Inspired by your comment on the shorting of pin 50 to pin 49 I re-visited some tests I had done on rev 5.2 and setup a ‘torture test’ to see if I could re-create a way to make the rev 5.2 main power ECB fail (that is what you have by the way). We made a change for safety reasons to put the battery voltage that shows up on the 50 pin connector behind the main ECB. It seems now that this leads to this failure situation.
This applies ONLY to rev 5.2 and there is no need on rev 5.1 or 5.3 coming soon.
So I repeated some ‘torture tests’ and this time tried many times to do very fast shorts and long shorts and sure enough I was able to make the ECB fail after 15 or so tries.
We had changed this already for our rev 5.3 board but rev 5.2 has the very large R706 soldered down to the board. So for those people with rev 5.2 boards AND the ability to remove a large SMT resistor with a SMT rework heat gun here is my suggestion to avoid possible failures later due to unexpected shorting of the power on the 50 pin connector.
- With BATTERY COMPLETELY DISCONNECTED use an SMT heat gun to carefully remove the very large R706 that is located on the lower left of the board and is likely to be white with a ‘0’ on it. You must be careful to NOT remove very small SMT components right next to it so suggest pointing heat gun away from the tiny SMT components.
- If you do need the full voltage on the 50 pin connector (VERY FEW PEOPLE NEED IT) then Obtain a standard automotive 10 amp type ATC car fuse and install that in the two fuse clips on the back of the board very near pin 50 of the 50 pin connector which is called F701
There are other ways to do the effective removal of the effect of R706 which I only suggest if you are SAFE and good with an X-Acto knive or dremel tool diamond wheel cutter (one of my all time favorite PC mod tools FYI). If you have little to no experience in trace cutting, DO NOT TRY THIS FOR YOUR OWN SAFETY! An Exacto knive is VERY dangerous and use ‘boy scout’ cut away from your fingers if you go this route!
To Cut Trace: You will see a very fat topside trace that goes from R706 up the left edge of the board. If you cut this fat trace on the top of the PCB right above the ‘R’ in the white silkscreen of ‘Rev 5.2’ and be sure what you have done does NOT short this trace to the very nearby ground plane or cut much past the trace itself into the board that will do it.
A mod like this will possibly save you from a later failure if you accidentally short by dropping screw or something that shorts this battery power.
We are going to have this addressed on rev 5.3 boards hitting production very soon.