Troubleshooting a Beolink 7000 with faulty backlight

I encountered another Beolink 7000 with the typical backlight failure, necessitating the replacement of the electroluminescent (EL) foil. However, this replacement did not resolve the issue. 


Subsequent measurement of the AC voltage supplied to the backlight revealed a reading of 0V, suggesting the presence of an alternative underlying problem.

No audible hum was to be heard from the inverter, and disassembling the device revealed signs of wear on the TR37 transistor (BC817), situated on PCB1. This wear may have resulted from stress-induced factors. The TR37 was replaced with a generic BC817 NPN transistor with the same specifications. The schematics and faulty transistor are shown below.



Applying power to the Beolink revealed that the issue had been successfully resolved and that the backlight was now working again.