Thread: Electric fence

Hey all,

I have been asked by my brother-in-law to look at an electric fence that he bought at an auction (I know big mistake, but he paid $20 so he was happy to take the risk), and of cause it doesn't work. Initially, I said "That's why someone put it in the auction", but then he admitted that he had initially tried using a 12v battery to test it before realising it was running on a 6v battery (it's a solar charged unit). So we are unsure if it was broken to start with, or as a result of using the wrong battery. I was hoping I could get some advice, but firstly let me clarify, I only have a basic understanding of electronics (listened a bit to my father as a teenager, as this was his profession, but unfortunately he has passed away), so please forgive me if I ask some silly questions or make some silly assumptions.

I decided that perhaps as he had doubled the voltage, the manufacturers may have planned for this in the circuit and protected it in some way, so after giving it a few weeks without power to ensure everything had discharged, I had a look at the circuit. From what I can tell (understand), the circuit uses a 1N5342B, 6.8V, 5W Zener Diode to regulate the voltage, and the excess bleeds to ground (this may be one of those silly assumptions I was referring to). Testing the diode with a multimeter, it is open circuit, so excitedly I thought great, just replace the diode and he is back in business. Then the brain started working, and I thought if it had short circuited then yes, but open circuit means the full 12 volts was allowed to flow into the circuit, so this is not good news?

Below is a picture of the front and back of the circuit board (with the diode removed, I have put an arrow to show the location of the diode)

photo 1.jpgphoto 2.jpg

With the diode in position and running on a 6 volt battery the led was flashing as you would expect, but no ticking or and measuring the output with an electric fence tester, no readable voltage is being produced (the 5 light type electric fence testers).

So I guess my questions would be:

* Would him using the 12V battery have resulted in causing the diode to go open circuit, and if so would it have resulted in damage to other parts on the circuit board (I think that's called a cascade failure).

* I need to order the diode online (can't get it at Jaycar), so is it worth replacing the diode (cost about $4 with postage), or should he stop at the $20 he has already spent and bin it.

I realise that it is probably a bit hard without having the circuit board in hand or a circuit diagram, but any help would be greatly appreciated.

Cheers,

Camo