australia
1st May, 2025, 11:02 AM
Hi,
A bike spent the winter in a barn, battery connected and went completely dry. Now recharged, engine fires up - but there's no response from the dashboard at all. Not a single sign of life.
On 'power on' the dashboard should perform self test, - fire up the LEDs and whatnot. None of that happens, not even a backlit.
They tend to get moisture. The very bottom of plate has some corrosion, but nothing critical. Fixed just a few input lines.
5YK-H3500
1086891
Disassembled, applied GND and 12V to both power supply pins:
1) 5V power supply L4949EP is OK. It goes to both MCUs and EEPROM.
2) MCU MB90F455. Power OK, crystal oscilates at 4mhz (scoped). This thingy seem to be over control of everything. Even all the LEDs are connected to its outputs.
3) EEPROM 24C04. Power OK. Upon startup a short burst on SCL (scoped) and much longer burst on SDA.
Manual tap on above MCU reset pin re-initiates the data read burst, so at least MCU is really trying to start up.
4) LCD screen driver PCF8562 does output some square signals, but the screen is blank.
Could it be that MCU receives somehow corrupted data from EEPROM and fails to start?
Any other hints what to look for?
A bike spent the winter in a barn, battery connected and went completely dry. Now recharged, engine fires up - but there's no response from the dashboard at all. Not a single sign of life.
On 'power on' the dashboard should perform self test, - fire up the LEDs and whatnot. None of that happens, not even a backlit.
They tend to get moisture. The very bottom of plate has some corrosion, but nothing critical. Fixed just a few input lines.
5YK-H3500
1086891
Disassembled, applied GND and 12V to both power supply pins:
1) 5V power supply L4949EP is OK. It goes to both MCUs and EEPROM.
2) MCU MB90F455. Power OK, crystal oscilates at 4mhz (scoped). This thingy seem to be over control of everything. Even all the LEDs are connected to its outputs.
3) EEPROM 24C04. Power OK. Upon startup a short burst on SCL (scoped) and much longer burst on SDA.
Manual tap on above MCU reset pin re-initiates the data read burst, so at least MCU is really trying to start up.
4) LCD screen driver PCF8562 does output some square signals, but the screen is blank.
Could it be that MCU receives somehow corrupted data from EEPROM and fails to start?
Any other hints what to look for?