleshoot.
I have measured resistance to group on the 3.3v rail in the following spots:
MAX77620H = 128 kohm
EN 3.3v output = 130 k
M92 = 132 k
P13 top cap = 127 k
So doesn’t appear to be a dead short to ground but I agree the rail is intermittent. Interesting case lol
Yep no shorts, all seem about right afaict, don’t think you ever had a problem with this rail as far as i can tell.
Next up, you can check the voltage following prompt to boot, you can use either the power button or connecting USB (might be a good idea to do both just incase you have a problem here) with the battery connected and then seeing if 3V3PDR is now present, if you still don’t measure 3.3V then i’d check the enable line to the ENXX IC and see if it’s high (ie. is the 3.3V output even being told to turn on)
Might be you no longer have an issue if you measure 3.3V following a prompt, and it’s emmc related problems which is the next most common thing in modchip scenarios
Following your help in this thread - tronicsfixforum. com/t/replacing-my-enxx-chip-but-the-pad-looks-messed-up-could-someone-look-at-these-photos/7170/19
Prompting to boot via usb, I am not getting the enable line to ENXX IC. Both sides of the resistor are 0v. So appears I don’t have 1v8 either. In that thread, the enable line comes from the SOC?
I suspected the Emmc initially but am able to read it so believe it’s good.
What voltage do you measure here following prompt? you might also wanna try prompting with the power button pads by shorting the the relevant point to ground either at the TP or at the power button flex connector (just incase you have an issue here, however unlikely that might be an issue)
Might also be worth measuring the other rails voltage on inductors surrounding the PMIC here too while your there.
When you replaced the ENXX IC, was it new preballed? from a legit source? (ie. not aliexpress)
This puzzling case just took an even stranger turn of events!
After leaving it for a few days I decided to check voltages. First I prompt it to boot by shorting at the power button connector and measured 4.2v for SYS but 0v for 1V8PDR.
Decided I might as well check the other voltages around the PMIC so prompted it to boot again and now get all the voltages!
Connect to the screen and the switch boots up fine. It suddenly just started working… no idea why or how. Guess I’ll monitor it and see if it lasts.
Sincerely thank you guys for your help! Will update if it stays working or not.
it’s so dumb and leads beginners like you astray.
“injecting voltage” on a potentially shorted rail as the guide suggests is probably the most idiotic and roundabout things you can do, it’d be like me getting a scratch on my leg and amputating it to solve the problem 
again not yourt fault…stupid, stupid, stupid “wiki” / “guide” which has now led you down the garden path and muddied the waters.