MicroHacker Forum

I've got a new challenge. A NX with suddenly stops working. First, it looks like a straight forward RAM problem, but after opening the chassis i saw somebody else already replaced the chips with Hynix PC-RAMs. The owner told me, he bought the car as is 3 years ago. Well, i replaced them anyway but the unit still doesn't start

I got a similar problem a looong while ago where i was not able to recover the unit and so put it into my box of "issue to resolve in the future"

I think i start with measureing the various voltage regulator outputs and the UDROP signals around the power control which may keeps the OMAP from booting.

I'm sure you did it, but are you check all 12v, 5v and 3.3v lines? I have one FX with blown 3,3 regulator on desk last month

Thanks for advice, but yes, this is the very first thing i checked I have made a TP-List where to look at, to ensure all voltages are available, all power-logic is sattisfied and reset-logic is working.

I found that signal "PWR_RADIO_ON2" is missing. This signal is derived from an logic-AND gate out of "/PWR_UDROP_60" which is HIGH and "PWR_RADIO_ON" which is LOW and directly comes from the radio-processor (RU) UPD70F3283 port P11. This port stays low. The RU is also the one who takes the "/ONTIPPER" signal direclty from the power-knob into it's port P02, which is also an nonmaskable interrupt pin (NMI). The uPD could be draged out of deep sleep mode with that pin. Makes sense.

So it is this processor which controls the whole unit to startup or not, i guess. The question is why he does not allow the unit to start? Maybe it's broke, maybe it's internal flash is damaged? I will also try to replace the EEPROM. I know if the EEPROM is missing, the unit will also not startup.

No luck after EEPROM change. What i can measure out is that xtals are oszillating and /RU_RESET is high, so the uC should start. But i can't see any activity on the EEPROMs SPI data lines, they are all silent, whereas on a working system there is permanent flow.

So something is preventing the uC from boot/work.

There is a "V850_DEBUG" interface available on the red service sockets (Micromatch connectors) on the lower side of the board. Maybe this is a way to get aware if the V850 (uPD70F3283) is living or dead? Never done something with it, but i'm pretty shure there are programming/debugging tools for it available somewhere?

Besides of that, i will continue checking the IO-Signals. Maybe i try to desolder the chip and replace it with one i know it's working... i got that fine Jovy reworkstation, but with less experience right now. But maybe hotair is sufficient to get the chip removed.

I picked up another NX board with defective RAMs just to see if the RU is starting there, but it doesn't. So it seems that even if RU get's correct power and reset, it is waiting until the OMAP starts and fires it up by some communication, i guess.
So again it could also be that RU in my board to repair is ok, but OMAP has a problem.