05-04-2017, 10:51 AM
Not normal at all. Some regulators will run quite high when totally off load but once you've got a small load on it it should drop no more than a few millivolts from there to full load. So try 100R load and see what happens.
If the voltage drops significantly from 100R load to 5R load then what could have gone wrong? One likely reason is that the troughs of the input DC are dipping below the dropout voltage of the regulator. As you increase the load the troughs get deeper as the reservoir cap discharges more before it gets recharged at the next peak of the mains. The remedy is a higher voltage transformer, bigger reservoir cap or possibly using lower drop (schottky) rectifiers.
If the voltage drops significantly from 100R load to 5R load then what could have gone wrong? One likely reason is that the troughs of the input DC are dipping below the dropout voltage of the regulator. As you increase the load the troughs get deeper as the reservoir cap discharges more before it gets recharged at the next peak of the mains. The remedy is a higher voltage transformer, bigger reservoir cap or possibly using lower drop (schottky) rectifiers.
www.borinsky.co.uk Jeffrey Borinsky www.becg.tv
