Hello,

I took on a friend's Kenwood head unit (KDC-PS909) with the intention of
reparing it. It would power up correctly, ask for the security code (which I
have) and turn on but no audio. I cracked it open and noticed a chip,
TC7662, pretty hot Turns out, this is a DC-DC converter. Upon power-up, it
would output roughly -8VDC but soon drop off. Odd, I thought. There was also
a ground PCB track on the solder side that was toast. It's in the vicinity
of the DC-DC converter chip. I have a new chip coming to me in hopes that
that will fix it.

However, I've created a new problem. While waiting on this chip, I asked
myself, "where is the security code stored? Internal EEPROM, external?"
Then, I noticed an 8-pin chip sitting next to the NEC MCU marked KKZ01.
After a little research, it turns out that this is a 93C46 EEPROM.

Long story short, I removed the eeprom, put it in my programmer and
proceeded to dump the contents. I solder the chip back in and now I have NO
display whatsoever. So, if the chip was inadvertently written to, would this
cause the MCU to not display anything in an attempt to fool a would-be
thief?

I've also noticed that there's a transistor used as the +8VDC supply
(2SD2396). If I put my meter on it, power up the unit, it'll show about
+7.5VDC for maybe 11 seconds and bam, it dies out. I'm thinking is probably
related to the DC-DC chip not doing its thing. Although, it seems to be
under microprocessor control because if I reset the chip, it'll come back to
+7V and zero out after 11 seconds.

So, the only thing I'm after is a copy of the EEPROM's contents so I can
re-burn it. However, if a corrupt EEPROM won't prevent the unit from even
turning on, I'll pursue other avenues.

Thank You and Good Night,

-Tim