[Amps] Rectifier equilization?

[Vic K2VCO]

Absolutely correct! I learned this the hard way when I accidentally shorted the screen to 
ground in my 813 amplifier. Poof, no more screen meter, despite back-to-back diodes.

On 9/14/2013 8:12 PM, Bill Turner wrote:
> ORIGINAL MESSAGE:          (may be snipped)
>
> On Sat, 14 Sep 2013 19:13:02 -0700, Jim wrote:
>
>> also use the 6A10 as a safety diode
>> across meters.
>
> REPLY:
>
> A diode across a meter provides almost zero protection. One must put an
> appropriate value resistor in series with the meter and place the diode
> across both the meter and resistor. Perhaps this is what Jim meant to say?
>
> Diodes such as the 6A10 and its cousins don't conduct until the voltage
> across them reaches about .6 VDC. By the time the voltage across the meter
> reaches that, the meter is already destroyed.
>
> Choose a resistor value such that the voltage across the meter + resistor
> will reach .6 volts at about 110% of full scale current. At that point the
> diode will conduct and shunt any current above that.
>
> In nearly all circuits, the resistor value is so small it has essentially no
> effect on the rest of the circuit. Cheap insurance.
>
> 73, Bill W6WRT
> _______________________________________________
> Amps mailing list
> Amps at contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
>

-- 
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco/