[Amps] Question about separate power supply/RF section amp

Vic K2VCO k2vco.vic at gmail.com
Thu Jan 17 16:00:07 EST 2013

I'm building an amplifier with a separate power supply. The PS is a unit that sits on the 
floor. I wanted a small desktop amp and there's no room for a rack.

In the power supply section, I have a 0.33 ohm 5W resistor in parallel with a 6A10 diode 
between the negative output of the power supply and the chassis. The idea is that there 
will be 0.5 V across the resistor when the full 1.5 A is drawn from the supply, which will 
be read by the plate meter. The diode conducts at about 0.68 V, so it won't interfere with 
normal currents, but will protect the meter if the current goes much higher.

Now here is my question: suppose there is an arc to ground in the RF section. It will 
instantaneously raise the chassis of the amplifier to a high potential relative to other 
grounded things. The interconnection between the power supply and the RF section includes 
a no. 16 ground wire, the braid of the RG59/U HV lead, and a no. 16 B- lead. The length of 
the cable is 10 feet. The arc current will have to flow through all of this plus 
connectors in order to flow through the diode back to the negative side of the supply.

Is this a safe arrangement? I am thinking of adding another diode from B- to chassis in 
the RF section. I don't see how this could hurt, but it might help clamp the voltage in 
the event of an arc.

Any comments?

Vic, K2VCO
Fresno CA

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