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

Vic K2VCO k2vco.vic at gmail.com
Fri Jan 18 14:52:40 EST 2013

Thank you. I think I will use an additional diode, or two as W6WRT suggested. Yes, I 
always use a 20-ohm glitch resistor, which I put in the amplifier. The power supply has a 
pair of 15A breakers. The diodes are 6A10's so they are pretty husky.

On 1/17/2013 5:59 PM, TexasRF at aol.com wrote:
> Hi Vic, as you say, installing another diode inside the amplifier can't
> hurt so why not?
> The only downside that comes to mind is that the added diode could be the
> one that fails due to an arc and might be more work to replace than one in
> the  separate power supply.
> You no doubt have included a B+ surge resistor in the amplifier or the
> power supply to limit fault current. With a well chosen primary fuse size one
> would hope the diodes would be protected from an over current failure.
> 73,
> Gerald K5GW
> In a message dated 1/17/2013 3:35:11 P.M. Central Standard Time,
> k2vco.vic at gmail.com writes:
> 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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