Amp stopped working. Any ideas?

Discussion in 'General Electronics Chat' started by stupidlogic, Dec 10, 2010.

  1. stupidlogic

    Thread Starter Member

    Aug 10, 2010
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    I have a Logitech Z-5500 speaker system (just so you're familiar with what I'm talking about) and the breaker was reset when it was plugged in and blew the fuse in amp. This happened to both my and my roommate's systems (we both have the same setup). He couldn't find a replacement fuse in town so wrapped foil around it and stuck it back in and his system works fine. I got new fuses and it keeps blowing them immediately after turning it on. So then I tried the foil trick to see if I might have the wrong fuses and to see if it would work at all. it turns on and hums, but doesn't completely power on correctly and gets very hot very fast. So I am thinking there is a short somewhere and it's drawing a lot of current; I'm just not sure where to start looking for a short. What would be most likely, etc.

    Any suggestions would be helpful. Thank you!
     
  2. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    bypassing the fuse probably caused more of your output electronics to be damaged. Fuses blow to protect things from 'getting to hot', and various other destructive scenarios. After telling me you bypassed a fuse and turned it on again, I personally would direct you to Ebay, or BestBuy at this point.
     
  3. beenthere

    Retired Moderator

    Apr 20, 2004
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    If you have a meter (pull the fuse and get rid of that foil first), start checking for shorted transistors. Look for bulged and popped open capacitors.

    As Kermit2 said, you caused more problems with the fuse business. You may find partially melted wire insulation on top of bad components.
     
  4. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    You may be able to save it, but it may be cheaper to buy a new set.

    We would need photos of the PCB, and even then couldn't guarantee good help.

    It may be obvious, such as something went up in smoke, etc. It may not be obvious.

    I'm unsure of your abilities in electronics and troubleshooting, as there will be surface mount devices to check and work with on this.

    P.S. The foil wasn't a good idea. ;)
     
  5. stupidlogic

    Thread Starter Member

    Aug 10, 2010
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    Yeah, I wasn't thinking. I was just thinking "oh well the foil worked in my roommates so I can see if that works". I should know better I'm in my second year of studying to be an electrical engineer. So my skills at troubleshooting aren't that high yet but I know electronic components and whatnot pretty well. I have a digital multimeter and then access to all the equipment at school if i need to look at things. So i'll get pics of the PCB and check over the caps and transistors. Thanks for the help.
     
  6. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    Well, skip the images of the board.

    Just found this thread on Another Forum which is titled "Hacking the Z-5550".

    Reports from that thread indicate that most components have their identification marks sanded off, and glue over other components.

    Your roommate may want to try a standard size fuse, otherwise the next hiccup will have him purchasing a new set.

    For $285, I'd go a different route than logitech, such as a "mini home theater in a box". That way you have a spare DVD player, tuner, and a preamp for MP3 players, games like xbox or PS3, and whatnot. For roughly $100 more.
     
  7. stupidlogic

    Thread Starter Member

    Aug 10, 2010
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    Yeah, that was actually my plan if I couldn't get this working. Then I'd have the seperate components and stuff, but I tell you think logitech set is nice. I've had it for while and they have great support. I broke a speaker by dropping it in the first week and they sent me a new one no questions asked and without shipping the broken one back.
     
  8. tom66

    Senior Member

    May 9, 2009
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    Is it still under warranty?
     
  9. stupidlogic

    Thread Starter Member

    Aug 10, 2010
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    No its not. I've had it for about 5 years so the warranty is up. I wish it wasn't up though because they have really good service. In the first week I had it I dropped a satelite and broke it. They sent me a new one no questions asked and without requiring me to send back the broken one.
     
  10. retched

    AAC Fanatic!

    Dec 5, 2009
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    You are a second year EE student and you used foil for a fuse?

    Dont you know foil is for chewing, not fuse replacement?
     
  11. tom66

    Senior Member

    May 9, 2009
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    Then take a picture of the board. You might be luckily and it's a single passive component or two burnt out, but more likely you've blown the monolithic amplifier IC (which contains all the power stage and a lot of preamp stuff) which is either difficult/impossible to find or very expensive.
     
  12. stupidlogic

    Thread Starter Member

    Aug 10, 2010
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    Yeah I know. Lapse in judgement. I was just like "oh it worked for my buddy so ill try it."
     
  13. whatsthatsmell

    Active Member

    Oct 9, 2009
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    Retched - you chew foil???!!! You are the man!:cool:

    BTW - what do you do with the gum? :confused:
     
  14. retched

    AAC Fanatic!

    Dec 5, 2009
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    I use if for structural support adhesive... DUH!

    (Im a second year Structural Engineer)

    KIDDING! Im always glad to see a new name here. So Welcome!

    This reminded me of a Snopes/mythbusters story about the hunters who blew a fuse in their truck and replaced it with a .22cal round.

    After a minute of driving, the bullet fired, hitting the driver in his "baby maker".
     
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