As a technician you are confronted with a TTL circuit board containing dozens of IC chips. You have taken several readings at numerous IC chips, but the readings are inconclusive because of their erratic nature. Of the possible faults listed, select the one that most probably is causing the problem.

• A defective IC chip that is drawing excessive current from the power supply
• A solar bridge between the inputs on the first IC chip on the board
• An open input on the first IC chip on the board
• A defective output IC chip that has an internal open to Vcc