JVC LT-24C681 (Vestel) Boot Loop Post Internet Connection Setup: Seeking Suggestions

I have a JVC LT-24C681 with a 15-second boot loop. I bought the TV used. The boot loop became apparent during setup. The vendor swears it was fine. The "Internet" said it was the PSU so I wasted £20!

Believing all Vestel 17MB11 boards were the same, I bought another one. My bad. It works but the picture's awful and upside down.

Taking the vendor at his word, and after reading some posts in this forum, I have a different theory.

The TV worked for a good couple of hours when I first switched it on. The boot loop only developed after I set up the Internet connection. I don't need the SMART features of the TV, but I can't get the TV to switch on long enough for me to change the settings.

Any ideas? Any suggestions?

Is the power supply in working order or maybe when it starts the network card, the voltage drops and that's why it reboots ?

Quote:

Думаючи, що всі плати Vestel 17MB11 однакові

Sorry, but you misspelled chassis. Maybe you have a 17MB110? And 17MB11 is a very old chassis.

My spelling's fine. I never wrote the word "chassis" - blame the translator.
Weird thing. Put the old board back in, the TV's been fine for 24 hours. I dare not go near the settings, but it is connected to my network. My PCs can see it.