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Dried glue on circuit boards can cause some bad things to happen. I have seen corrosion on leads where they come in contact with glues from a variety of manufactures. This is almost always minor, and can be brushed or flushed off with solvent. I have never seen it affect the operation of the amplifier, let alone casue a failure.
Sansui on the other hand is another story. The formula they used for their glues is notorious for causing all kinds of chaos. The following photos are an example of what I often see in Sansui units. This is damage on the power supply board of an AU-717. The unit had a channel that had failed. |
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Some of the dried glue has been removed from the board (above - you can see the milky ring where the glue was). Every lead in contact with the glue is corroded. The green color indicates copper oxide. I am no chemist but I believe that the glue becomes conductive, creating an electrolyte that allows a current flow accross the board. This sets up a condition for electrolysis to occur between the copper core of the lead and the silver/lead tinning.
Below, I have outlined where the glue has been removed. The lead had eroded clear through and caused the failure of the channel. There were several resistors that were near failure like this in this amp. |
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Some different
angles of the same resistor.
I have lifted the end of the resistor off the board here... |
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