So perhaps dig out win95 disc , make up the 7405 bridge, fire up iicuni and
from the Ezusb pdf ,fro

5.7 Serial EEPROM Present,FirstByte is 0xB0
Table 5-7. EEPROM Data Format for"B0"Load

0 0xB0
1 VendorID(VID)L
2 VendorID(VID)H
3 ProductID(PID)L
4 ProductID(PID)H
5 DeviceID(DID)L
6 DeviceID(DID)H
7 Notused

and
digital mixer VID 0B45 , PID_0001&MI_00
perhaps just loading hex version of
B0450B01000000 into the first 7 bytes instead of the current corrupted
087910B004BCC0.....

(I'm unsure about device ID at the moment)
is enough to start the ball rolling to do a firmware upload for the mixer