50W Stereo Kit amp runs for 1 min, clips then turns off. - Page 2 - diyAudio
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Old 3rd March 2012, 06:45 AM   #11
Al600 is offline Al600  Australia
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I've fixed the capacictor and all was well for 2 minutes but then the same problem happended. I was so sure that was it. Any more ideas?
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Old 3rd March 2012, 06:53 AM   #12
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Quote:
Originally Posted by Al600 View Post
I've fixed the capacictor and all was well for 2 minutes but then the same problem happended. I was so sure that was it. Any more ideas?
ok. now let's do this:
Remove power to the right channel and turn it on (one channel only)
that way you can trace the channel that is causing the problem.
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Old 3rd March 2012, 06:56 AM   #13
Nrik is offline Nrik  Denmark
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The wrongly polarized electrolytic is probably not reason for the failure - althoug it should still be fixed.
From the description it sound more like the amp going into oscillations and then goes into protect mode.
To prevent that, you might want to parallel the 22k feedback resistor with a 50pF capacitor maybe in series with another 22k resistor.

Check out testcircuit 2 on page 5:
http://www.ti.com/lit/ds/symlink/lm3886.pdf

You can solder this to the underside of the PCB on the two leads on the 22kohm resistor.
edit: I would just use the 50pF or 47pF capacitor directly parallel over the 22k feedback resistor
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Old 3rd March 2012, 06:56 AM   #14
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"0 volt from power supply" should go to "speaker ground" right channel
I do not see ground on the right channel!!!

Last edited by lanchile; 3rd March 2012 at 07:00 AM.
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Old 3rd March 2012, 07:09 AM   #15
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Al600! did you put the GROUND WIRE to the right channel already?
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Old 3rd March 2012, 07:12 AM   #16
Al600 is offline Al600  Australia
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Just tested it then. Same problem I'm afraid.
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Old 3rd March 2012, 07:16 AM   #17
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Al6000 could you measure the dc resistance of the speakers you are driving? with 35V rails you should really not be running less than 8 ohm speakers.

for a nominally 8 ohm speaker you may get a reading of perhaps 6 ohms across the speaker terminals.

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Old 3rd March 2012, 07:20 AM   #18
Al600 is offline Al600  Australia
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Looks to be 7.7ohms.
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Old 3rd March 2012, 07:22 AM   #19
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Just tested it then. Same problem I'm afraid.
I saw the connections No ground from "0 v" to modules.
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Old 3rd March 2012, 07:24 AM   #20
Al600 is offline Al600  Australia
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So I added another cable from speaker ground to 0V. The problem has persisted.
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