Electric fence with an unknnown component - Page 1
Forum section: electronics / repair

author: gg64
author_rank: Regular Contributor
timestamp: September 21, 2018, 11:57:29 am
content: Hi there.I am very new on the eeblog forum.So I got an electric fence (for cattle) that I am trying to repair.The advertised specs are: 3Joules, 10kV.Though I did not checked it, it was able to make quite a spark.So it started to be really about weeks ago, it would not even show any signof voltage onto the purposely designed voltmeter (basicaly I think this is just a bunch oflamp with different resistance on them: I will call the ACME tester).So after some test with it, I concluded it was the pulse coil that was deffective.So I order a transformator (pulse transformator) core from ebay, received it.I coiled it as at least like the former one (ratio of 10/1).I tested with 10/1 nothing (onto the ACME tester) but it was able to make a small spark.So I decided to go for 20/1, then I can see the lamps flashing onto the ACME tester.After discussion with the user, we decided to ramp up to 30/1. Still working onto the ACME tester.So I put some tips on the transformer (to make final installation).I connected again the transformer with the load but I thought I plug correctly the transformer's primary (I DID NOT...)I heard a tick sound.So after some trouble shooting I concluded that the bt139-600 should be fried.I bought 5 from ebay (along with some diodes (20x) em516 and a condensator 400vac 1µF).1st try: Installed one the board, fried (not when connecting with the old tranformer the new one, with 30/1 ratio)2nd try: Installed one the board, fried (not when connecting with the old tranformer the new one, with 10/1 ratio)3nd try: Installed one the board, fried (not when connecting with the old tranformer the new one, with 1/1 ratio)I measured 18kohm onto the old transformer, and the capacitor (in serial with the pulse tranformer) was reaching about 420v.I decided that's enough. I should seek help. I am missing something.Please note, according to the writing the fence should not go quicker than about 1Hz (he does: about 901ms period)Here the schematics I reversed engineering except one components I can't figure what his specs are, is this a diode ?(I got an idea but I don't want to skew people's opinion)The "diode?" got a blue stripe right in the middle, I would like to know the value is supposed to be.Here as join piece a QUCS schematic with the component named "whoami".A photo with the unknown "diode?" circled in red (my cameras on my smartphone are dead, so no real nice close up photo yet, this is taken from a webcam)Btw the simulation is not working for some reason (on QUCS) but it is basicaly a power side (left on the photo) and a pulse control side (right)Also, I don't have osciloscope (i wish I had one....), no attenuation device, just multimeters able to go 600v and a capacitor meter.QUESTION:Does anyone can identify the compenent named "whoami" on the schematics (red circle on the photo) ?I would be really thankful.

author: gg64
author_rank: Regular Contributor
timestamp: September 21, 2018, 12:01:53 pm
content: I didn't understand how to put several attachements as a first post, sorry. (missed the more attachments button)Here are the rest.

author: capt bullshot
author_rank: Super Contributor
timestamp: September 21, 2018, 12:04:03 pm
content: Can't find a schematic within you post ...As a wild guess from the photo and your description saying the circuit uses a Triac (the BT139), it might be a DIAC (triggering device). Especially if one end is connected to the Triac Gate.

author: gg64
author_rank: Regular Contributor
timestamp: September 21, 2018, 12:12:35 pm
content: I forgot an attachements sorry, check the schematic as a second post.I am trying to revive up an old smartphone, to take a clear close up photo.

author: tpowell1830
author_rank: Frequent Contributor
timestamp: September 21, 2018, 12:14:06 pm
content: I would say it is a zener diode from the awful, out of focus, low light photo. No way to tell what value zener.

author: gg64
author_rank: Regular Contributor
timestamp: September 21, 2018, 12:47:14 pm
content: Here are some close up photos of the board.https://imgur.com/a/H1LAujC

author: MK14
author_rank: Super Contributor
timestamp: September 21, 2018, 01:16:43 pm
content: Here is one picture of a Diac. Someone else mentioned Diac in this thread as well.Diacs often go with Triacs, as they make nice triggering devices.

author: gg64
author_rank: Regular Contributor
timestamp: September 21, 2018, 01:25:27 pm
content: Oh, I never seen those. Thanks you, it seems to check out.I know this is an english speaking forum but according to this website (in french, yes I am French deal with it):https://www.astuces-pratiques.fr/electronique/le-diac-composant-electroniqueIt is common to use diac with a triac.Here the same kind of information in english:https://www.electronics-tutorials.ws/power/diac.htmlSo that will point me to check the power resistors I guess ? (not sure about it just yet....)