How to Troubleshoot a Tektronix 7903

Tektronix oscilloscopes are usually serviced by trained technicians. Though Tektronix has an extensive support page designed to answer user questions, the information online is often limited to basic use and troubleshooting. As an owner of a Tektronix oscilloscope, you have access to special support by registering your product. Additionally, Tektronix has a general troubleshooting guide for its oscilloscopes that is a useful guide for solving issues with your machine.

Instructions

• 1

  Look at the front panel. Tektronix recommends a seven-step logical sequence as a guide for basic troubleshooting. Check the control settings first, then check associated equipment, then make a visual check of the equipment, then look at the instrument's calibration, pinpoint the trouble and isolate it to certain blocks, check the voltages and wave forms and finally investigate individual components. According to Tektronix's troubleshooting guide, changing switch positions and observing the effects can isolate problems quickly. If a problem is consistent in all circuit positions, a larger problem is occurring.

• 2

  Identify the blocks of the oscilloscope. There are eight areas that may be causing problems, and isolating the issue begins with understanding the eight areas. These are the attenuator preamplifier and delay line driver, delay line, vertical output amplifier, trigger pick-off amplifier, trigger circuits, sweep generator, horizontal amplifier and CRT circuits. Beyond these eight main blocks, your oscilloscope contains vertical and horizontal deflection plates, a signal input and a power supply.

• 3

  Look for a power supply failure. The power supply controls all functions of the oscilloscope, and a failure here will result in an overall machine failure. Power on the machine. If nothing happens (no CRT power), check the power indicator. If it isn't lit, check both the line fuse and the Line Selector Switch. If none of these indicator lights are on, the fault is likely with the power supply.

• 4

  Isolate the problem. If the machine is powering up but no spot is displayed on-screen, adjust the vertical position control to try to move the displayed information to the center. Press the "Beamfinder" button to center the display. If there is no display after pressing this button, the source of the issue is probably the power supply, horizontal section or the CRT. However, if the beam moves up or down when pressing the button, the issue is likely the vertical section.

• 5

  Follow the manual for location-specific troubleshooting. Having identified the root of the problem, you can now troubleshoot in greater detail to locate the exact part causing a malfunction. If a user guide is unavailable, contact Tektronix for a replacement or consult the general troubleshooting guide (see Resources).