Altec Lansing ADA885 Sub cutting out

Discussion in 'Sound Cards and Speakers' started by dsmdavid, May 28, 2009.

  1. dsmdavid

    dsmdavid New Member

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    2
    I recently came into ownership of a set of Altec Lansing ADA 885 speakers w/Subwoofer.

    I have extensive knowledge in the car audio field, yet I am perplexed as to this issue...

    Upon setting up the speakers, they worked fine, great sound, true bass, everything was going fine. Then the sub woofer stopped working. I turned off the speakers, left them alone for a couple hours (thinking maybe I was jamming to loud and sent the sub into a protection mode). When I turned them back on at a very, very low volume, the sub still cut's out (after about 20 or 30 seconds), and doesn't come back on until I turn them off for an hour or two and come back to another 20 or 30 seconds of clean bass only to be disappointed when it cuts out again.

    I am using the speakers with an analog cable right now, and my question is if I swap to a Digital S/PDIF cable would this possibly remedy the sub cutting in and out (due to faulty wiring inside the sub itself w/regards to the analog interface), or are the two completely unrelated at all and I just have a defective sub woofer?

    Thanks in advance!
     
  2. ZST

    ZST New Member

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    2
    My answer is: No.

    It's possible you have a defective subwoofer...
    Have you checked the amplifier, its temperature, when sub's working? It's possible the subs is cutting of because the temperature is too big and it happens so to prevent the sub's ampliefier damage
     
  3. PunterCam

    PunterCam New Member

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    1,039
    It's possible it could just be a dodgy connection inside the sub, open it up - can't do any harm. It heats up, something expands and loosens the connection to the sub. Worth a look.
     
  4. dsmdavid

    dsmdavid New Member

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    2
    ZST: initially, this was my thought. most sub woofers now have a built in protection to keep the amp from frying. usually due to really high temp. the speakers, cold, still cut's in and out. i'm sure it's a loose connection now. i can wiggle the sub around and the bass comes back, pure and clean.

    Punter: I tried taking the casing off, but the wires are soldered into the cabinet housing of the sub itself making it virtually impossible to unscrew anything else. however, I first looked at it really frustrated and probably missed something else I need to remove in order to remove the sub from it's cabinet. I will take a closer look tonight. Thanks for the help, but I think I've got it cornered to a faulty connection on the sub itself. When the bass kicks it causes the short, thus no more sound.
     
  5. SaimondvadDer

    SaimondvadDer New Member

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  6. jceb

    jceb New Member

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    1
    jceb

    I had same problem. Thought it was a heat tbl. I had to remove the speaker to get at circuit board underneath. On that board is a black relay and diode combo, about 2inches square which can be affected by heat. Labeled Massouse-ME 140FF 012-2h 12v DC. I noticed that just by touching this it would cause the sub to switch on and off. It turned out 1 of the 6 leads had a cold solder joint on back of board. A slight dab of solder fixed this aggrivating problem. NOte. It was easier using a walkman or such as a input to the green and tuning to an off station. That way you can work on table or bench.
     
  7. linkin

    linkin VIP Member

    Messages:
    13,511
    Good that you found the issue but please note the timestamp on posts, you just posted in a thread that was over a year old :)

    Welcome to the forum
     
  8. tony212

    tony212 New Member

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    Thank you.... it worked.

    Been bothering me for years and have been checking online with no real solution. Funny that I just bought Logitech speakers this morning and decided to search online again. Planning on cancelling the order.
     
  9. ragejg

    ragejg New Member

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    3
    I just started a thread about this here:

    http://www.nvnews.net/vbulletin/showthread.php?t=157605



    ... but it seems that this issue was covered well here. I didn't know there was another PCB in the subwoofer box, I'll look harder next time. Any idea what the big cylindrical part is? Maybe I don't have to replace it now, but I'd still like to know what the heck it is.
     
