Had a good fight this morning with this Sanyo. It came in with intermittent audio and the board under the LA4525 audio IC was darkened. This IC is an 8 pin DIP and uses the pc board for heat sinking. I changed the IC and found out that it was roasting in seconds.
After checking for oscillation and open electrolytics, nothing showed. I checked DC offset at the input, no problem. When I checked the output to the speakers (both) the offset on each was around 3 volts. BOTH output electrolytics were shorted! I removed one and then noticed the trouble! The electrolytics are installed backwards at the factory! Checking with a meter for proper voltage revealed they truly were backwards! Replacing them and installing them correctly makes the IC run cool to the touch!
And another note... the ESR meter was tricked by them being shorted. They weren't "puffed" either!
09-21-2010, 12:42 PM
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