Stevens power supply

[Tom]

Does anyone have information on the Stevens power supply used with the early testers? I have on thats putting out 17 volts under the load of a 12V light bulb. Is that normal? How could it be correct as a power supply for something that’s supposed to use a 6 volt battery?

Tom

[frankr]

Time has dulled the senses, but I’m thinking it was supposed to be used WITH a battery. But maybe I’m confusing it with the Eisemann tester which I also used to have.

[Tom]

Frank, that would make sense. But the manual says to hook it right up to the tester and doesn’t mention a battery in that section. Interesting… I even replaced the full wave rectifier in there with a diode and still got too much voltage. I’m wondering if this originally had a vacuum tube rectifier that wasted a lot of voltage.

If anyone can show a photo of the inside of one of these, that might help.

T

• This reply was modified 3 years, 11 months ago by Tom.

[frankr]

Actually, come to think of it, as I recall, the Stevens had a huge filter coil and capacitor to remove AC ripple, so it probably did not use a battery.

[frankr]

More thinking about it, (thanks Tom), does it really matter what the voltage sent to the tester is? Doesn’t the Stevens tester vary the voltage sent to the coil by a user-controlled rheostat? Isn’t that how the thing works?

I’ll probably be pondering this while lying awake tonight.

[Tom]

Frank, It’s the amperage that’s varied by the rheostat. The first component that sees the DC voltage is the vibrator tube, and I have to imagine there’s a limit to what the little coil in there can take. Everything else in the coil test circuit is rated for a lot more.

I might try half wave rectification with a few diodes in series to waste some voltage. Half wave with the load of a small light bulb got the voltage down around 8.5V.

Thanks for your input, all ideas are appreciated!

Tom

• This reply was modified 3 years, 11 months ago by Tom.

[jeff-register]

Tom,
I have found with power supply’s that almost always the output is higher at static load, then at load test depending on transformer to load ratio the voltage & current have change.
Then costs of manufacture a smaller step down the less the costs & designers are inclusive. If you have bridge rectifier depending how it’s made silicone or later also adds to the variables of output. Then consider the parameters of output that are acceptable per design.

[dave-bernard]

the merc o tronic vibrator is 7.5 v if that helps.

[frankr]

Tom, you are correct that I did not consider the vibrator and the voltage it can withstand, so that is a good question. However, and I think you already know this, the amperage is a direct result of the voltage drop across a resistor (the rheostat). I-E/R, E=IR, and all that stuff.

[Author]

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