New to power EE. I'm trying to charge up a cap (120 μF) to a high voltage (300 V). I have a tiny transformer that seems to step up the voltage several hundred times (in the 10's of kHz frequency range at least). I am using two NPN bjts (2N4123) to provide a crude clock signal to the base of a PNP (MPSA56) in order to periodically pull down and then block the current through the primary of the transformer (at 14 kHz). When I probe the secondary, I see 100's of volts across the probe impedance. However, when I put a 100 kΩ across the secondary, the voltage drops dramatically. My suspicion is that the transformer is operating very inefficiently. Furthermore, when I do connect a diode and cap in series across the secondary, the voltage charges up on the cap at a very slow rate (a few sec per V). Any suggestions? Are the transistors critical? Do I have to use a MOSFET to operate the primary? Am I running it at too high frequency? Is the duty cycle critical? I decided to use the PNP because I figured the base could be pulled down more robustly than up. I am figuring that the current should be about 100 mA through the primary at about 1 V, so my goal is to see something like 100 μA at the secondary.