> I have been playing with an smps a friend built which is supposed to be > identical to Nick Desmith's board > > http://desmith.net/NMdS/Electronics/NixiePSU.html > > with the exception that its a through hole board rather than smd. Im an > audio guy btw not a nixie builder. With a 12ax7a at 300v/1ma it works well. > Noise free, stable, sounds great. But when I tried it with a circuit that > drew 20ma of current, both the voltage and current output collapsed to > 78v/4ma. I tried changing the resistor that sets the output voltage to 200v > and got similar results. Im using a 9v 3amp wall wart supply. I know its > impossible to really diagnose anything without a circuit which is the next > thing Im going to come up with, but I thought it couldn't hurt to post this > and see if there is anything obvious those of you much more familiar with > these supplies than me, might suggest as possibly the problem or what to look > for.
Does the switching FET get hot? If so, you probably need a lower resistance one. What's the DC current rating on the inductor? The efficiency and effectiveness of these single-inductor boost supplies starts to really fall off at large voltage ratios (like you'd have with 300V out). You might consider going to 24V or more on the input side (with appropriate modifications to correctly power the control chip), using a transformer, or adding a voltage doubler. - John -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send an email to [email protected]. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/4FE1F73E-7E98-4537-B4BE-64231C285211%40mac.com. For more options, visit https://groups.google.com/d/optout.
