# JL HD 750/1 going into Protection Mode



## gnesterenko (Mar 17, 2011)

Ugh - this may be my punishment for buying a used amp from eBay and not one of these forums... A disclaimer should be noted - I've not checked any voltages yet, but connections seem secure... though I will go over all of them as soon as it stops raining to double and triple check.

Long story short - I have a 750/1 powering a Shiva X2 for a little over a week. Was working and kicking in a really good way right up until yesterday. On the way home I noticed the sub cutting in and out. It was strange because it seemed to be timed to the bass-kicks and measures, so at first I thought I was hearing detail in the track that I just didn't realize was there before. No such luck, upon getting home, I see that the status LED is blinking amber/red indicating a voltage drop and/or internal amp fault (per the manual). Then it would switch back to green and the sub would resume play for a few seconds at a time, before the amp would again go back to flashing amber/red. This happened a few times until, in front of my own eyes, the amp went from kicking in and out of protection, to a constant state of protection mode. Now it will not come out of it at all, permanently in protection mode.

I should note that I never pushed this sub as hard as it was capable of going... because I hadn't specifically set the input sensitivity yet (was getting to that point), I was very conservative and had the dial set to about 1/4-1/3 of the amps max gain and at the 'low' input sensitity rating (HU is 2V max), so I couldn't have been pushing more then 300 or 400 watts through the sub, which should handle 500-1000... Crossover was 70-75hz at 12db slope. Subsonic filter defeated as using a sealed enclosure, per instructions.

The JL HD 600/4 sitting right next to it is ticking along like clockwork though... no issues to report - has been in the car far longer (over a month) and pushing my Imagines just fine. Never had an issue, and since both amps are running off the same power system (distribution and grounding blocks).

So I'm appealing to the DIYMA community for help in terms of steps I should take to troubleshoot and identify the actual source of my gremlin. First, things I've done so far:


 Listen to sub up close while the amp was still coming on and off for signs of damage. Seemed to sound clean, but I also decreased the input sensitivity a bit as a knee-jerk reaction thinking I was damaging my sub... I did note two things though - 
when listening to particularly sub-heavy beats, the sub made a noise... I would say a mechanical one? Like flapping as the cone vibrated. It didn't seem to distort the actual frequencies produced, but rather exist along side with them. And only audible with my head right next to the sub - not from the cabin. Is this natural for subs when pushed?

Right before the amp kicked out for the last time, I *thought* I heard a mechancial 'clunk' or 'knock' from inside the sub box - but it was VERY feint and I'm not sure if I heard it at all, could have been my imagination. And I only 'maybe' heard it the very last time before the amp went into perma-protect mode. Not the other times the amp kicked in and out.

Checked the temperture of the amp at the time this was happening. Barely warm to the touch, and cooler then the 600/4 next to it.



Turn off subwoofer output at my HU - no point trying to push power through it until I know what's wrong.

*Planned Troubleshooting course of action:*

Double and triple check all my power wiring connections at the battery, fuse, fused distribution block, amplifier plugs, ground block, and finally the chassis ground location.
Check the voltages between each step in the circuit to look for voltage drops (battery positive and fuse block, fuse block and ground block for the 750/1, fuse block and ground block for the 600/4, fuse block to ground block general, and finally power to ground general.
Unplug the speaker wires for the sub from the 750/1 and see if the fault remains - if so then its the amp and not the sub. Otherwise:
Bridge my 2 rear channels for the 600/4 and push the sub with those. Should identify if the subwoofer is the problem (don't think so as the indicator LED should be a different color per the manual, but I don't trust such simplistic diagnostic indiciator entirely)

Is there anything else I should do in terms of covering all the basic points of failure? I'll get into what can be done about the specific problem once I identify exactly what it is and where it lies.... 

Thanks all in advance. Needless to say this is a major kick below the belt as my build was otherwise coming together nicely and I was getting ready to finalize my sound deadening and reassemble the car for the final time. Now looks like I'm back to the drawing board with potential expenses coming up to make it all work again... I R a SAAAAD panda...


EDIT: There is one other potential point of failure that I just thought about - the JL HD uses the removable plugs with set screws for the power/ground/turn-on and speaker connecctions. My power/ground/turn-on plug was missing one of the set screws (M8-1.25) so I replaced with a simple hex-bolt until I ordered some replacement set screws from McMaster. Hex bolt is big and extends beyond the actual plug pretty far... doesn't touch anything, but still, not 'stock' or as designed. That and its tip is not round and tapered like the stock set screws, but rather flat, so doesn't press the power wire into the socket in the same way as stock does. Perhaps this is the point of ground failure? Certainly going to look at that first and foremost...



Posting from work, so need this disclaimer:
"The views expressed here are mine and do not reflect the official opinion of my employer or the organization through which the Internet was accessed."


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## wild2319 (Jul 14, 2015)

I am suffering the same issue. there was a recall on the amps and i had mine exchanged. still the same problem. The only thing i can think of is a power issue. I changed all the wiring to 0 gauge checked all my grounds and so on. The only thing I haven't done yet was replace my battery. the AMP could simply being going in to protect mode since its detecting major voltage drops due to a faulty battery. my battery is 4 years old and is stock for a KIA Forte Koup 2011.


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## Jepalan (Jun 27, 2013)

It sounds like you are suffering from one of these two conditions (quoted from the user's manual). Troubleshoot accordingly...
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Constant Amber (yellow): lights to indicate that the impedance of the speaker load connected to the amplifier is lower than its optimum load impedance range. When this light is on, a protection circuit engages and reduces the power output of the amplifier.

The amber indicator will also light when a short-circuit is detected in the speaker wiring
(this can be a short between the positive and negative speaker wires or between either
speaker wire and the vessel chassis).

Alternating Red and Green: lights to indicate that the amplifier is experiencing a fault that may require service of the amplifier, its wiring or the vessel’s charging system. Audio is muted when this fault occurs. The most likely cause of this fault is a low supply voltage condition. If battery voltage drops below 8.5 volts at any point, the amplifier (except for the “Status” LED) will shut itself off to protect itself and the vessel’s charging system. If the voltage drops below 6 volts, the “Status” LED will also turn off.

The amplifier will turn back on automatically when voltage climbs back above 9 volts. This shut-down and turn-on behavior may happen in a rapid cycle when bass-heavy program material causes a weak charging system to momentarily dip too low. If this is happening in your system, have your charging system inspected to make sure it is working properly.

If no problem is found with the supply voltage to the amplifier and you are still seeing alternating Red and Green on the “Status” LED, it is likely that the amplifier is suffering from an internal fault that requires factory service.


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