96 EB subwoofer not working

[thor1701]

so i have a 96 eb, and as far as i can tell there's nothing wrong, no broken wires no blown fuses, nothing, one day i noticed there is nothing coming out of that subwoofer at all, so other then checking the obvious, fuses wires and whatnot, is there a way to test that power is getting to the amp or other ways to find out if the thing is bad or not?

also i have no idea how to upload pics to this, i took a pic of the head unit and the subwoofer, also this is a jbl system

 

[toypaseo]

Factory sub amp failure is a common problem.

 

[thor1701]

Factory sub amp failure is a common problem.

so i've heard, but i'd like to make sure that's the problem before i replace it

 

[1996BLKBauer]

so i've heard, but i'd like to make sure that's the problem before i replace it

Take the amp out open it up and look for burnt up resistors, there is more to it then that, but that what physically show when they fail.

 

[J_C]

It's modular to the extent of having a factory wiring harness & 1 or more connectors for it yes?

You can use a multimeter, while music is playing, to probe for 12V and ground to confirm it's getting power. Similarly you can keep one probe on ground and probe the remaining connector contacts on low (single digit) AC voltage range on the meter to probe for input signal. If it is getting 12V power and input signal above a few millivolts then the problem seems to be in the amp itself.

Certainly as 1996BB suggested you should look for burn marks on the PCB or burnt resistors. Another common power amp failure is the last stage power transistors, which are generally larger and on a heatsink. They may fail with no visual clues but if it comes to it there are ways to test those with a multimeter too, briefly it's with a multimeter again, measuring if there is a base (pin) drive current, input voltage, and then if there's no output voltage (as audio to the driver) then the transistor is fried.

If the transistor is instead fried shorted or leaky, or an upstream transistor was shorted or leaky then it could have caused an over-current condition that blew a fuse or tripped a breaker.

If you feel the amp itself is the problem it might help if you posted a good, straight top-down and corresponding orientation, bottom up picture of the circuit board, in the highest resolution you can manage, hosted on an image hosting site then linked here.

 

[thor1701]

i will pop it open tomorrow and have a look, i already have a few pics of what i do have, but i do not know which image host to use

 

[J_C]

i will pop it open tomorrow and have a look, i already have a few pics of what i do have, but i do not know which image host to use

http://www.imgur.com is one example. Follow the directions they provide then copy and paste the "Linked BBB Code" in a reply here.

 

[thor1701]

ok i think i got it

 

[thor1701]

ok i think those were way toooooo big...

 

[J_C]

Too big for here but not too big to see on imgur. Did I tell you the wrong way to do it or did you copy and paste something besides the BBB code? You could just edit the post and link to the imgur page instead.

Regardless, I wasn't talking about pictures of the head unit, rather pictures of the sub amp which is in that silver case next to the speaker. You'll need to remove it, test the connector as described with a multimeter, then if power and signal are getting to the connector on the wiring harness then it's time to disassemble the sub amp and examine it and/or take pictures...

EDIT: ... but before going to the trouble of taking the amp apart, I'd use a multimeter to check resistance at the speaker terminals (on the speaker while unplugged from the sub amp). A blown speaker coil would also cause no sound and would be indicated by an open circuit reading rather than a single-digit ohm, resistance measurement.

 

[thor1701]

yes i knew what you wanted, i just put those there to show what i had, because the few post's i've read they post pics of the head unit to show if there's a button or not for the subwoofer, i will be taking more pics tomorrow, and it looks like i fixed the issue with the pics

 

[J_C]

... but before going to the trouble of taking the amp apart, I'd use a multimeter to check resistance at the speaker terminals...

 

[4rd Xplora]

Or hook up another speaker and see if it plays. When mine stopped working, I cut the wires from the amp to the sub (on the backside of the sub) with enough of a lead to solder them back together and hooked them to another speaker. It played then I replaced it with another high dollar 6 inch (I think) sub woofer.

 

[thor1701]

yes, blown speaker, how or why i have no idea, i never blast my sound on my truck, just kind of weird, now to replace it, any idea what size it is and wattage or whatever? i've never actually bought a speaker before lol

 

[J_C]

Keep in mind that a failed amp can blow a speaker. Get the speaker out of the enclosure, measure it, get a model # if there is one stamped on the back. I know nothing about the sub speakers Ford used but given the internet era it shouldn't be too hard to find something equivalent online for a lot less than an OEM Ford sub assembly, plus if a replacement is as old as the original then the surround may be dry rotting already.

As for testing the amp, with music playing you can use a multimeter to check for DC offset. There should be a very low #, dozens of mV DC voltage at most on the amp speaker output terminals, yet more than that of AC voltage present as the audio signal.

There is more info about the subs in this forum. For example here's one of the topics:
http://www.explorerforum.com/forums/showthread.php?t=184899

 

[thor1701]

ok so if i am reading this correct, switch my meter to dc and measure at the sub output? i did hook up another speaker to it just to make 100% sure i had a bad speaker and sound came out of that one

 

[J_C]

Yes, the DC mV scale, often either marked as 200mV or 400mV, or if those aren't present then 2V scale or 4V. It depends on your meter's capabilities which range to select if it's not an autoranging type meter, although that was a test to verify the sub was working okay before risking another speaker. If there was a shorted or leaky transistor or IC then it could climb to even more than 4V DC. Any DC creates heat. Too much heat will fry the voice coil.

Ideally an amp is supposed to have no DC, to output as close to 0mV DC as possible to the speaker but a few dozen mV is an acceptably low #. If you got sound but it didn't burn out the new speaker's voice coil then the amp is probably fine.

 

[thor1701]

ok i will check it tomorrow with the dc mv and post what it says
i've read up on other post's and i believe that what i have is a 6.5 inch 8 ohm speaker, but im not sure on the wattage, does it matter? i see some that are 200, with 100 rms and some say 600?

 

[J_C]

Higher wattage is better but there are other factors as well that may be more important once you narrow down your choices. 100W does seem on the low side but I am thinking in terms of aftermarket subs, not OEM which can vary wildly in quality and power handling.

I just saw a page on Crutchfield.com that states the newer Explorers had only a 60W + 60W amp but that into an 8", 1.2Ohm dual voice coil sub.
http://www.crutchfield.com/S-JEXeyuMjjsq/learn/2002-04-ford-explorer.html

It does look like the '96 JBL system had a 6.5" sub and all I could find was the amp is 85W. The bigger issue may be the depth of the enclosure, and what modifications it needs.

Edit: Note that I often edit posts a few minutes after making them.

 

[thor1701]

this looks to be the best way to go, im not looking for anything fancy, just something to replace back there
http://www.ebay.com/itm/Pyramid-Pro-WH68-1-Way-6-5-Car-Subwoofer-200-Watt-High-Power-8-Ohm-/141485364146?pt=Car_Subwoofers_Enclosures&hash=item20f12f53b2