Device not turning on while directly connected to power

Hi all,

I've recently been asked to look at an iPhone 6 Plus after it had been repaired at a dodgy market repair shop.

The device had a wobbly home button, the battery looked swollen, the LCD stuck out of the frame extensively and the device would not boot. It would show the apple logo then just show black; the back light stayed on so the device did not power down. I narrowed this down to the device not being able to boot iOS and because of the faulty LCD no errors were being displayed.

I placed the home button back on the device correctly (as it was unscrewed when I found it!), popped the LCD back into place and removed the battery. Now I connected the device to a power source (again with the battery removed to see if there were any further issues). The device powered on, showed the Apple logo and went black again. I decided to take it home to flash it, hopefully to see if an error would display on the screen or if there were any other issues.

I've just plugged the device into separate forms of power. The first, my PC. No response on the LCD. Second, from a power port (plug). Both using a lighting cable that definitely worked. The LCD is plugged in correctly and I do not see any damage to the flexes under inspection, so I've turned here for some advice.

EDIT** Device is not detected by iTunes when attempted to switch it to recovery mode, furthering my suspicions that there is a power fault.

Thanks,

Ethan

TL:DR

- DEVICE WON'T POWER ON WHEN BATTERY REMOVED AND PLUGGED INTO DIRECT POWER SOURCE. EVEN THOUGH IT DID.

- DEVICE WAS PREVIOUSLY REPAIRED AT A DODGY STORE

- LCD IS FAKE, NOT OEM