TORO 5000 electric fence transformer repair (help needed) - Page 1
Forum section: electronics / repair

author: Bilpe
author_rank: Newbie
timestamp: August 05, 2017, 11:53:09 am
content: Greetings!A little background; A friend gave me a non-functional electric fence transformer, hoping i could take a look at it. The fault might have occurred during a recent lightning storm, but it could just have given up on its own (it was made in Sweden during the early 90's.). The symptoms of the fault are simply not turning on. there is a neon indicator attached over its capacitors that doesn't turn on.I'm a real novice on electronics repair, and hoping someone could recommend what steps to do next.There was a thermal fuse attached to a large resistor that had triggered, but bridging it does not seem to restore function.I took a picture with my phones thermal camera, showing that there is a TO-220 package that gets hot (apart from the resistor with the fuse).I think its a thyristor, marked S2014NH(http://www.semicon-data.com/scr/thy/s0/S2014NH.html) & TAG8534 (The 16-pin package close to it is marked HEF4060B).My plan would be to change the overheating thyristor, but i cant seem to find that model anywhere (perhaps i'm not looking at the right place?).The transformer itself seems to be in good shape (i'm getting continuity between input-input & output-output, but no connection between inputs-outputs)Any help on how to proceed would be greatly appreciated!Best regards, Billy

author: Armadillo
author_rank: Super Contributor
timestamp: August 05, 2017, 02:35:38 pm
content: Is the IC 4060 oscillating?1.0 Measure Pin 16 and Pin 8, What is the DC voltage?2.0 Use a logic probe, is Pin 7 any pulses?3.0 Check if thyristor is short-circuited between Anode and Cathode.?

author: Bilpe
author_rank: Newbie
timestamp: August 05, 2017, 04:22:04 pm
content: Thanks for your answer!1. The voltage between pin 16 and pin 8 is 4.5v (it moves between 4.3 and 4.8v).2. Unfortunately don't have a logic probe (yet). But measuring with my cheap multimeter, i'm getting rise and fall between roughly 0v and 4.8v (rising and falling in about 6s, then repeating).3. Using the continuity mode on my meter, i'm not getting continuity between Anode and Cathode (in either direction). I'm getting continuity between Cathode and Gate (in both directions) thou, i don't know if that's how its supposed to behave.

author: Armadillo
author_rank: Super Contributor
timestamp: August 05, 2017, 04:46:04 pm
content: Quote from: Bilpe on August 05, 2017, 04:22:04 pmThe frequency is way too low for switching. Check the component values at pin 9 and pin 10 and use the formula as attached to verify the frequency. I can't see from the photo the connection.The transistor apparently is used to buffer the clock to the gate of the thyristor. Also prode at the gate to see if there are pulses firing it.Digital logic probe can be very useful here. It is also not expensive [ < $10?]. Recommend you keep one.If the transistor is shorted, the gate is always fired, [showed on your thermal as hot]. Also if the frequency is too low, it will be hot as well and no output generation.

author: Armadillo
author_rank: Super Contributor
timestamp: August 06, 2017, 01:12:36 am
content: On a second thought, the HEF4060 may be counting at the line frequency as depicted in the attached, so maybe pin 9 and pin 10 are left unconnected in the circuit board.?If this is the case, the slow pulse you measure may be correct after all.I think logically is to probe the gate of the thyristor whether it received the clock otherwise suspect the transistor.If the gate didn't receive any clock, your thermal should not be showing it as hot hence I would change the thyristor as defective.The S8016RTP or 2N6405G may be compatible replacement.