[Amps] Rectifier equilization?
Vic K2VCO
k2vco.vic at gmail.com
Sat Sep 14 23:31:13 EDT 2013
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
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--
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco/
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