Last month, we covered four steps and procedures for troubleshooting medical devices and systems in an easy-to-use format. These steps can provide a structure for the troubleshooting process and will serve as a guide to assist in the troubleshooting and repair of medical equipment.

This month, we will cover the next five steps that you can use in just about any order. The steps will vary, depending on the device, but make sure to use the three thought processes we covered last month when troubleshooting:

  • Look for the obvious.
  • Think simple.
  • Don’t overcomplicate the problem.

Also, as a reminder, before you start, safety always comes first when working on equipment, so make sure you know about any hazards associated with the device you are working on—whether electrical, mechanical, chemical, gas, or bacterial. Take all the precautions needed, including personal protection such as gloves, etc. When in doubt as to a hazard, assume it is present.

At this stage, you have progressed through the “look” steps (look at the device/product/process and look for the obvious) and have therefore covered much of what the next five steps suggest. You have checked the power cord, plug, switches, fuses, circuit breakers, etc, so if the unit does not “power up,” it indicates that there is a problem with the power supply, software, or system.

Rule 5: Does the Device Have Power?

Here we have the most common problem. Power is not just electricity; some devices require compressed gases, vacuum, or water to work. Are all of these required elements present and at the correct levels? This is the question that has to be answered. During the “look” step, you also would have checked on the obvious: Is it plugged in (both ends of the power cord)? Is the outlet “live”? Is the power cord good? Is there a second power switch on the unit? If the fuse is good, is the breaker open? These represent the most common questions and tests that you would perform. Other problems can be that the unit has a bad or missing battery that is part of the circuit and needs to be functioning for the device to work.

The signs that a device is powered up include indicator lamps, the screen is lit, you can hear a fan or motor running, and the pressure/flow indicators do not register zero. For pneumatic, hydraulic, or vacuum-powered units, do you hear or see leaks?

On some devices there is a voltage compensation switch, so check that to be sure it is in the correct setting. Also, some devices have a 50/60 Hertz switch that needs to be in the correct setting.

If the outward appearance is that power is present, recheck to see if the unit is now working before taking the covers off and testing the power. Be sure to test all functions and verify the output is what is expected.

On some networked devices, the main unit has to be powered for the “slaves” to work. This is not common but it can happen, especially in lab equipment, some ICU settings, and with some general IT systems.

Once the covers are off, you need to repeat step one very carefully, looking for loose connectors, connectors not in place, signs of heat, damaged components, etc. Look for the obvious, and think simple.

In most modern equipment, there is more than one power supply in an instrument, so you need to determine which of the power supplies is defective. They are often ±5, ±12, or 15-volt power supplies for the logic circuits, 60 to 120 volts for motors and certain displays, plus high-voltage power supplies up to 150,000 KV. Know what you are looking at before starting, because going across the wrong points with your meter could leave ashes in your hand or no indication of a voltage present. Remember, when testing voltages in an instrument ONLY USE ONE HAND.

It might not be cost-effective to repair the sub assembly or replace the defective component when located. Often, it is best to replace the sub assembly or board rather then go to the component level.

You manager needs to be involved with the call as to replace or repair. Remember that the price of the repair may be only a few dollars, but the cost of the repair can be thousands in lost billings for the hospital.


Three thought processes that will help you in finding solutions to service problems include looking for the obvious, thinking simply, and not overcomplicating the problem.

Rule 6: Is There an Input to the Device?

Here we come to a common failure point. Where does the input come from? This is the first question to ask. Is it a cable, electrode, probe, tissue sample, liquid sample? What, if anything, has changed on the input? If the device tests blood or tissue samples, are they properly prepared? Are the samples being presented correctly?

Additional questions and answers are needed for devices that acquire electrical signals from a source as the input of the device. As dumb as it may seem, is the patient alive? Has the patient’s condition changed? Has the patient’s temperature gone up or down? Is there more movement, such as shaking, shivering, thrashing around in the bed? Did an electrode or sensor fall off or its contact resistance go up? Are the lead wires and cable good? Did you do a self-test or calibration on the device? Is there an error message on the display? If so, correct that error first.

Return to Rule 2 and listen to the user. Sometimes they have the answer but are not sure of it, so they called you to confirm what they thought.

Rule 7: Is the Processor Working?

Although a rare failure point, this is where you can get into serious expenses if you do not handle this rule well. There are many options that one can select to determine that the problem with the device is in the processor. The first option, if present, is to do a self-test on the device. If that comes out OK, the problem is probably not in the processor. If the self-test comes back with an error code, then correct that before going any further. If the output is not accurate, there may be a processor problem—but the self-test should have picked up that problem. On some devices you cannot do a reset from the panel but have to do a full shutdown to reset the program that controls the processor. Check with the user before shutting down a device. If the output of the device is intermittent, check everything connected to the output before replacing the processor.

Rule 8: The Output

The output of a device is its final product. In many cases it is a delivered energy, a graph, or a set of alpha/numeric characters. In some cases it may be more than one.

Delivered energy can be light, such as laser; ultrasonic energy, such as therapeutic ultrasound; or high-frequency energy, such as electrosurgical. Fetal ultrasound may have two outputs: one to gather the data and the other to convert the data into an audio tone. Diagnostic ultrasound also has several outputs. From the transducers, energy is delivered to the target; the “bounce” of that energy is processed into visual outputs on videotape or in a picture. Other devices that have more than one output include fluoroscopic x-ray, MRI, and photometers.

The most common devices with graphs are recorders; ECG, EEG, and fetal heart rate are the most common of those. Problems with graphs often involve the paper not being installed correctly or the paper is not moving at a constant speed. Other problems involve dirt or wax buildup on the print head or stylus.

The alpha/numeric output can be on a CRT, printed on a sheet of paper, placed on a continuous roll paper, or sent via a network to another device. When the output of one device serves as the input of another device, there can be problems with the transmission of the data. Be sure to isolate the problem as either an output, an input, or communication problem.

Some devices will require specific test instruments to determine the output level of the device.

Rule 9: Memory or Program

This type of a fault generally affects both the processor and the output. Sometimes, it can confuse you as to exactly what the problem is.

With straight memory problems, the installed parameters may be wrong for the patient, they may be for another application of the device, or someone might be playing with the unit and has changed the default settings. It is a good idea to keep the default settings on a device on the inside cover of the service manual. If the default settings are changed on a permanent basis, that change should be logged into the same place, along with being entered into the equipment history.

Find Rules 1 through 4 in the January 2012 issue of 24×7.

Other devices may have a set number to procedures that it will perform, then it will automatically shut down until a new “program card” is installed. This can be the case with devices that are rented on a per use term or with reagent rentals.

What can be very dangerous is to have similar devices with different software levels. All devices of the same model number should have the same software level.

The last point that needs to be made is that you should develop a “book” on the devices that you commonly work on. It can be in your head, on paper, or in a computer database. Your memory and ability to use previous experience are critical to being a good troubleshooter.

David Harrington, PhD, is a health care consultant based in Medway, Mass, and a member of 24×7‘s editorial advisory board. For more information, contact .