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Seeking Help: JBL LSR 308 Schematic Diagram or Service Manual


Where can I find the schematic diagram or service manual for the JBL LSR 308?
I can't seem to find it.

The speaker suddenly started crackling out of nowhere, even without any connected input.
Please see the video at the bottom for a sample of the sound.

I took it to an electronics repair technician yesterday, and he mentioned that the power amplifier is functioning properly, but the preamplifier section is not working well.

However, he's unable to find the schematic diagram or the service manual for the JBL LSR 308.

He mentioned that he needs these resources to diagnose the issue.

Any assistance in finding the schematic diagram or service manual would be greatly appreciated.

Video of the speaker issue:

Thanks for your anwser,


  • Hello,
    Strangely I have the same issue you describe here https://www.youtube.com/watch?v=fehPdNZr0a0 but on a LSR305 Series 3. However mine its a bit intermitted, and the static is heard as a background noise, and it appears to your ear as distortion. The noise is coming out from both, the Bass speaker and the tweeter.

    I have looked into it and it appears to me that the issue is with the STA350BW Digital Audio amplifier (available from Mouser) or the A/D converter Cirrus 5341CZZ (Not available)

    I have checked voltages around the PCB board and they seem to be alright according to what is specified on the board. So my logic is what drives the speakers ? What drives them is this chip STA350BW which is common to both speakers (Tweeter and Bass), unless the noise is coming from the A/D converter which is something I cannot trace.

    However the noise seems to be disappeared when the device is on for a minute. Shutting off and then back on again needs a minute to disappear.

    Strangely no-one answered from the forum just yet. If they cant give us the manual, they could be dropping us a line as to what could it be !!

  • JSunJSun Posts: 2

    You can try to probe pin 10 on IC27 (CS5341) to check if any noise exsits. If yes, then it's a front end issue, check circuit of IC11 on the input board. If no, try to replace IC27 or IC28, there isn't much components in the audio signal path.

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