Has my amp gone out?

Discussion in 'Audio, Video & Gadget Tech' started by MWright936, Jan 18, 2013.

  1. MWright936

    MWright936 New Member

    I have a single amp with one 8" sub in my silverado (I'm not that inclined with audio stuff, so I don't know how much power the amp has or anything). The amp was a hand-me-down from my brother, so it's been around quite a while (I would say 10+ years).

    About a week ago, I was on a 5-hour road trip, and all of the sudden my sub quit. I reached back and felt the amp, and it was pretty hot. I had driven that far in the past without issue though. Now, the sub doesn't come on at all. I checked all connections, and they are fine. Yesterday, I turned the stereo up really quickly, and it seemed to jump start it. The sub came on, but only for about 15 seconds.

    Does this sound like syptoms of an amp that has bit the dust? Any help is appreciated!
  2. Enkeiavalanche

    Enkeiavalanche Moderator

    I think something is putting the amp into protect mode First check the Fuses, But if it did turn on for a few then off again I would have a look at the Sub. If you can carefully push on it. Does it move smoothly? Or can you feel it hitting on the inside? If you have a meter test the Ohm's. What brand and model Amp and sub are they?
  3. zigger215

    zigger215 New Member

    I agree, I second the woofer as the prime suspect. Chances are, your connections are good to go, the one connection I would verify is your ground connection. It needs to be short and grounded right to the body, no seat bolt, no existing bolt of any kind. Shave the paint next to your amp ground and ground it solid. Grounds become loose over time...well, some grounds, I through bolt mine to the body with stainless steel hardware, that's the best way to do it.
  4. MWright936

    MWright936 New Member

    Thanks for the input!

    Sub looks good and doesn't bottom out if I push on it. It's an 8" RF Punch P2 (not sure if it's 2 or 4 ohm). The amp is a Sony XM-752X.

    I checked the ground, and it's still solid. I already have it connected directly to the body near the amp.

    I have everything mounted firmly, so nothing moves around (other than movement with the vehicle, obviously). I never abuse it and just crank up the volume. It's just to improve sound, not to vibrate the neighborhood. What's weird is that it happened randomly in the middle of a song, so I couldn't really see why it would go out like that. It's also weird that it came back briefly the other day.

    Any other suggestions I could follow up on?
  5. Enkeiavalanche

    Enkeiavalanche Moderator

    Know anyone with a MutiMeter? Have the Sub checked...
  6. MWright936

    MWright936 New Member

    Ok, try not to laugh too hard because this is going to be a dumb question....I have a multimeter but don't know how to use it. How would I go about checking the sub with a multimeter? If it's too complicated to explain, just say so, and I'm sure I can figure it out via internet searches.
  7. Enkeiavalanche

    Enkeiavalanche Moderator

    There is a setting for Ohm's find that on the dial and put the needles in where the wire goes where you hook up the amp to the box.. Tell us what it reads..
  8. MWright936

    MWright936 New Member

    Ok this is weird. I don't get a reading on the multimeter. But...I've tried to test things with it before and never got a reading, so it might be bad (I set it up according to the directions for the meter). The weird thing is when I had the stereo on, and I pushed lightly on the sub itself, it would work. It might keep working for a second when I took my hand off but only for a second. Seems like it is something with the sub, but what could it be? Something loose or is the whole thing shot?
  9. Enkeiavalanche

    Enkeiavalanche Moderator

    Can you take the sub out of the box? Is it ported?
  10. MWright936

    MWright936 New Member

    Box isn't ported. I can take it out. I don't have any more time to mess with it tonight though. What would I look for if I took it out?
  11. Enkeiavalanche

    Enkeiavalanche Moderator

    Wire leads to the sub, Wire from there to the Sub, If you do push down lightly do you hear a scrape sound? Inside the coil of the sub
  12. zigger215

    zigger215 New Member

    The ohm symbol is the upside down horseshoe lookin deal on your meter, touch the one lead to the red terminal on the sub box and the other lead to the black terminal. It takes a lot for a meter to not work...
    Enkie isn't looking for the sub to not "bottom out" when you depress it, he is lookin for a grainy, scratchy, inconsistent feeling when the cone is suspending up and down. What the tells us is if you are having a break down in the motor itself (guts of a woofer). When pressing down on the sub it should have a nice, smooth feelin to it
  13. MWright936

    MWright936 New Member

    Still haven't had time to take the sub out of the box (out of town this past weekend), but when I press on the woofer, it is smooth with no scratchy feeling.
  14. zigger215

    zigger215 New Member

    Hmm yep time to check connection. After you do that, if everything checks out good, we will move on to trouble shooting the amplifier.
  15. MWright936

    MWright936 New Member

    Ok, I finally had time to mess with things. I took the sub out of the box, and all connections are fine. I redid them to make sure. Nothing was loose.

    I'm thinking the sub is definitely the culprit. When I push on it with the stereo off, it feels and sounds smooth. However, when I have the stereo on, and I apply light pressure to either the cone or surround of the sub, it works. When I let go, sometimes it says on for a second or two, but then it will make kind of a rattling sound, and it will cut out. If I keep constant, light pressure on the surround, it stays on just fine. I don't know the inner workings of a sub, but it seems like something in there is knocked loose or broken.

    I'm thinking the amp is fine since it works when I apply pressure. I didn't see any way to take apart the sub to see if I could find what was loose or broken. It seems like I may be stuck buying a new one unless anyone has any further suggestions.

    If I do get a new one, any suggestions? I have been quite happy with my RF. I'm looking for the best "bang" for my buck. Keep in mind, this is just an 8" sub in a crew cab truck, so I'm not looking for anything to blow me away, just to improve the sound of my system.
  16. zigger215

    zigger215 New Member

    Can I get the amp specs?
  17. MWright936

    MWright936 New Member

    I'm not real familiar with car stereo stuff (not even my own), so I'm not sure of the specs. I do know it's a Sony XM-752X. You should be able to Google that and find the specs you're looking for. Hope that helps!
  18. B Cubed

    B Cubed New Member

    As far as I can tell the amp is rated at 75W (RMS) x 2 @ 4ohms, 100W x 2 @ 2ohms and 200W bridged @ 4ohms.

    If I understand your description of the sub above it sounds like the voice coil may have partially separated from the cone. You might try stopping by your local car audio shop and asking their opinion.
  19. Enkeiavalanche

    Enkeiavalanche Moderator

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