When 6PA cover is off, USE PLASTIC TOOLS. Lots of exposed high power 28VDC.

1.How sure are we that we did not put the bad APU GCU in the number 1 position this spring(During APU Uncommanded Shutdown troubleshooting)? How sure are we that we did not put a bad EXCHANGE GCU in the #1 position.

2.Has 8P1 Been swapped? Tap on 8P1 while Generator is running.

3. Backpin GCU pin P. Watch this voltage while the generator is running. Should be ~27 VDC. fluctuating voltage would be a symptom of the failure.

4. A poor connection at Pin F of the GCU could cause the internal voltage regulation to fail. Check Pin Tension. Ring all the way out to Generator B lead

5.Visually inspect CR17, CR23 4.Remove CI1, Remove 6PA panel plug A and megger the leads on CR17, CR23

6.Remove 6PA panel plug A, and megger the Plug a Pin U to ground. Check the harness side going forward to the red switch.

Previous action:

Late June 2010: Happens on climb out prior to 10,000 feet.

Late June 2010: Performed A Lead megger check again. (New York)

Early June: CI1 and CI3(?) swapped (Switzerland)
HES 1 replaced with new. (Switzerland)
Another Circuit card swapped (Switzerland)

Late may 2010: replaced switch 2PA1 with new. (Bermuda) Mid spring 2010