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Old 23rd January 2010, 09:24 AM   #1
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Default sansui 9090 (speaker killer!!??)

I have blown 4 sets of speakers (every speaker that i hook up to it) with this sansui 9090.Currently in the dead pool that i seem to keep adding to includes 4 sansui sp-x7's,2 sansui x7000's,and just 5 minutes ago 2 a/d/s l570's. Everyone of these speakers simply stops working with no warning and sounding excellent right before their demise. Could there be something wrong with the amp or should i just put the amp on the shelf and look at it. Everytime the speaker's blow they sound really good with no popping,crackling,or distortion of any sort.Everyone of these speakers have been in excellent to perfect shape boxes and all! This amp simply makes every speaker hooked to it sound better than anything else i've got which include bang and olufson,denon,nad and pioneer.Previous owner of the amp which also bought it brand new confirms my problem so i'm pretty sure i'm not deaf and not hearing them distort. They simply make geourgeous sound then stop all together.Any suggestions on what the hell is going on here? I'm going crazy here!!
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Old 25th January 2010, 11:58 AM   #2
Mooly is offline Mooly  United Kingdom
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Don't think anyone will see this thread here... needs to be in the solid state section.
Perhaps a moderator could move it.

Your speakers. First thing to do is confirm they really are duff... have you tried them on another amp... have you measured the voice coil to see if it is open circuit.

The way an amp destroys speakers is if it has a DC voltage at the output terminals. It would be unusual for a steady "low" voltage to be present causing overheating, but worth measuring anyway. What normally happens is a fault causes full supply voltage to appear destroying the speaker, usually with a loud pop, possible even with the coil catching fire.

So check and confirm the speakers really are dead first.
More unusual problems are instability destroying tweeters.
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Old 25th January 2010, 12:21 PM   #3
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Simply connect a nice big durable power capacitor in series with the speaker (intercept only the red or "+"), and this can block the accidental DC output. This "Output Cap" serves as a speaker protector for temporary use. . . until you have the amplifier repaired properly.
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Old 25th January 2010, 10:40 PM   #4
Vargas is offline Vargas  United States
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Whats actually blowing in the speakers, the crossover, or individual drivers? High frequency oscillation will kill a tweeter for sure.
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Old 25th January 2010, 10:42 PM   #5
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Check for DC or oscillation.
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Old 26th January 2010, 04:25 AM   #6
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i remember some Sansui amps of that vintage having an oscillation problem, and that there was a factory ECO for it. it was a long time ago, so i don't have the info on it anymore, but the oscillation was intermittant and sounded in the speakers like ticking or somebody tapping two wrenches together, so it wasn't a continuous oscillation. another possibility would be the DC correction cap in the diff amp is going bad, and the amp starts out with no offset, but the DC slowly ramps up with temperature or time. those caps would be C05 and C06, they're 470uf/6.3 V caps. i'd change them to 470uf/25V caps if there's room.
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Old 7th November 2012, 04:25 PM   #7
jindra is offline jindra  Canada
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You're blowing your speakers because I'm guessing you've never replaced the capacitors. My 9090 was blowing fuses on my DQ-10's quite often until I replaced all of the caps. Now I can just crank away and nothing blows and sounds very healthy.
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