What was found
AIRCRAFT SKIN SHOCKS TO THE TOUCH BETWEEN RADOME AND FORWARD DOOR BOTH SIDES. REMOVED FROM SERVICE. PERFORM VISUAL INSPECT OF ALL STATIC DISCHARGERS PER E175 AMM 23-61-00-210-801-A. NO DEFECTS NOTED. DISCONNECT OF BATTERY PROBLEM STILL PERSIST. RECONNECT OF BATTERY. GROUNDED A/C PER E175 AMM 20-40-02 AT ALL GROUNDING POINT. REPLACED JETWAY GPU W/ MOBILE DIESEL CART & PROBLEM RESOLVED. REPEATED SHOCKING PHENOMENON SEVERAL TIMES & FOUND TO BE DIRECTLY RELATED TO JETWAY GPU. SHOCKING DOES NOT OCCUR WHILE A/C POWERED BY APU OR KNOWN GOOD GPU. NO FURTHER DEFECTS. AIRCRAFT RETURNED TO SERVICE.