Hi everyone. I’m having capacitor issues on a 12v electric fence energiser. Trying to find out ratings of said caps that are no longer available and matching them is giving me a headache. Some bright spark has glued these blue caps to the board and I’m getting some odd reading in situ. Any ideas on their specs? Not having much luck googling.
Thanks in advance.

 

Appear to be 3.3uF (400v?) I would replace with WIMA MKP4, these are rated for high voltage, high current.
Are you sure the caps are bad?

 

Appear to be 3.3uF (400v?) I would replace with WIMA MKP4, these are rated for high voltage, high current.
Are you sure the caps are bad?

No I’m not sure max. But others are bad including this one which I am in the process of replacing.
The blue ones are showing reading of 6.7! Mmmmm

 

No I’m not sure max. But others are bad including this one which I am in the process of replacing.
The blue ones are showing reading of 6.7! Mmmmm

Mind you, would that be right as they are “wired together”?

 

If the one you show in post #3 then it appears to be electrolytic, they dry out with time.

 

If the one you show in post #3 then it appears to be electrolytic, they dry out with time.

Appreciate the diagnosis

 

I have some 2.2uF 750V caps that look the same in my hand. I think I got them from Digikey.com. I see they do not have any now.
digikey That exact part.
3.3uf 400v parts of many types.
mouser.com 3.3uf 400V film caps.

 

Take full pictures of both sides of the pcb, then we can reverse engineer it.

 

Take full pictures of both sides of the pcb, then we can reverse engineer it.

I’d like to beef it up a bit as we’re only getting 3000v and 0.7 j. Large cap not attached.
Hoping the new 20uf 450v starter cap will improve performance. Maybe I should have gone with a 25uf?

 

Looks like it's a 556 dual timer , pulsing a transistor, i see you've removed it from the pcb is it faulty?

 

it's likely not a job offer

 

Looks like it's a 556 dual timer , pulsing a transistor, i see you've removed it from the pcb is it faulty?

It was indeed faulty. And the bloody spade connector came with it.

 

If you want to get bigger pulses from the same system you need to fill in more of the positions where the blue capacitors are mounted. But then you will need to use a transistor switch with greater current handling capability. So the output can be increased but the effort is not super simple.

The failure that I have come across in fence chargers, with one exception, is a break in the secondary winding connector, usually deep within a winding section. That is easily but not simply repaired bu unwinding the wire onto a spool until the break is reached, patching the break, and then rewinding the wire. This requires a fixture to achieve, not hard to produce, but rather tedious to build.
Once the word gets out that one is able to repair fence chargers there are quite a few folks who want theirs fixed.
I have wondered if an older automotive spark ignition transformer would be effective, but I have never tried to see if it would. That could be an exciting experiment.

 

I have wondered if an older automotive spark ignition transformer would be effective, but I have never tried to see if it would. That could be an exciting experiment.

I put one together using a modern automotive (waste spark) coil, just a short wire fence to keep deer off the flower beds.
Just Mosfet switching the input side.

 

What was the primary voltage that you used? I was going to try using a mains powered fence charger circuit board, so the pulse will probably be about 150 volts to the coil primary, instead of 12 or less.

 

120v AC transformed down and rectified. to 12vdc
I used a small micro to supply a pulse to the primary every second.