Question about Jl Audio 500/1 Car Audio Amplifier

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Sleuthing a 300/4 low-ohm issue. 300/4 amp history: unknown. just connected today whole system yesterday/today: head unit, 300/4(to 4 polk 6.5" component speakers brand new) 1000/1 (4-W3's), to brand new polk door speakers (4 ohm), 1600 watt scosche wiring to dist-block, 1 farad cap on 1000/1. amp plays, no distortion, all is good...until...I begin to turn the volume up, at that point the low-ohm flashes on/off intermittently, at higher volume it blinks more often then stays on....while music plays, until very-loud now, amp cuts out. green light stays on. after short pause and lower volume, amp cuts in again. source voltage hot = 13.9v, used a grinder to clear grounding connection. meticulous detail. I have repaired amps before by replacing output mosfets (digi-key). knowing that heat affects all circuits, would it be likely that i have an output mosfet that is on its way out and due to heat, and as the amplification output increases it begins to short? I did run multi-meter to each mosfet and did not see any near-shorts. (of course thats when its all cooled down though) thanks for your input.

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Are you sure you getting enough power to push everything. I have seen when the voltage is too low coming in, the amps will shut down so they don't overheat. Once they've cooled off and the volume level is lowered they will kick in again. Low voltage and a heavy draw will create massive amounts of heat.

Posted on May 25, 2011

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  • matthew walsh May 25, 2011

    remember, its the 300/4 that's cutting out with the low-ohm indicator, not the 1000/1. It uses the same distribution block as the 1000/1 so if an amp was to power down due to low-voltage: a: the low-voltage light would activate on the 1000/1, and b: it would be far more likely that the 1000/1 drops first IMO.

    I'm thinking the unit itself has a quirky (read dying) internal component. The question is: what component would most likely be the culprit to produce this scenario.

  • ray0427c May 25, 2011

    Sorry MAW31 I've never driven that far into an amp. I would normally either return the amp if possible or get a new one. Have you tried running the 300/4 by itself unhooking the 1000/1 to see if you get the same response. Just a suggestion. It could be the 300/4 has a more sensitive heat response. If not sorry I couldn't help

  • matthew walsh May 25, 2011

    thanks for your input ray.

    Its not really a heat issue as this is reproducible right from the git-go. turn it on, get to 1/4 volume and the low-ohm indicator begins to flash...and more quickly as you get to 1/2 volume. if you turn volume back down, indicator stops blinking.

  • ray0427c May 25, 2011

    Good luck MAW31. Let me know what happens and I'll try to spread the word.



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