Thursday, September 05, 2019

JBL SUB350 Dolby Pro-Logic Surround Amplifier/Subwoofer STK4151 – How to disassemble the sub-woofer, schematic diagram, general troubleshooting


Please do not try to attempt any repair work; if you’re not well experienced in service field.
The troubleshooting described here is the only thing you can do as a user.
Total System Output - 200 watts
Front channels – 35 watts x 3 @ .1% THD
Surround channels – 15 watts x 2 @.1% THD
Subwoofer – 65 watts @ .1% THD
Frequency response - 35Hz – 20kHz
Dimensions - 15 1/8 x 13 x 14 ½” (384 x 330 x 368mm)
Input Impedance - 20k Ohms
Audios output IC – STK4151
Weight - 34.5 lbs. (15.7 kg)
Troubleshooting
If there is no sound from any of the speakers, check the following:
• Make sure the subwoofer is plugged into an active AC wall outlet.
• Make sure the Master Power Switch, located on the rear of the subwoofer, is in the “On/Standby” position.
• Make sure there is a source – for example, a VCR or television – hooked up to the TV or tape/aux input jacks on The Source.
• Make sure that the program material is playing.
• Re-check the hookup connections.  
If most of the sound comes from the center-channel speaker, with little or no information from the surround channels, note the following:
Although most of today’s televisions are equipped with stereo audio output jacks, some stereo televisions have poor audio sections and are unable to provide a Dolby Pro Logic encoded signal. In the unlikely event that you experience this problem, connecting the audio outputs from your Hi-fi VCR, laser disc player, DVD player, or Satellite receiver directly to one of the inputs on The Source will provide a proper audio signal and allow you to enjoy true Dolby Pro Logic surround sound.
If there is no sound from the surround speakers or sound is very low, check the following:
• Check all connections between the amplifier and each of the speakers.
• Raise the surround volume  with the remote control.
• Make sure the TV show or movie you are watching is recorded in Dolby Surround.
If there is no sound from the center speaker, check the following:
• Make sure that the processor is in the Pro Logic mode. If it is in Phantom or Stereo mode, the center speaker will not play.
• Check the connections between the subwoofer and the center speaker.
If you have low bass output, check the following:
• Experiment with placement of the subwoofer. Remember, place the subwoofer in a corner to get maximum bass output from the system.
• Increase the level of bass, using the remote control.
• Adjust the level control on the rear of the subwoofer.
If you are having trouble picking up radio stations, check the following:
• Make sure the antenna is hooked up properly.
• Depending on your distance from the station’s transmitter, you may need to install an FM antenna on the roof or in the attic.
Sub exploded view
                              Exploded view
                             Schematic