Hi, any repair guides for S7 boards showing the #48 asics? If im not wrong we have only the 54 chip version of the board. Thank you
There is essentially not a lot you can do without QFN rework facilities and understanding the board. If it's a chip fallen off situation (desoldered), you may be able to get away with a DIY fix, but even then it's not easy. Likely faults in high-temp environments on the 54 chip boards from what I've heard are:
Cap failure - which is not impossible to fix, the heatsinks on the back come off fairly easily.
Failure of the tiny boost converter which does the I/O voltages for the last (couple?) of sets of chips. Hard to fix unless you know what you're doing.
Failure of an ASIC (solder joint issue). Possible to flux and reflow, but cleaning without softening the adhesive holding all the rest of the heatsinks on is not fun.
Failure of an actual ASIC chip. Find the chip and replace. Not going to happen if you don't already do fine-pitch SMD work.
There is no PIC or voltage control on a 54 chip board.
I haven't seen a 54 chip board with black adhesive, but I don't have a large sample size.
You can get some diagnostic information by reading the voltages between each "set of 3" heatsinks - there should be around .666 volts per chip (some small amounts of variance is normal). However, even then, there's not a lot you can do without SMD rework.
Check the kernel log - I would expect to see timeouts because it can't see any of the chain - hence why it's defaulting to 48 or 30 chips.