I want to build up a small, SE EL34 amp on the bench and I have one of those Ebay SMPS. Output 150V to 450V, 50mA to 100mA current out, 6.3V to 12V for heater. Is there a way to slow start it, like a light bulb limiter? Thanks.
Yes
There are solutions available online like eBay and more. You want a thermistor, not a resistor, and a relay to close the circuit so that you don't run on the thermistor after the start sequence.
There are solutions available online like eBay and more. You want a thermistor, not a resistor, and a relay to close the circuit so that you don't run on the thermistor after the start sequence.
You can use RC filter to do this - with a lot of C it will ramp up more slowly. Size the R so the power supply doesn't cut out on over-current. Yes you'll lose a bit of voltage across the R, but that's not unusual for a valve supply.
Downside is there's more energy to drain through a bleeder resistor, and there's more energy to do damage if there's a circuit fault.
Why do you think a soft-start is necessary? For testing?
Downside is there's more energy to drain through a bleeder resistor, and there's more energy to do damage if there's a circuit fault.
Why do you think a soft-start is necessary? For testing?
That's all it is. Testing. Normally I will use a light bulb limiter for a ss amp or a variac for a tube amp when I first scrap them together on the bench. Plus, I've never used am SMPS as a psu before.