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[Amps] Grid current protection HELP

To: "" <>
Subject: [Amps] Grid current protection HELP
From: rick darwicki <>
Reply-to: rick darwicki <>
Date: Mon, 13 Feb 2012 16:59:07 -0800 (PST)
List-post: <">>
Hi all,

A while back K6XX published an article that can be found at 
It is a simple opticoupler that triggers a 555 timer base on the voltage drop 
across a resistor.
I built the circuit but only connected pin 2 to the 100k resistor from the 
It has different levels of working with different connections I have tried. 
Grounding the relay jack will key Q1 if the output is low, but it starts high. 
At one point I could vary the voltage in to the opticoupler and trigger the 
555. Also, the time delay worked too. Now I can't get it to do much hi hi I 
need to start over.

I'm a tube and voltage guy and almost nothing I've built SS except for a 160 
meter surface mount SDR and my copy of the Alpha 78 QSK board has worked first 
time out hi hi

Can someone look at the schematic and let me know what the problem is, IE 
correct it? 
I can see the trigger tied to B+ and do not think that is correct.  
I assumed pin 4 needed to go to B+, maybe not.

I made a PCB and it is a pain makeing changes and cutting foil.

Please, any help from you solid state guys? My 8874s need you. K6XX does not 


Rick, N6PE


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