millsmobile
Like my world didn't already have enough hum. My subwoofer is really starting to annoy me. It had a minor problem right out of the box when I bought it in December. It hummed from time to time, but giving it a light smack on the top would stop it. It wouldn't happen again for some time. The sub is a JBL S120P II. I bought it from eBay and it came sealed in a factory JBL box with all paperwork also sealed. However I highly suspect that it has been remanufactured. One of the screw down caps for the speaker connections is a slightly different red than the other three.
The sub has been humming more often, and taking harder and harder smacks to make it stop. It is clearly a 60hz hum. It doesn't matter if the volume is max or off, and no other setting changes the volume. Removing the LFE cable reduces the hum slightly, but I don't think the problem is here. Has anybody had experiences like this with a powered sub? If I find out today that JBL won't cover it, I am going to take it apart. What should I go after first in there?
The sub has been humming more often, and taking harder and harder smacks to make it stop. It is clearly a 60hz hum. It doesn't matter if the volume is max or off, and no other setting changes the volume. Removing the LFE cable reduces the hum slightly, but I don't think the problem is here. Has anybody had experiences like this with a powered sub? If I find out today that JBL won't cover it, I am going to take it apart. What should I go after first in there?
发表时间 Fri 01 Jun 07 @ 4:21 pm
sleeperawaken
You've got a ground loop problem, something intermittent. If you are not beyond your warranty period, it should be covered. You should have taken it in first thing, but I think you know that, so I won't harp beyond that comment.
If you are not an electronics repair person, do not try opening it up yourself. I work as a repair technician as my day job, and I have never seen a good repair done by a customer, and often times, they wind up pay a load more for repair, because the damage they did while "trying to fix it themselves" was worse than the original problem.
If it is out of warranty, talk to your friends, try and find someone you know or your friends know that know a decent amount about electronics (not just fiddling, but actually time in college on the topic) that also has some excellent soldering skills. Describe the problem to him/her, and if theyhave atleast enough knowledge to say, "that sounds like a ground loop problem", then that person may be able to fix your problem.
Or, if you are not shy of spending some good money, you can try to get a good referral to an electronics repair place. Don't just pick one out of the yellow pages, get a referral.
2 cents.
发表时间 Fri 01 Jun 07 @ 6:44 pm
millsmobile
I do have some college work in electronics, and am handy with solder. I bought it cheap, $300 to my door if I remember. The thing that sucks is I have to pay to ship it to JBL. It weighs about 60 pounds, and comes in a box that I would have made a fort out of when I was younger. It is under warranty now, but you know how that goes. If it isn't covered under warranty, I need to pay to ship it both ways plus the repair.
Obviously if it can be temporarily fixed by hitting it, something is loose. Guesses?
Obviously if it can be temporarily fixed by hitting it, something is loose. Guesses?
发表时间 Fri 01 Jun 07 @ 7:45 pm
A Man and His Music
It will not hurt to open it, and see if you can find the loose connection. If it is obvious, you may be able to repair it yourself. On the other hand, you may void the warranty if you open it, so look for any stickers. If you can't find the problem, bite the bullet, and send it back.
发表时间 Fri 01 Jun 07 @ 8:09 pm
GaryBr
Consumer law in the UK says that the individual shouldn't have to pay courier costs for returning a product under warranty.
If JBL don't want to pay the charge, then they have to collect it or repair it in your home.
Don't back down to these people.
If JBL don't want to pay the charge, then they have to collect it or repair it in your home.
Don't back down to these people.
发表时间 Fri 01 Jun 07 @ 8:28 pm
millsmobile
I think I will open the thing up. It will probably cost me two bills to get it fixed, JBL's warranty leaves lots of spots for exclusion.
Id love to see them come fix it in my house! LOL too bad I am in the USA.
Id love to see them come fix it in my house! LOL too bad I am in the USA.
发表时间 Fri 01 Jun 07 @ 8:34 pm
halo_djk
Sounds like a dry joint on the circuit board. I'd unplug it, and go through with a soldering iron and resolder anything that looks suspect.
If that doesn't work, go back and solder anything that "Doesn't" Look suspect!
If that doesn't work, go back and solder anything that "Doesn't" Look suspect!
发表时间 Sun 03 Jun 07 @ 6:51 am
millsmobile
Update. I haven't touched the thing yet but I am 99% sure of the problem. I did some touch up reading on some of the components there, and it sounds like the electrolytic filter capacitors. These are the suckers that filter the 50-60Hz from the power supply so it doesn't run through the audio circuitry. I learned that they are designed to have a working life of 10+ years, but they only have a shelf life of 5 years before breaking down. If the sub really is new, it sat in that box for about 6 years. The capacitors are also susceptible to physical shock. They cost about 1$.
发表时间 Sun 03 Jun 07 @ 2:24 pm
millsmobile
I removed the plate amp yesterday and didn't find anything else suspect. I am fairly impressed with the overall build quality, it weighs a ton, all the wires are twice as thick as they need to be, and the solder joints are very good.
Unfortunately there is also a liberal application of hot glue, I'm assuming to reduce vibrations. The two big ones are the filter capacitors, glued together down the middle. To really do it right all of them should be replaced, but look at those gobs of glue! Bastards.
My excitement in doing it myself has dimmed somewhat. Time to chase JBL. Of course I button it back together and there is no hum so far. Go figure.
Unfortunately there is also a liberal application of hot glue, I'm assuming to reduce vibrations. The two big ones are the filter capacitors, glued together down the middle. To really do it right all of them should be replaced, but look at those gobs of glue! Bastards.
My excitement in doing it myself has dimmed somewhat. Time to chase JBL. Of course I button it back together and there is no hum so far. Go figure.
发表时间 Mon 04 Jun 07 @ 7:06 pm
Tear Em 'Up
it might have been a ground issue and by removeing and replacing the unit you gave it a more secure ground connection. Almost everyone uses ground switching for electronics anymore..
发表时间 Mon 04 Jun 07 @ 10:11 pm
millsmobile
I wish it was that easy. The amp doesn't use an external electrical ground. There were a ton of screws holding it in but they all went into the wood. I played this morning before work (empty house) and managed to coax earthquake style hum out of the thing.
发表时间 Tue 05 Jun 07 @ 9:09 pm