JL Audio FATHOM “Power On” cap amplifier repair - step by step guide for repair at home.

Step by step repair video with more useful info & links below: My JL Audio Fathom Sub was not powering on… It was dead with no lights coming on, but I had an idea of why.

After thinking and researching it a bit, I concluded the issue is the “power on” portion of the amplifier board circuitry. As I researched further, I found that this is indeed what the issue is and others have experienced this as well. When it comes to most home theater subwoofers, many people complain that the caps go out on subwoofer amplifiers, and yes this is common for the caps to dry out with age, but this particular problem has NOTHING to do with the large power amplifier caps… This is a problem with the simple power on capacitor on the amp. If your JL Audio Fathom is dead and not coming on, this is likely the problem.

This is a step by step video guide of the repair on my JL Audio FATHOM F113 subwoofer. This also pertains to the other Fathom models, like F110, F112. I also assume the F212 and JL Audio GOTHAM sub models might run into this as well.
This repair is basically for the Version 1 subs. Since they are older, they will likely see this issue before any Version 2 models.

I do know the V2 model subwoofers are built with “better caps” installed from JL Audio. I’m not sure if the capacitors in the V2’s are strictly better large “power amplifier” caps or if they also used better caps throughout the entire board including the “power on” cap…? I suspect the size of the cap would help identify the change, if the V2’s have a larger sized cap like the one I used vs the tiny original cap I removed. Another thing I noticed about the V2 models is since they proceed more power, I believe JL upgraded the magnet on the subwoofer and it is slightly larger than the V1 models.

Most of the information gathered to complete the repair for this video was from the AudioAficionado.org forum. I am not a member of the forum but was able to obtain enough information from the group to make the repair. I’m SUPER EXTREMELY Thankful for “jdandy” for making the post in the first place which I stumbled across in a google search to fix the sub.

About the actual woofers themselves… from what I can tell… after spending many many hours being intimate with these woofers (working on about 6 of them). The Version 1 Fathom woofers and the W7 model car woofers are the exact same woofers (except for the version 2 Fathom models that have a slightly larger magnet like mentioned above). I did come across something indicating the foam surround was a little thinner on the Fathoms compared to the car W7 models, but I did not find that to be true and no other researched backed that up. So if you need a new woofer for some reason, you can buy a used car model W7 and carefully swap out the little “JL” button on the front dust cap and you will be fine.

TIPS FOR YOUR FATHOM SUB:

1. To give your Fathom a long life, it might be best to simply leave the sub plugged in permanently to the wall and keep the front power switch in “auto” mode.

2. If your Fathom is not currently turning on, you might still get some life out of it before having to replace the capacitor. From my experience, you can unplug the sub fully for about 48 hours. This will typically let the caps drain giving them another chance to charge up when the power chord is plugged in. After 2 days, plug in the power chord and see if the amp powers on. (Don’t forget to listen for the “click” after about 3 or 4 seconds of initial plug in of the man power chord.) If it does not power on, go ahead and turn the switch to “on” or “auto” and leave it there.
3. Your foam surround will eventually rot, especially in the Version 1 Fathoms. Purchase the new foam surrounds from SIMPLY SPEAKERS. (can also find them on Ebay). https://www.simplyspeakers.com/search...

ADDITIONAL FATHOM VIDEOS I MADE:

1.    • JL Audio FATHOM / GOTHAM / W7 Repair - rat...  

2.    • JL Audio FATHOM - WHAT'S INSIDE your FATHO...  

HERE IS A REPLACEMENT CAP FROM DIGI KEY:
https://www.digikey.com/en/products/d...

I hope this video and information helps someone else out there. I am passionate about JL Audio Fathom & W7 subwoofers. I took the time to rip into these super expensive Fathoms to make it easier for you. I also have JL Audio W7 subs in our cars. A 13W7-D1.5 and a 10W7AE (AE - Anniversary Edition). They are amazing subwoofers and with a little knowledge on how to repair them, they will last you many many years! Best of luck to you! :)