Tools Required
J 39916-A CD and Cassette Diagnostic Kit
Important: Always compare the front speakers to each other, and the rear speakers to each other. Do not compare the front speakers to the rear speakers because the speakers may be different or their mounting environment could cause them to sound different.
The tones are used to test and evaluate coaxial speakers or other complex speaker systems. The following three basic tones are used:
The diagnostic tape in J 39916-A contains a section of tones for the purpose of testing and evaluating the system operation of a coaxial speaker or other complex speakers. The following three basic tones are used for this test:
| • | The 50-Hz sine tone |
| • | The 500-Hz warble tone |
| • | The 9-kHz spectral tone |
The combination tone is a blend of the three tones.
Bass/Sub-Woofer Test (50-Hz Sine Tone)
The 50-Hz sine tone evaluates the bass response of an audio system. This tone is also helpful in evaluating audio systems which have separate sub-woofer amplifiers and speakers.
Midrange Speaker Test (500-Hz Warble Tone)
The 500-Hz warble tone evaluates the midrange speaker response. At midrange frequencies use this warble tone rather than a sine tone. The location of a warble tone source, such as a speaker, is easier to identify. A normal sine tone can set up a standing wave within a vehicle. A standing wave may cause difficulties in determining the source location.
Tweeter Test (9-kHz Spectral Tone)
The 9-kHz spectral tone evaluates the tweeter or high frequency. The tone is a section of frequencies of equal amplitudes ranging from 8.5-9.5 kHz. The sound is similar to crickets chirping.
This type of tone is used for the following reasons:
| • | Much like the warble tone, the source is easy to locate. |
| • | The spectral tone is easier to identify for those people with high end hearing loss problems. |
All Speaker Test
The combination tone may be used for numerous audio problems, such as distorted sound or no sound from the affected speaker. When using the combination tone, make comparative AC voltage measurements on the speaker terminals, ensuring that the fade and balance controls are in the detent position. With these voltage measurements, make a determination in the diagnosis of a speaker or amplifier.
Speaker/Grill Rattle Test (50 Hz to 8 kHz Swept Sine)
A portion of the tape diagnoses speaker and grille rattles. The first test is two tones played back-to-back. The second test is a variable frequency tone, but the frequency change is at a much slower rate. Use either of these tests in order to repair a speaker rattle or buzz. When you have isolated the problem, set the fade and the balance controls to the proper location. Then play the test tones in the specific problem area.
Motor Speed Test
A two-minute time period is marked in this section of tape which tests the cassette tape motor speed. Use this portion of the diagnostic tape in order to verify conditions of abnormal sound from the cassette tape player. In some cases, improper tape motor speed may cause audio abnormalities. If the time taken for this is between 116-121 seconds, the tape motor speed is within tolerance.
Noise Diagnosis (Dead Space)
Use this portion of the tape for noise diagnosis, such as alternator whine, switch pops, etc., which are more easily detected during dead space (blank space between songs). Refer also to Audio Preliminary Diagnosis .
