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SLUG seems to be dead after RAM upgrade

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  • ch.trinity
    Hi, after fattening the slug with 2 pieces of Micron MT48LC32M16A2 512Mbit SDRAM to 128MByte by replacing the original chips, my device doesn t boot anymore.
    Message 1 of 1 , Feb 25, 2008
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      Hi,

      after fattening the slug with 2 pieces of Micron MT48LC32M16A2
      512Mbit SDRAM to 128MByte by replacing the original chips, my device
      doesn't boot anymore. All four LEDs are dark, and on the serial
      console I don't see anything, even the really first + sign from
      redBoot. Via JTAG I'm able to read the flash memory, and I can see
      there is flash content mapped also to the address from 0x00000000, so
      it seems MEM_MAP flag in EXP_CNFG0 register still have the original
      after-reset value.

      I used hot air rework station and ESD protection to remove the
      original RAM chips. I soldered the new RAMs in under microscope,
      everything looks fine visually.

      Please answer my questions, and give me some additional hints how to
      continue the debug process.

      Q1: Does redBoot have any activity on the uart if there are no SDRAMs,
      or they are corrupted, etc...?
      Q2: Could it be possible to kill the PCB (e.g. killing some embedded
      via, etc...) by hot air?
      Q3: What is the exact location of the 4 resistors under the buzzer?
      I've blown them off with the hot air, and I don't know where to solder
      them back. I haven't found any picture with desoldered buzzer in the
      necessary resolution to identify the 4 resistors (822, 123, and
      2*103). However I think these are necessary only for the buzzer
      functionality, but who knows? (I've tried to figure out the
      configuration of them from the LM358's datasheet)
      Q4: Should peek, poke and readmem JTAG commands work properly also
      with registers? I was able to read out only crazy values e.g.: from
      EXP_CNFG0 or SDR_CONFIG.
      Q5: Is there any way to follow the boot sequence via JTAG? (I don't
      have any expensive debugger, only the free JTAG Tools 0.5.1.)

      Thanks in advance,
      T.
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