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Author Topic: Help with what to look for when . .  (Read 688 times)

Peter Blair

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Help with what to look for when . .
« on: November 27, 2018, 09:58:14 AM »
Hello, and thank you in advance for reading my post, and/or trying to help out a newbe.
I have a Peavey, KB100 keyboard amp that I'm having a problem with. When I got the amp, it had a burned out transistor, which I have replaced, along with a few obviously overheated resistors. I replaced the filter capacitors for good measure as well. Well, overall the outcome was quite successful except for . . .
As the input signal dies out and becomes very quiet, (in my case, this would be a guitar and/or a keyboard) the signal seem to break up and sound distorted. You wouldn't notice it at normal listening levels, but if you let the note sustain, as the volume decreases the distortion sets in. Maybe better described as "breaking up", more than to call it distortion. I don't know if that's enough information to go on, but can anyone tell me what I might be looking for to remedy the situation? What might be causing it?
Thank you,
Pete

(link to schematic, or see attachment that I tried to include)
https://www.electronica-pt.com/esquema/audio/amplificadores-audio/peavey/peavey-kb100-amp-28103/

Jazz P Bass

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Re: Help with what to look for when . .
« Reply #1 on: November 27, 2018, 11:25:02 AM »
That decaying distorted sounds could be the amp itself (crossover distortion) or the speaker.
Things that you can try:
Another amp into that speaker.
The Peavey amp into a different speaker.

Enzo

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Re: Help with what to look for when . .
« Reply #2 on: November 27, 2018, 06:42:23 PM »
Yes, connect the amp chassis to a different speaker to see if you still hear this.  It sounds to me like you might have a rubbing voice coil.

Peter Blair

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Re: Help with what to look for when . .
« Reply #3 on: November 28, 2018, 09:59:04 AM »
YOU GUYS ARE AWESOME!!!
Hooked up to my Peavey Bandit speaker.
Noise GONE!
The benefit of experience.

Well, I'm glad it turned out to be something so simple. And as luck would have it, I just happen to have a 15" speaker that I got for FREE some time ago, that I repaired and is now working fine. (broken voice coil wire) So now I have a back-burner project of repairing the original speaker. Thank you both for sharing with me, (stated previously), the benefit of your experience. May you and your families both, enjoy a happy holiday season.

Pete

 

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