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Old 2nd May 2011, 04:05 PM   #1
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Default Mission 770 scratchy sound

Friends

I have recently bought a pair of mission 770 speakers and am experiencing some problems. I get a scratchy sound from one of the speakers at a certain point of listening: this is at reasonable volume and with a variety of music. Its irritating and is more prevalent on one channle. Not sure iots the driverr or crossover or just age.

Not ready to retire them as they are really nice and have potential in a second system. Cabs look good and drivers seem to be in good nick

Please advise or provide tips I might try to restore them to normal use

Thanks
Christowp
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Old 2nd May 2011, 07:11 PM   #2
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Disconnect the scratchy speaker from the amp and carefully push on the cone to see if you can feel the voice coil rubbing. Slowly and carefully push the cone in the full travel and if you can feel and hear the voice coil rubbing you know it is the driver. If you feel and hear no rubbing then the problem is else where and you will have to pull the driver to inspect the cross over and driver. Considering how old those speakers are there is a good chance the problem will be in the cross over if you do not fell or hear any rubbing.
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Old 2nd May 2011, 07:19 PM   #3
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Default Missions 770 scratchy

Thanks Andy

Will try that when I get home from work tomorrow - Christowp
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Old 5th May 2011, 07:11 AM   #4
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Default Scratchy speakers: Mission 770

Andy

Drivers clear and no noise or vibration when moving them: will check crossovers and also replace fuses over the weekend

Thanks

CR
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Old 5th May 2011, 07:00 PM   #5
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You may want to think about replacing the capacitors in the cross over while you have them out. They are very old to say the least and there is a good chance they are electrolytics. Swapping them out for newer much better quality can only help. The inductors wouldn't hurt either but the caps are most important.
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Old 6th May 2011, 07:23 PM   #6
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A scratchy sound developing is often because of amplifier bias setting trimpots drifting with age.
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Old 6th May 2011, 07:25 PM   #7
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Maybe swap the speakers around to confirm you aren't hearing static on your volume pots.
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Old 5th June 2011, 09:32 AM   #8
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Default Hope I can help...

Dear Christowp,

I hope I can help you because I have registered solely for that purpose! I have owned a pair of beautiful Mission 770s since 1982. I bought them in Cambridge, England, near where they were made. This was with my first pay cheque from Cambridge University.

The right speaker started making a scratchy sound 2 weeks ago. Given how old they are, I wondered if "this is the end". However, I have just flicked the solder and glue blobs on that woofer and behind the driver (which is semi-transparent) I could see a small washer "dancing around" and buzzing against the solder on the inside. I picked up the entire speaker in its housing, inverted it and the washer went up the wire and stayed there. No more scratchy sound.

Obviously a more permanent fix may be needed, but for now I am enjoying unblemished sound.

I really hope you have the same issue -- very easy to fix.

Warmly for tropical north Queensland,

Richard.
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Old 8th July 2011, 11:19 AM   #9
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Default Mission 770

Dear Rasquire

Thanks for your reply: just received speakers from speaker compnay: soldering was loose on both bass drivers. This was re done and sound is really good now, no more scratching. Tech feels the internal wiring is unneccesarrily thick and inflexible.

Until next "injury" I am enjoying good clean and detailed sound again.

rEGARDS

Christo
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