Assuming there is a failure of some sort in the last stage pair, then the worst it can be is that the core has gone SC, if it was OC then nothing would be working. This will have pushed up the core voltage on the other chips slightly but only a small amount. Is the red led on that board still working?
Rich
Rich
I dont know what SC is, OC could be... overcurrent? Anyhow, it is hashing normally-ish (75gh/s loss), the red led seem dead. I never really paid attention before but right now its right blade's led does not seem to be on.
Whats the diagnostic, doctor?
Short Circuit, Open Circuit, referring to the chips being in a string from a power point of view. So if you have an OC chip none of them will work, if SC then the rest of the chain is powered at a slightly higher voltage so it might work, which yours is. The fact that the red led is not on means there is a fault in the IO (In Out
circuitry in one of the final pair of chips.Bottom line is that probably there is a fault in one of the final pair of chips, but that it is not preventing the rest of the chain from working. May not be a SC core, could just be a fault in the IO signal side of the chip.
However although I have a fair understanding of the circuit treat the above with a pinch of salt as so far I have not been able to repair my board with the last 4 chips not working....
Rich
So does a dead ASIC cause this or could it be like a bad resistor/capacitor ? Are there any guides on here where somebody successfully repaired their S5? I've reballed /replaced many IC before in the past, the BM1384 seems like it would be very simple to swap since its fairly large compared to most other mobile IC's i had to replace in the past.
There is not much to go wrong on each of the stages. A big decoupling capacitor , the level shifting components between the stages, and the 1.8V Low Drop Out regulator. A few measurements are needed to confirm that chip failure is the most likely problem, then just the job of robbing a replacement chip from another board.
As I said I have not yet successfully repaired mine and the next job on the list is to make an ASIC test jig so that I can check the chip I remove before using it as a replacement.
If I ever get this done I will write it up along with a trouble shooting guide. However at this point I feel that my knowledge is just in theory rather than practice.
I have found removing and replacing the chips difficult with the IR rework station I have. Because of the heatsinking effect from the copper areas on the board they need a lot of heat, and I am worried I am damaging the chips. I suspect I need a more expensive device than the one I am using
Rich
