Your reader corrupted the chip. The system is infact designed this way to
avoid being tampered with. You can only have this re-programmed by the
authorized service rep for Kenwood radios. They infact do not support
outside service or any outside parts sales for their products. They will
tell you to send them the radio for service only. Otherwise, no parts...
--
Greetings,
Jerry Greenberg GLG Technologies GLG
=========================================
WebPage
http://www.zoom-one.com
Electronics
http://www.zoom-one.com/electron.htm
=========================================
"Tim H." wrote in message
news
iFob.56248$275.141733@attbi_s53...
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