It's likely that your guesses are correct Franc.. you're far more
knowledgeable about these circuits.

I suspect that there is likely to be widespread damage from connecting to a
car battery with the polarity reversed.. surprising to me that there aren't
any obvious burnt parts to see.

It seems that Sony hasn't provided any circuit protection at all in the
VRD-MCn models, and when not using the original Sony PSU the user risks
causing damage.

The MC6 version is the latest model and is typically priced at about $200,
so a mistake can be costly.
I didn't contact Sony to see if a service manual is available, but that
would probably be the only way I could effectively troubleshoot these units.

--
Cheers,
WB
..............


"Franc Zabkar" wrote in message
...
On Thu, 7 Feb 2013 14:28:54 -0500, "Wild_Bill"
put finger to keyboard and composed:

D7 may not be across the DC supply, and not have anything to do with the
T3
failure.. that's up to the person testing the unit to determine.

I'm guessing that D7 is a Schottky diode. I suspect that D7, L4
(6.8uH) and U16 form a buck regulator that generates the +5V supply. I
can't see any reverse polarity protection on the PCB, so I would think
that U16 would have been hit.

The L2 and L3 coils are probably associated with U17 and U14 to form
their own +1.8V and +3.3V buck regulators. I suspect that each of
these ICs would have been hit also.

If I were the OP, I would locate the datasheets for the three ICs and
examine their application circuits, if any.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.