Hi Bill,
Use a 2000-3000 mfd cap accross the coil, and a 500 ohm series resistor.
Use two 25 ohm power resistors, one in series with each side of the line.
The 500 ohm resistor can be adjusted to give the desired amount of delay.
You only need enough delay to allow the HV meter to come up to 75% of
normal voltage. 3-4 seconds is OK, but probably not necessary.
I have built over 30 of these, and they worked every time!
GL!
Phiul, K5PC
>
>I'm in the process of building the power supply for my amp project. I am
>having problems getting the correct delay in the step start circuit. I
>decided to use the same circuit as the amp project by G. Daughters, K6GT,
>that appears in the most recent ARRL handbook.
>
>I am using a 24 V DC relay that has a coil resistance of approx. 280 ohms
>(Rcoil) and I want to get about a 3-4 second delay in the RC circuit. When
>I got all the parts together I knew the circuit wouldn't work just looking
>at the values, so I mocked it up and it indeed didn't work.
>
>The circuit consists of a diode (D5) and 3.9k resistor (R13) in series
>connected to the coil of the 24 VDC relay with a 600 uf capacitor (C11)
>connected across the coil of the relay. 120 volts AC is connected to this
>circuit. This circuit is basically a half-wave rectifier and R13 and the
>Rcoil act as both a voltage divider and resistance for the RC time
>constant. I am only getting about 4 volts across the coil where this relay
>needs a minimum of about 14-15 volts to kick in. This makes sense looking
>at the circuit equations:
>
> Vcoil = Vin * Rcoil / ( R13 + Rcoil ) ~= 55 * 280 / (3900+280) ~= 4.0 V
>
>where Vin was measured and is about 0.45 * 120 volts which makes sense for
>a half-wave rectifier circuit.
>
>Am I doing something really stupid and missing something?
>
>73s
>
>Bill, W6QD
>
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