Understanding System Power supply IC: Help Needed

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Sir. The end has arrived.
I had time to work on this when my wife was away but now the time is not there.
Even though this will be my beach car in summer it is used as a commute vehicle by my wife for picking up stock to run a cafe. She has now demanded the non working unit be returned to its home as she does not like the gaping hole it leaves in the dashboard.

I will clip the connector and use it to connect an amp circuit for an aux input.

I half wanted this to work for your sake as you have been patient.
Thank you for your time and I have learnt a lot but the biggest lesson is... I have a lot to learn.

All the best and have a great festive season.
 
Finally been able to trace the ACC 12v a bit after getting a bit of light in the right direction and getting a photo to zoom in.
It went through the board a couple of times via holes but managed to get to this resistor.



Now I need to find out if this is correct output of the resistor for that IC next to it to be requiring.

You were so damn close! I had the exact same problem with my Matsushita radio. It turns out those shitty panasonic thick film resistors dividing the voltage from the Batt+ and Acc lines to the AD8065 comparator were intermittently bad. You got the wrong datasheet for our particular comparator which is what threw you off the trail. This is a special 8065 comparator specifically for Matsushita/Panasonic that detects voltage on the Batt+ and Acc on pins 1 and 2 respectively and outputs a high of 5v to the battery detect pin of the CPU. Pins 1 and 2 are supposed to read 1.2-1.9v with the key on.

I replaced all of those 2012 package resistors with medical grade thin film resistors and it turned right on. Specifically, R751(270k), R752(27k), R753(4.7k), and R754(47k). Here's a service manual of a similar radio PANASONIC CQ-LT1180TA TOYOTA Service Manual download, schematics, eeprom, repair info for electronics experts. The only difference is the "BA4900" power rail IC is updated to a more modern version. Otherwise it's exactly the same.
 
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