These diodes ( 5 for each axis ) should prevent the voltage from going negative. 4 are for the wires to the motor, the 5th is on the power input for the driver chip. the 21ths diode is to protect the transistor that switches the relay
If only 4 are working, that means the others are "open" and won't do anything at all. Bad protection on the board.
I expect that the first problem did some more damage to the board ( parts on it ) which resulted in the fast subsequent dead of other driver chips.
As you can see in many articles on this forum, the TB6560 doesn't have a good reputation. It;s famous for problems. The chip itself isn't to bad, but it's sensitive to all around.
The higher current for the Y driver is hardly a reason for a higher failure chance. Most electronic parts die because of a ( very short ) over voltage or reverse voltage. They Flash through and it's finished.
The main chip will only draw a tiny bit of power when configured, but no motor connected. It will try to deliver the power until output voltage is at max, Nothing bad should happen as long as you don't connect anything when power is on.
If you can afford, have a look at separate drivers and a breakout board this will have much less chance that one failure will affect the other drivers.
The picture is the inside of my box, I use a CNC-USB MK2 card and 4 DQ542MA drivers running from a 36 Volt 9 A power supply stable for about 4 years This is connected to an old small PC not connected to the internet.
I take the files from my PC on a USB stick to this set.
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