Electronics > Repair

Looking for Mettler Scale ROM backup

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fzabkar:
21 calibration parameters


--- Code: ---Offset(h) 00   02   04   06   08   0A   0C   0E

00000030                                     AEBA
00000040  0780 733C 04AE 02FF 3F05 055D FBA9 8EFF
00000050  FFF3 021A DC00 FF14 3C3E D6FD 000C F74B
00000060  CEFF 0000 072C 9A00
--- End code ---

Product ID


--- Code: ---Offset(h) 00   02   04   06   08   0A   0C   0E

00000000                                     4369
00000010  1937
--- End code ---

Model number PM200


--- Code: ---Offset(h) 00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F

00000000              20
--- End code ---

jamarjan:
Thanks for the response!
Unfortunately, it looks like my ROM wasn't damaged (it looks similar to yours).
After the swap, the scale still won't start.
For some reason, the microcontroller doesn't read the ROM's contents.
I have some activity on the NMC9346N read pin, but from what I can see on the oscilloscope, the instruction (read) doesn't seem to be correct.

All the voltages given in the service manual are within spec.
The microcontroller is warm but not hot.
The waveform on pin 1 uC doesn't appear every time the scale is started, and when it does, it has a strange waveform. I also have a not-so-nice XTAL2 waveform.
I'm running out of ideas on what else to check.
gmac34 I see that you know these scales quite well.
I, on the other hand, am an amateur hobbist with a very limited amount of electronic knowledge.
Maybe you have some tips for me?
Either way, you have a big beer from me ;-)

gmac34:
Well, it seems your scale is not starting at all, in fact I think the scale is supposed to do some self checks at power up, and should give you an error in case the EEPROM is bad. As a first step I would suggest you try to burn the UVPROM with the 10.45 version above and make sure your is not corrupted. Do you have an UV eraser? a bad Cristal could also be a suspect.

gmac34:
BTW, this was the behaviour of the scale I was trying to repair at the beginning of the tread, the UVPROM was corrupted, just a few stuck bits

I think we can safely assume the problem is in the digital section so either microcontroller, UVPROM, RAM or Cristal, I don't think IC1 can stop the thing starting

if you probed the Cristal correctly the waveform looks a bit wonky, so that could be easily replaced, next I would try the ram. I also assume that the analog part is working fine, do you see the beam move when you connect power? that part would work all the time, regardless of the state of the digital side

fzabkar:
Can you upload the service manual or provide a link to it?

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