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#1
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"flashing" the gain on a power amplifier question
We have an Alesis Matica power amp used for non-critical listening in a
computer lab environment. It exhibits the following problem: every once in a while the left side goes out and will come back only if you quickly crank the left side gain knob. It's like it needs to be "blown" out, kind of like the "italian tuneup" for cars. What causes this and how can it be fixed? By the way - everything else in the signal chain has been swapped and ruled out as problematic. Thanks, Dan Fox Zumix, Inc |
#2
Posted to rec.audio.pro
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"flashing" the gain on a power amplifier question
In article . com,
Daniel Fox wrote: We have an Alesis Matica power amp used for non-critical listening in a computer lab environment. It exhibits the following problem: every once in a while the left side goes out and will come back only if you quickly crank the left side gain knob. It's like it needs to be "blown" out, kind of like the "italian tuneup" for cars. What causes this and how can it be fixed? Look for leaky coupling caps and cold solder joints around bias resistors. What is happening is that the DC level on some stage's input is floating around, and eventually it rises or drops to the point where the stage turns off completely. Applying a high signal level temporarily fixes it. Also clean the pot. I'm assuming it's not a dead spot in the pot, although that does sometimes happen. By the way - everything else in the signal chain has been swapped and ruled out as problematic. My personal feeling is that this amplifier is not worth your time to fix it, but I am not impartial. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
#3
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"flashing" the gain on a power amplifier question
"Daniel Fox" wrote ...
We have an Alesis Matica power amp used for non-critical listening in a computer lab environment. It exhibits the following problem: every once in a while the left side goes out and will come back only if you quickly crank the left side gain knob. It's like it needs to be "blown" out, kind of like the "italian tuneup" for cars. What causes this and how can it be fixed? By the way - everything else in the signal chain has been swapped and ruled out as problematic. The gain pot itself? |
#4
Posted to rec.audio.pro
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"flashing" the gain on a power amplifier question
Scott Dorsey wrote:
Daniel Fox wrote: We have an Alesis Matica power amp used for non-critical listening in a computer lab environment. It exhibits the following problem: every once in a while the left side goes out and will come back only if you quickly crank the left side gain knob. It's like it needs to be "blown" out, kind of like the "italian tuneup" for cars. What causes this and how can it be fixed? Look for leaky coupling caps and cold solder joints around bias resistors. What is happening is that the DC level on some stage's input is floating around, and eventually it rises or drops to the point where the stage turns off completely. Applying a high signal level temporarily fixes it. Also clean the pot. I'm assuming it's not a dead spot in the pot, although that does sometimes happen. By the way - everything else in the signal chain has been swapped and ruled out as problematic. My personal feeling is that this amplifier is not worth your time to fix it, but I am not impartial. I've met a similar problem with Cret PL series amps, and traced the problem to oxidation of the chip-pins-to-IC-socket scene. Removing and replacing thge chips with a blast of Caig in between fixes it, until next time. -- ha |
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