If you're interested in designing a soft start from scratch, I highly recommend going the NTC/thermistor route. NTCs allow you a faster start-up and they handle the peak power better than power resistors do. I write quite a bit on that topic here: The Ultimate Guide to Soft Start Design.
A simple current transformer is easy to turn into a current probe for your oscilloscope: The $10 Current Probe.
Tom
A simple current transformer is easy to turn into a current probe for your oscilloscope: The $10 Current Probe.
Tom
Sometimes it is just the heater wire sticks out the top of the cathode and you see the turn-on surge more with these. There is a surge as the filament heats up and the resistance rises to it's proper level.
Inrush current limiting isn't a bad idea. Several 1960's era amplifiers commonly had inrush limiting. WHat it will do is long term extend capacitor life, along with heater life (but you normally drop in emmision before that is an issue).
Inrush current limiting isn't a bad idea. Several 1960's era amplifiers commonly had inrush limiting. WHat it will do is long term extend capacitor life, along with heater life (but you normally drop in emmision before that is an issue).
Hi Tom,
I haven't seen that yet, but I'm not surprised at all. I strongly prefer E-I core transformers.
Actually, what you said about surge resistors is not true at all. It isn't uncommon for thermistors to burn out, they've been doing that for 5 decades or more! lol!
Size the fixed surge resistor correctly and they do not burn out, very rare event. If the relay fails to close they will. That can be an advantage as it limits other, more expensive damage.
I haven't seen that yet, but I'm not surprised at all. I strongly prefer E-I core transformers.
Actually, what you said about surge resistors is not true at all. It isn't uncommon for thermistors to burn out, they've been doing that for 5 decades or more! lol!
Size the fixed surge resistor correctly and they do not burn out, very rare event. If the relay fails to close they will. That can be an advantage as it limits other, more expensive damage.