Tools Required

J 39916-A  Delco Audio System Diagnostic Kit

Use the J 39916-A in order to test and evaluate the following audio system components:

The J 39916-A uses the following test tones:

The J 39916-A also contains instructions for cleaning the tape.

Use the 50 Hz tone in order to evaluate the bass response of an audio system. You may also use the tone in order to evaluate audio systems that have separate subwoofer amplifiers and speakers.

Use the 500 Hz warble tone in order to evaluate the response of the midrange speakers. The 500 Hz tone qualifies as a warble tone because the audio characteristics of the 500 Hz tone are different than a sine tone. The 500 Hz tone produces a warble sound. Use a warble tone in order to evaluate midrange frequencies because the warble tone makes the tone source easy to identify. A sine wave may set up a standing wave in the vehicle. The source of a standing wave is difficult to identify.

Use the 8.5-9.5k Hz spectral tone in order to evaluate high frequencies. The spectral tone is a section of frequencies of equal amplitudes ranging from 8.5k Hz to 9.5k Hz. The spectral tone sounds like a group of crickets chirping. Use the spectral tone for the following reasons:

You may use the combination tone if you are familiar with the dialogue on the beginning of the tape. The combination tone is a blend of all 3 test frequencies. When you use the combination tone, you may hear 3 distinct sounds. Listen to these sounds. By comparing the sounds in the left front speakers, you are able to determine if there is a speaker problem.

Always compare the front speakers to the front speakers. Always compare the rear speakers to the rear speakers. Do not compare the front speakers to the rear speakers. The rear speakers could be different from the front speakers. If the rear speakers are the same as the front speakers, the rear speakers could have a different mounting environment. A different mounting environment may cause the rear speakers to sound different from the front speakers.

Use the combination tone for the following speaker problems:

While using the combination tone, make comparative voltage measurements on the speaker terminal. Ensure that the following controls are in the detent position:

Use the voltage measurements in order to diagnose one of the following components:

Use the 50 Hz to 8k Hz swept sine tone in order to diagnose rattle in one of the following components:

Use the 2 test tones in the swept sine tone portion of the tape in order to diagnose rattles. Use the first of the 2 tones in order to play 2 variable frequency tones back to back. The second tone is also a variable frequency tone. The change in the frequency of the second tone is slower. Use the second tone in order to repair one of the following speaker problems:

If the customer has already isolated the problem, place the fade and balance controls in the specific problem area.

If the customer complains of one of the following sounds coming from the speaker during certain sections of music, use the swept sine tone in order to verify and repair problems associated with the complaint:

There is a 2 minute time period marked in the tape in order to inspect the cassette tape motor speed. The tape tells you when to start timing the event. Then the tape plays about 1 minute and 50 seconds of music. Finally, the tape tells you when to stop timing the event. If you time the event between 1 minute and 50 seconds and 2 minutes and 1 second, then the tape motor speed is within specifications.

Use the 2 minute time period on the tape in order to verify or resolve problems when a customer complains that the audio from the cassette sounds abnormal. In some cases, improper speed of the tape motor causes abnormalities in the audio.