BTC Troubleshooting & Repair 3 — Questions and Answers
Question 1: An ECG machine produces a wandering baseline on all leads. Motion artifact has been ruled out. What is the most likely cause?
- Poor electrode gel contact (Correct answer)
- 60 Hz AC interference
- Defective thermal print head
- Broken patient cable lead wire
Correct answer: Poor electrode gel contact
Inadequate electrode-to-skin contact caused by dried or insufficient gel introduces impedance imbalance, producing a wandering baseline.
Question 2: Which safety test measures the current that flows from the device chassis to ground under normal operating conditions?
- Dielectric strength test
- Equipment leakage current test (Correct answer)
- Ground bond impedance test
- Insulation resistance test
Correct answer: Equipment leakage current test
The equipment leakage current test measures chassis-to-ground current to ensure it remains within safe limits per IEC/AAMI standards.
Question 3: A portable suction unit motor runs but produces no suction. What should be inspected first?
- Motor brushes and commutator
- Collection canister lid gasket and tubing connections (Correct answer)
- Electrical fuse
- Motor speed control board
Correct answer: Collection canister lid gasket and tubing connections
A failed canister gasket or loose tubing connection breaks the vacuum seal, eliminating suction even with a fully functional motor.
Question 4: A blood pressure monitor (NIBP) fails to deflate the cuff after inflation. Which component is most likely faulty?
- Pump motor
- Pressure transducer
- Deflation valve or its control circuit (Correct answer)
- Cuff bladder
Correct answer: Deflation valve or its control circuit
The deflation valve controls cuff pressure release; a stuck-closed valve or driver circuit failure prevents deflation.
Question 5: When troubleshooting a medical device, the technician finds a leaking electrolytic capacitor on the power supply board. What is the correct repair action?
- Clean the board and continue using it
- Replace only the capacitor with an identical-spec part (Correct answer)
- Replace the entire power supply
- Resolder the capacitor leads and retest
Correct answer: Replace only the capacitor with an identical-spec part
A leaking electrolytic capacitor must be replaced with an identical-specification part; resoldering or cleaning does not restore its electrical characteristics.
Question 6: After replacing a fuse in a medical device, the new fuse blows immediately upon power-up. What does this indicate?
- The replacement fuse has a lower current rating
- A hard fault (short circuit) exists in the device (Correct answer)
- The line voltage is too high
- The fuse holder is oxidized
Correct answer: A hard fault (short circuit) exists in the device
Immediate fuse failure upon power-up indicates a hard short circuit that draws current far exceeding the fuse rating before the device can initialize.
Question 7: A hospital-grade power strip (HGPS) fails the ground continuity test. What is the maximum allowable resistance between the ground pin and a device chassis per NFPA 99?
- 0.5 ohm (Correct answer)
- 0.1 ohm
- 1.0 ohm
- 2.0 ohms
Correct answer: 0.5 ohm
NFPA 99 specifies that ground path resistance in patient-care areas must not exceed 0.5 ohm to ensure effective fault current conduction.
BTC Troubleshooting & Repair 3
An ECG machine produces a wandering baseline on all leads.
Motion artifact has been ruled out.
What is the most likely cause?