The hash board consists of 104 BM1398 chips (silk screen sequence BM1-BM104) divided into 52 groups (domains), each group consisting of 2 ICs. The BM1398 chip used in the S19 Hydro hash board operates at 0.37V. Groups 52, 51, 50, 49, 48, 47, and 46 (7 groups in total), the 25V output by the boost circuit U9 supplies power to the LDO and outputs 1.8V. Group 45 to Group 1 are provided 1.8V by VDD 18V through LDO. Each time one domain is moved back, the domain voltage decreases by 0.37V. All 0.8V is provided by the 1.8V of this domain through the LDO output:
2. S19 Hydro hash board boost circuit:
The boost circuit converts the power from 19V to 25V.
3. S19 Hydro chip signal direction:
CLK signal flow direction: generated by Y1 and Y2 crystal oscillator 25M. Y1 is transmitted from BM1 chip to BM51 chip. Y2 is transmitted from the BM52 chip to the BM104 chip, and the voltage is about 0.9V.
TX (CI, CO) signal flow direction: from the 7th pin (3.3V) of the IO interface to the level conversion IC U2, and then transmitted from the BM1 chip to the BM104 chip. When the IO cable is not plugged in, the voltage in standby is 1.8V and the voltage in operation is 0.6V.
RX (RI, RO) signal flow direction: from BM104 chip to BM1 chip, back to pin 8 of the signal cable terminal via U1, and then back to the control board. The voltage is 0.3V when the IO cable is not plugged in, and the voltage is 1.8V during operation.
BO (BI, BO) signal flow direction: from BM1 chip to BM104 chip, measured by multimeter is 0V.
RST signal flow direction: from the 3rd pin of the IO interface to D2, R13, R14, and then transmitted from chip 01 to chip 104. When the IO cable is not plugged in, it is 0V in standby and 1.8V during operation.
Source: Antminer S19 Hydro Hash Board Repair Guide | Zeus Mining