  10. ragejg

    ragejg New Member

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    3
  11. kena999

    kena999 New Member

    Messages:
    2
    ada885 subwoofer amp repair notes

    I had one of these ada885 units that i bought from a hamfest a few yrs back....had no clue what it was all about, but it certainly is an interesting piece of stuff, so i bought it for the 10 or 15 bucks the guy was asking...

    several years (yes, years...its a disease) later, i hooked up the speakers and played around with the system only to find that the sub was out.. I looked around on the inet for a schematic but found nothing except some guys complaining that altec wouldn't give them a schematic....lol

    i burrowed into the sub box and found the hidden sub amp which is in its own metal case under the sub driver baffle board....the unit had roasted the circuit board in the area of the coils on each channel of the 2 channel amp....i think the heat from the coils also roasted some surrounding parts which were melted or destroyed....this two channel amp drives the two voice coils of the dual voice coil sub driver.

    Well, the amp turns out to be a single chip pwm (pulse width modulated) class d type unit...schematic of one channel is attached to this post....this is not the schematic of the altec amp, but the general topology of the section that burns up is identical.

    the parts on the output are to block the pwm oscillator signal from getting to the speaker....all these parts had burned up on the board....some of the tracks on the board were also in bad shape and i jumped a few with wire as necessary to restore their integrity....

    I replaced all the output parts (3 caps...560p, .1uf, and .47uf, 1 resistor...150ohm, and the 60uh coil) as shown on the schematic with the values listed on the schematic....im not sure if these were the original values, but they do work....its easy to trace which parts these are on the board....just start at the coil burn spot and youll pick up the three caps...two on one side and one on the other....my board had provision to parallel more caps but were not used....

    Now heres the funny part....the iron core inductor that forms the LC trap heats up by design....and it runs way too hot for where its at...my first thought was to just move it off the board, but my background in crossovers and filters made me think that there was a better way to do this...

    Turns out that replacement of that iron core inductor with an air core inductor of the same (or close) value, solves the heat problem completely....I had some coils wound on 1 inch diameter wood dowel...about an inch long....and about 3 layers thick of #18 enameled magnet wire....they were labeled 100uh...pretty close to the 60uh called for....(I made these coils over 30 years ago when I was building the worlds most fabulous 3 way speaker...with the then new philips soft dome tweeter!) I ran extension wires from the coil areas on the circuit board, and wired them to the coils outside the metal box and bolted them to the inside wall of the sub cabinet because the heat on this coil type was non existant....back to listening!

    You can wind a suitable coil on a 1 inch diameter dowel rod, about 1 inch long....3 layers of enameled #18....i doubt that changing the spec on this coil is going to make much difference in the outcome....so i see no need to actually measure the value of the coil...its a very high frequency trap and the main point here is to use a large air core inductor instead of a iron core. I also replaced the three capacitors with mylar types, and the original had one polystyrene in there....not sure what the other ones were as they were totally destroyed...they worked just fine.

    So more than likely, if your ada885 subwoofer is out, and there arent any loose connections to the driver like some of the posts described, you probably have a burned up amp, and now you have the data to repair it....

    The pics posted from the other guy in this thread of the sub box should be good enough to lead you to the sub amp in the metal chassis....

    I have been in audio service for over 40 yrs.....so I have no problem poking around inside these sorts of things, but if you have little experience, just make sure you only do your repair with this thing unplugged for safety....
     

    Attached Files:

  12. kena999

    kena999 New Member

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    unanswered question...."cylindrical thing"

    there is an unanswered question in this thread about a "cylindrical thing" in the sub box....thats the power transformer. Its a toroidal type, hence cylindrical...
    Its a really heavy duty one, so Id be surprised if it ever went bad.

    The click you are hearing is from the relay in the amp which switches the output lines of the power amp to the subwoofer. I didnt have trouble with mine, but another post here described a defective solder joint concerning this relay...
     
  13. Proteous

    Proteous New Member

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    1
    ADA885 Subwoofer

    Hello Kena999,

    I loved my ADA885 speaker set it has awesome sound, however like yours the subwoofer on my unit just died. I would be willing to pay to have the sub repaired if it is possible. Would you be willing to have a look at my unit and see what you think? I would compensate you for your time and expertise and also ship it to you and back etc.

     

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