Help - killed both Cerwin Vega tweeters (or worse) with APM-200?

Discussion in 'Speakers' started by lokerola, Jan 12, 2018.

  1. lokerola

    lokerola AK Subscriber Subscriber

    Messages:
    820
    Location:
    Alexandria, VA
    Fellow AK's,

    We'll I bought and hooked up a used Realistic APM-200. I checked all connections, except I set the impedance incorrectly. Duh. I set it to 4ohms, not 8ohms.

    I turned it on and didn't see a lot of movement on the meters, so I turned it up. The amp clicked off. I freaked out and realized my mistake. I changed the impedance to 8ohms (to match my Cerwin Vega VS-120's), and it all came back on.

    BUT....now neither tweeter is now working. Mids and woofers are OK, but nothing on the tweeters. Is it possible to have blown BOTH tweeters with my ignorance? Is it possible I blew up a capacitor? I don't think I hurt the amp, right? It's still cranking away, but only on the mids and woofers.

    Ugh....any help is appreciated.
     

     

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  2. goodolpg

    goodolpg Just an old fart trying to help. Subscriber

    Those speakers have fuses or circuit breakers?
    How loud was the volume, how high was the treble set.
    EDIT---reading below I see the Realistic is a meter unit, not a power source, so my previous ponderings about DC offset do not apply.

    The speaker troubleshooting is still relevant.
     
    Last edited: Jan 12, 2018
    lokerola likes this.
  3. lokerola

    lokerola AK Subscriber Subscriber

    Messages:
    820
    Location:
    Alexandria, VA
    Funny you should mention that. The speakers never had the fuses installed, and I never scrounged up the right ones to fit.

    I have a multimeter, but I'm not sure which ohm setting I should use to test? There are ohm settings all the way from, 200 ohms, all the way up to 2000kohms. The user manual says to set it to the highest setting. If I set it to 2000kohms, the reading across the tweeters (pulled from the cabs) is 0 (zero). If I switch the multimeter to 200 ohms, I get 3.3ohms on each speaker - which leads me to believe that the tweeters are OK (according to the multimeter).

    I've disconnected the APM and nothing has changed (i.e. mids/woofers good, tweeters get no sound).

    Arg.
     
  4. goodolpg

    goodolpg Just an old fart trying to help. Subscriber

    Use the lowest, 200 ohm or the next one up 2000 ohm.
    The tweeter (two wires) must be disconnected from the speaker crossover to get an accurate reading. Hopefully yours use push on terminals and aren't soldered on.
    Oh boy, no protection, hope they aren't blown.
    Fuses are dirt cheap and worth every cent once you've blown something up.
    I Googled them, it appears there may be some sort of fuse or breaker on the back next to the connection terminals.

    EDIT---I see you have checked them and got 3.3 ohms, they should be good based on that.
    IS IT POSSIBLE they weren't working before?
    If the fuse is inline with the tweeters I don't see how they would have worked before if there were no fuses installed.
     
  5. lokerola

    lokerola AK Subscriber Subscriber

    Messages:
    820
    Location:
    Alexandria, VA
    OK, so on the lowest multimeter setting (200ohms) both tweeters (which are disconnected from the cabinets and on my coffee table), measure 3.3 ohms, which is very close to the 4ohms listed in the specs.

    If I didn't blow the tweeters, what else could I have blown? The crossover or something on the crossover? The amp itself?
     
  6. goodolpg

    goodolpg Just an old fart trying to help. Subscriber

    OK--PROCEED WITH CAUTION---
    Have volume low, treble knob low, bass knob low....you could try hooking the two wires from the Realistic direct to each tweeter.
    LOW VOLUME--- LOW BASS--- LOW TREBLE
    just long enough to see if they produce any sound.
    Do not let the speaker wires touch each other!!
     

     

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  7. Grenadeslio

    Grenadeslio Super Member

    Messages:
    1,670
    Just pulled up the owners manual, the meters will just read incorrectly if the switch is improperly set, no damage will result. Try connecting the speakers without the APM connected and see if the tweeters work without the unit installed, might just be killing the high frequecies.
     
  8. toddalin

    toddalin Super Member

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  9. lokerola

    lokerola AK Subscriber Subscriber

    Messages:
    820
    Location:
    Alexandria, VA
    Nope. I removed the APM speakers wires from back of the amp and no bueno - no tweeter sound at all from either speaker.
     
  10. lokerola

    lokerola AK Subscriber Subscriber

    Messages:
    820
    Location:
    Alexandria, VA
  11. goodolpg

    goodolpg Just an old fart trying to help. Subscriber

     

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  12. toddalin

    toddalin Super Member

    Messages:
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    I would suggest that there is a possibly a problem with the amp and switching it to 4 ohms possibly put dc to the speakers possibly taking out components/drivers.

    I have four VS-110s for surrounds, now with JBL components, and I don't recall any fuses when I removed the old guts from the cabinets.
     
  13. lokerola

    lokerola AK Subscriber Subscriber

    Messages:
    820
    Location:
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    OK - that worked! Both tweeters are operational using this method! Awesome. Except they don't work in the cabinets!!

    Thoughts???
     
  14. lokerola

    lokerola AK Subscriber Subscriber

    Messages:
    820
    Location:
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    Looks like the tweeters are good outside of the cabinets. Ohm meter gets 3.3 and when I hook up speaker wire to each lead I get sound on both tweeters. Something seems wrong with the crossover? or cabinets?
     
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  15. goodolpg

    goodolpg Just an old fart trying to help. Subscriber

    OK, now we're getting somewhere...
    can you access the fuses?
    If so, check the fuses with the ohm meter the same way you did the tweeters. Disconnected and 200 or 2000 setting.

    Odd the tweeter in both speakers quit, that's got me scratching my head since they work ok when hooked directly to the source.
     
  16. lokerola

    lokerola AK Subscriber Subscriber

    Messages:
    820
    Location:
    Alexandria, VA
    No fuses. I got them without fuses, couldn't find the right ones, and stupidly just ran them without the fuses (successfully, for like the last year).

    Is it possible to somehow use the multimeter to test the unhooked wires for the tweeters hanging out of the cabinets? Maybe I blew a capacitor (if that's even possible?)
     

     

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  17. goodolpg

    goodolpg Just an old fart trying to help. Subscriber

  18. Grenadeslio

    Grenadeslio Super Member

    Messages:
    1,670
    You are absolutely right, there shouldn't be any output with the fuses removed, unless someone was in there screwing with the works.

    And if they are working without the fuses then someone has definitely been monkeying with the crossover, and who knows what they screwed up. But with the help of that simple wiring diagram it should be easy enough to see where the trouble is.
     
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  19. awillia6

    awillia6 Super Member

    Messages:
    1,058
    You don't need no stinkin' fuses; the speaker drivers will protect the other, more delicate components...
     
  20. lokerola

    lokerola AK Subscriber Subscriber

    Messages:
    820
    Location:
    Alexandria, VA
    They've been cranking away (loud) for the last year with no fuses. Now, I will say the PO said he re-foamed them, and re-capped them. The foam is nice, but I've never cracked them open to see what he did to the caps and speaker wiring. Ugh....
     

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