Electronics > Repair
Looking for Mettler Scale ROM backup
<< < (4/11) > >>
gmac34:
Not a very useful SM
fzabkar:
I would check the data and address buses and the micro's reset pin.

Just out of curiosity, I notice that U4 (ME47820P) and U11/U13 (ME84202) appear to be Mettler custom parts. U4 has a crystal, so I'm wondering what it does.
fzabkar:
#jamarjan, your EEPROM is a 9346 (128 bytes), yet your dump is a 9306 (32 bytes). Why is that?
gmac34:
The other Cristal should be for the integrating ADC, ME47820P should be part of it, but not a integrated ADC ic, you see nearby a LM 393 comparator, Mettler unfortunately used a lot of parts with custom codes, but non necessary custom parts.

given the position of U11 I would imagine  it si just a precision op amps supporting the voltage reference, U13 is on the signal path coming from the measuring resistor, I know it can be replaced with a daughter board to adjust linearity, and that is all in the analog domain before the ADC.
gmac34:
this is a service manual for a Sartorius scale of the same era, I believe they are quite similar in their implementation, of the analog PID on one side the ADC in the middle and the microcontroller on the other.
unfortunately this is the only schematics I have for this type of scales.

IC106 in this schematics should be the counterpart of U4, it's a gate array, and has it's own oscillator
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