Leader 1507A Repair (3-51FT-A Replacement)

This digital signal generator was stored for too long time and the internal battery was leaking and corroded the PCB near by.  After removing the battery (Nicad 3-51FT-A) and cleaning the PCB, power on test show that there was no display on the front panel.  One 1k resistors was also replaced in the charging circuit and put back a 3.7V 110mAh Ni-Polymer rechargeable battery, but the set still could not power on.  Note that the battery was got from ebay China seller with only SGD$0.9 and free shipping!  It is a 110mAh capacity and the original batter is 80mAh capacity.

After measuring the rail voltage, it was find that the two 5V supply after the regulator JRC 7805A was not at normal voltage, one close to zero and another one 4.5Vdc. Replacing the two regulators with Toshiba 7805S regulator and the set is back to normal.  Here are some photos for the repaired set.

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