if you want to put zero values it's your call, for me it's a no, you could really have backlight problems and the ic may or could fry ??
even on the spear mcu there could be some backlight pin control / contrast ... output .... a simple bad solder could be a problem
To be sure
Try to supply the bakclight with an external current controlled psu if it lit's up and you see the meter display / digits etc .... if it is okay, the schematic show an serial parallel diode array on the 2x Isink pins, and the resistors does current limitations for the ic, it as 25 ma max output per rail, you could be in an overload situation ?
If not you have to follow this circuit, understand it / repair it
small story : i have dealt with lots of fakes ones recently, even huge fgpa's ... micro power ic's etc .... a nightmare, i have one 10x10 cm pcb who cost as much as the 34461a meter loll, has 11 supply lines in it for fpga, memory, i/o's and 1 huge (16 channels) supply supervisor ic, when this one decide to play with you .. you're up for the long run
For me changing twice an ic, is still possible : Simply overheating it, could have damaged it ...still unresolved issues around it .... many factors can or could happen, or happened ?? manupulation(s) etc ...
Brand new is not a garanty of resolving your problem, and sadly keysight is not helping
If other(s) have repaired the unit with zero values its their problems if it blows up again ... the circuit has been deisgned a certain way ... they would not put parts who serve / do nothing ??
And this ic has many supply lines, dont forget that some meters have problems reading the inductors voltages if it is on the ic side / frequency switching ... once it's filtered, you can read good values, you have to understand the topology used in this case, feedback lines, powergood, circuit biaising .... reset line, enable line
changing a part is sometime easy, sometimes not ..