I am trying to get 5v DC by rectifying the output of a microwave transformer i rewound (the transformer gets approx 4.2V AC on the secondary winding). I managed to get approx 5V open circuit voltage on the DC side of the rectifier but as soon as i connect a small load (tiny 6v test light which can be seen on the photos) the voltage drops from 5v to approx 4.3 volt; the AC voltage on the secondary winding of the transformer barely changes when connecting/disconnecting the light bulb). Also the voltage drop over each diode is approx 1.5v (which confuses me since i thought it should always be 0.7volt). The measurements can be seen on the photos. I have also tested with a different load (18650 charge controller ic) which gives approximately the same results. I have tried using 10A10M10 diodes bit that also gave the same results.
I am using IN4004 DC Diodes. I am using a 25v 2200uF capacitor for smoothing out the dc output (I also tried with a 4700uF cap). The capacitor is in parallel with the load as can be seen in the schematic. Is this sort of voltage drop normal? Is there anything i can do to prevent it? Have i made a mistake somewhere in terms of circuitry or component choice? Any input is greatly appreciated. Thank you very much!