Lepy LP-2020A Other Mods

After just one week, I decided to get te screwdriver out and do some more modifications to the Lepy LP-2020A. Here are just some of the changes made.

Removing Transistor Q4

A small circuit consisting transistor Q4 regulates the power for the operational amplifier ICs. When I measured its output voltage, it was only around 5.5 V which is woefully small. My impression was that the transistor must be faulty as it was also getting warm, hence I removed it completely. According to the documentation, the JRC4558 operational amplifiers can operate on 12 V very easily, hence I removed the transistor and bypassed it with a small blob of solder by connecting the two pads showin by the red line. Now my op amps are operating on 12 V, and I also increased the smoothing to their supply planes with larger capacitance.

Power Supply Capacitor Change

Since I am making the power amplifier IC operate close to the supply rails, it stands to reason that the nearby reserve power is sufficient, hence increasing the specification of some of the electrolytic capacitors should help.

Bigger Capacitors

The green-coloured (SAMXON) 100 µF/16 V electrolytic capacitors were replaced with blue-coloured (JB) ones with value 330 µF/25 V. The main power supply capacitor was also replaced with ELNA 15000 µF/16 V.

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