Avalon 921 hash board repair guide

Avalon 921 hash board repair manual

Preparation for repair:

Maintenance process：

1. Visual inspection：

(1) Check whether the soldering of the components on the A921 hash board is weak soldering or whether they are soldered perfectly, and whether the pins of the LDO chip are corroded or weak soldering.

(2) Check whether the pins of the array resistance are corroded or soldered perfectly.

2. Fault A: The specific chip number reported by the single board test

After the test fixture completes the detection, the serial port software will give the specific code of the faulty chip. During maintenance, only the chip corresponding to the code needs to be replaced.

Note: The BIN number of the chip used for replacement should correspond to the BIN number marked on the back of the hash board.

3. Fault B: The single board test chip reports 0

If the report shows “ asic count = 0 “. You need do the following things.

First, test the ground value and voltage of the main powering on the hash board. For standard values, refer to the table below. If there is a short circuit, it is necessary to check whether the corresponding circuit is burned or there is a problem of soldering. After the ground value test is completed, it is necessary to conduct a power-on test to test the voltage of all the powering units on the hash board. The test position and the value of the tested voltage can refer to the table below:

Second, test the main chip on the hash board if there is no problem with the voltage. The hash board of Avalon 921 is composed of 26 groups of domains connected in series, each group of domains is composed of a single chip, and each chip includes three powerings and four groups of signals. The three powerings are: Vcore, VTOP, and VDDIO, and the four sets of signals are: CLKin, Cin, Rin, Din and CLKout, Cout, Rout and Dout. As shown below:

Voltage test: each group of domains is composed of three chips connected in parallel, the VDDIO and VTOP of each group of chips are powered by 1.8V-LDO and 0.8V-LDO respectively, and there are test points for VDDIO and VTOP next to each group of chips for voltage testing You can test the voltage at this point. 

Signal test: The signals of the chips on the hash board are connected in series, and the signals of each chip are CLK, C, R, and D. It is necessary to test whether each chip has an output signal. The oscilloscope is mainly used to test the CLK signal, and the corresponding waveform is shown in the figure below:

Notice：

1. Because the chip modules are connected in series, the signal is transmitted from the 25th chip module to the 0th chip module, and it is necessary to check from the 25th chip to the 0th chip. If the last chip does not work, the subsequent chips will not work, which will cause the test fixture to show that all chips cannot be found.

2. If all the power supply circuit voltages and chip signals are normal after the hash board is repaired, but the hash rate cannot reach the original hash rate after the miner is started.You can change the control board or use the USB programmer to rewrite the EPPROM chip of the control board, and the hash rate will be normal.

3. For similar failures of the hash board of Avalon 9 series miners, you can refer to the 921 hash board maintenance process. Their principles are the same.