Is the brown stuffs glue? - diyAudio
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Old 27th June 2013, 04:14 PM   #1
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Default Is the brown stuffs glue?

Is the brown stuffs glue? It kind of looks like the liquid from electrolytic capacitors, except there is no electrolytic capacitors around it.

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Old 27th June 2013, 04:15 PM   #2
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Yes, and in (some) applications it can be troublesome becoming conductive with ageing.
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Old 27th June 2013, 04:43 PM   #3
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For some unknown reason, this amp won't start any more. My guess is one of the channel has DC offset which triggered the speaker protection relay. Does amps built with glue like this known to stop working when aged because the glue start to conduct?
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Old 27th June 2013, 04:50 PM   #4
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Have you measured for a DC offset ?

Whether the glue is an issue or not is impossible to say without you faultfinding on it but glue has been an industry wide issue in older equipment (more so TV/Video than audio).

It wouldn't be the first suspect... you need to do some basic checks and see why the relay is tripped if that is the problem.
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Old 27th June 2013, 05:13 PM   #5
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I have managed to isolate the problem to one channel, but I have not been able to measure the DC, the spot is hard to reach without taking everything apart.

For some reason, the amp starts instantly now. I have not been able to make it not start at the moment, so I can't make any measurement until the problem comes up again.
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Old 27th June 2013, 06:01 PM   #6
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It may be nothing more than a dry joint somewhere. Output, drivers and regulators are favourite trouble spots.
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Old 27th June 2013, 06:09 PM   #7
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The amp is a about 20 years old now, the problem only shows up often recently (only rarely in the past). Would a bad joint worsen only after all these years? My guess is it's an age related problem, I thought it was electrolytic capacitor drying up, but not so sure now.
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Old 27th June 2013, 06:23 PM   #8
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Joints worsen with age and heat cycle stress. This is typical,
Click the image to open in full size.

Click the image to open in full size.


Do you see how the solder is cracked around the leads
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Old 27th June 2013, 06:30 PM   #9
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I see, you just gave me a bit of hope that I won't need to do anything drastic. Thanks a lot.
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Old 27th June 2013, 06:33 PM   #10
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Your welcome
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