zero will not start once screen is connected?

[Lpoolm]

so i was almost finished on my new build, had an external usb issue and now its gone down hill from there....

i plug my screen (with 5v mod) direct to pi and power on all ok screen works, so rebuilt it all up and the screen flickers on for 2 seconds than off and pi reboots over and over?
i took everything off the powerstrip and just connected the pi and it boots, than i connect the screen with the pi and it goes on/off?

it worked fine this morning now nothing. i am out out of ideas?

any tips please..

[dryja123]

Possible ground fault. I had an issue where the physical external USB adaptor had a faulty ground pin and it did the same thing yours is doing. My soldering was solid but the USB was defective. Try disconnecting the USB and see if it isolates the issue.

Good luck

[oliddell]

I solved this by connecting battery in the circuit. I'm using a banggood power boost with cambles safe shutdown. Without the battery screen won't turn on as soon as battery is connected everything works.

[Lpoolm]

right i am really stumped now!

so i have my powerboost wired to switch and charging port on backide of case with two wires going across to a powerstrip, all i have connected to this is screen and pi, nothing else. when one or the other connected they work when both connected they turn on/off.
it made me think was the screen not getting enough power going to the power strip so wired the screen direct to +/- on pi with also two wires from them going to the powerstrip to power the pi.
i turned it on and it booted all the way to retropie, as i thought i sorted it it went off and rebooted? than each time after that it would boot for a few seconds then orange/green light on powerboost would flicker and go off and reboot?
is the pi pulling too much power, or the screen? i have also tried with a battery connected too and it is the same results!
i am stumped!

[Lpoolm]

just to update incase others have an issue, with just the screen and pi connected i took switch and usb charging port off and plugged power direct to the powerboost and it worked and stayed on?
i swapped the switch and charging port and plugged back in and didnt work? i swapped pi, same issue, i swapped the powerboost, same issue, i changed wires, same issue.
last option was to try another screen this seems to be ok? so now going to rebuild up for the million time...

[joeygbsn]

Have you tried using a DMM to test voltage or continuity or anything? Also testing resistance between points rather than continuity could shed some light on the problem. There should be very little resistance between connected points. Some close up pictures of your wiring may help others spot a problem as well. If it was me I would try one component at a time and test with meter to make sure all voltage levels make sense. Then start doing combinations of components while testing everything with the meter. Also what is your battery situation? The pi starting up and then restarting could just be as simple as a dead battery. To test this you could measure the voltage of the battery with nothing connected and note the voltage(should be around 4 volts for a fully charged battery). Then measure the voltage of the battery with everything connected and turned on. If the battery voltage drops a lot when turned on this could indicate either a discharged battery or a bad battery all together.

[marketus]

How many time to charge full the battery?