SCS 115 Sub - JBL Audio Service Manual (repair manual). Page 4

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Function generator/signal generator/sweep generator

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Integrated Ampilfier

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Multimeter

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Speaker cables

UUT = Unit Under Test

1. Connect two pairs of speaker cables to high level input terminal on UUT.  Cables should be connected to an

integrated amplifier fed by the signal generator.  Observe polarity of speaker cables.

2. Turn on generator and adjust so that speaker level output is 2.5V, 50 Hz.

3. Plug in UUT; red LED should be ON.  Turn power switch to the ON or AUTO position and turn LEVEL control

full clockwise.

4. Green LED should light, immediate bass response should be heard and felt  from port tube opening.

1. Follow steps 1-4 above, using a sweep generator as a signal source.

2. Sweep generator from 20Hz to 300Hz.  Listen to the cabinet and drivers for any rattles, clicks, buzzes or any

other noises.  If any noises are heard, remove driver and test.

1. Remove one or both drivers from cabinet; remove + and - wire clips.

2. Check DC resistance of driver.

Bass 15 should be approximately 5.5 ohms.
Bass 16 should be approximately 5.8 ohms.

3. Connect a pair of speaker cables to driver terminals.  Cables should be connected to an integrated amplifier

fed by a signal generator.  Turn on generator and adjust so that speaker level is 5.0V.

4. Sweep generator from 20Hz to 1kHz.  Listen to driver for any rubbing, buzzing or other unusual noises.

Even though the Bass15 and 16 seem to have an on/off power switch, in fact the switch does not switch
the main power off to the amp assembly, even in the OFF position.  All AC and DC voltages within the
amplifier are still active, so for safety concerns the AC power cord should be unplugged before any
servicing begins.