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Thread: JBL/UREI 6230 transformer hum problem

  1. #16
    Senior Member Russellc's Avatar
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    I enjoy my 6230 a lot also. I also got it off ebay, about the same price shipped, ( under 150) and like yours, had some problems. It hummed like yours, and one channel would drop out, and come back it you jiggled it.

    If you take the top off, you'll usually see where someone has added a wire, I inquired about it on mine here and was told it was anextra ground wire many added to reduce hum.

    I had to basically reflow most solder joints.....These things have run fro hours on end and the transformer vibration slowly breaks them down over the years.
    All the output devices, and so forth. If you search on this forum you will also found that there are three small value caps on the board associated with regulators I believe, and they stand right next to these toasty devices and get backed to death.

    After all this, you want to see what kind of DC is coming out of the outputs. The power supply caps are remarkably durable, mine were still fine. Has worked fine ever since. This is basically a tank of an amp, its output devices are only being used at a fraction of their capacity. Once together, it should run fine another 25 years or so.

    Russellc

  2. #17
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    JBL 6230 Transformer Hum Problem

    I don't know if you solved the problem or not. I can suggest the following to aid in troubleshooting.

    Disconnect the bridge rectifier from the secondary of the transformer (push on tabs). Turn on amp. If hum still there it is the primary windings that are loose and vibrating (not much to do about this). If hum gone, turn off amp and reconnect rectifier. Disconnect the positive and negative leads on the PS large caps that go to the boards. Turn on amp. If hum gone possible bad caps or big load on PS. Turn off amp. Reconnect PS Caps and disconnect + and - leads to boards. Turn on amp. Hum gone- problem is on boards causing big pull on PS loading transformer causing hum (normal). Hum still there bad caps (and or rectifier).

    Hope this helps

  3. #18
    Senior Member Russellc's Avatar
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    Quote Originally Posted by KVThere View Post
    I don't know if you solved the problem or not. I can suggest the following to aid in troubleshooting.

    Disconnect the bridge rectifier from the secondary of the transformer (push on tabs). Turn on amp. If hum still there it is the primary windings that are loose and vibrating (not much to do about this). If hum gone, turn off amp and reconnect rectifier. Disconnect the positive and negative leads on the PS large caps that go to the boards. Turn on amp. If hum gone possible bad caps or big load on PS. Turn off amp. Reconnect PS Caps and disconnect + and - leads to boards. Turn on amp. Hum gone- problem is on boards causing big pull on PS loading transformer causing hum (normal). Hum still there bad caps (and or rectifier).

    Hope this helps
    This is the best advice, I doubt your problem is with the transformer, more likely something down steam has run a muck and is causing the transformer to load down. Chase it down like the above poster suggsts.

    Russellc

  4. #19
    Senior Member caladois's Avatar
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    Can the home AC quality generate transfo hum ?
    Regards Stephane

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