Electronics > Repair
Electric fence energizer repair
(1/3) > >>
Bubaaak:
Hello,
 I am trying to repair energizer for an electric fence. The model is Horizont ranger an50, no schematic available. As it's mcu controlled it should be switched on by a press of a button, but it's completely dead. No signs of water damage, however as used outside it's possible.
The picture of the board is in attachment. I have tried to measure some of the components and haven't found anything wrong so far. It's taking about 20mA at 12V, with the power button pressed it goes up very slightly (by about 0,5mA).
I have identified  buck converter for mcu at the top left corner, with both input and output caps having the correct voltages (3,37v at the output). The power switch is connected to the "SW" terminals near this circuit, where one being ground and the second one going to pin 46 of the mcu, as well as the "Wake" terminal near the mcu itself. (3.3V at this pin as well )
Although I already doubt it is repairable, I would appreciate any suggestions on what to check /try :)
fzabkar:
In the middle of the bottom edge of the PCB is a transformer, a diode and a large capacitor. Do you measure any voltage on this capacitor? I presume that the SW terminals will need to be shorted to switch on the unit.

Warning: This area is a high voltage supply.
Bubaaak:
No, there is no voltage on that capacitor, with or without SW terminals shorted. I assume(d) this boost converter for the actual fence voltage supply is controlled by the mcu and it's switched on only when the whole thing is turned on. But your post gave me idea it might be an issue with this boost converter and the unit doesn't want to turn on because the mcu doesn't see any voltage on it's output, so I will try to focus on that area.
fzabkar:
The SOT23-5 IC appears to be the PWM controller for that boost supply. Can you identify its markings? Perhaps its Enable pin is inactive?
Bubaaak:
Had to scrape the coating, it's marked FFUR. Pins 3&4 are common and connected to Gate of near mosfet, 2 is gnd, 5 is +12v and pin 1 goes all the way to the little board behind the grey capacitor, which on both sides contains HC4538 multivibrator, divider to sense the high voltage, comparator and one/two and gates.  Pin 1 goes specifically to the output of both comparators.

Edit :looks like I got the pins mixed up, hopefully it's correct now.
Navigation
Message Index
Next page
There was an error while thanking
Thanking...

Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod