Hi Folks

I’m looking for some specialist help here. For the last few weeks I’ve been attempting to reverse engineer a circuit board to create a schematic diagram using “Circuit Wizard” and photographs. There could be mistakes in my interpretation from board to schematic, but believe me I’ve checked and rechecked until my brain hurts.

The board “was” the brains of an electronic fencer used to control cattle etc, with a pulse of energy of around 10000 volts. It ceased working and was handed to me by the local farmer to see if I could do anything with it. On first inspection I noticed a 220uF electrolytic capacitor (C2 circled green) that had exploded and deposited its feathery contents all over the board like webbing, but replacing it didn’t solve the problem. It either took something else with it or something vice-versa.

Looking at the fenceboard.jpg image and circled in red was a component marked as Q1 (Transistor??) but is an unknown. I removed it from the board for identification because it looked either badly burned or caked in lacquer, but either way I couldn’t find any markings to identify it. The only notable difference I can see is on the board’s component placement which depicts a more elongated shape rather than that of any other transistor placement marking on the board, circled blue. In it’s place on the schematic it's now labeled as Q6, a NPN circled red, but really I have no idea what was there.

Please note the component labelled 2N6028 circled yellow, I do not have any Programmable UniJunction Transistors in the “CW” program database so I’ve inserted a Thyristor symbol instead just as a representation. It’s marked D2. Switch (SW1) I think is to increase/decrease the output power to the HT coil if needed and I’m assuming the 2N6028 is the timing device to trigger D4, C106C but after that I’m a little stuck.

I’d be really grateful therefore if someone out there could help me understand how this circuit should work and where the primary coil on the High Tension transformer gets it supply. Also any info as to what the D6 component should be?

Many thanks in advance

Links to:
Photo: http://www.jacarandatree.co.uk/fenceboard.jpg
Circuit: http://www.jacarandatree.co.uk/fenceschematic.jpghttp://www.jacarandatree.co.uk/fencecircuit.cwz
Should anyone use Circuit Wizard here is the file: http://www.jacarandatree.co.uk/fencecircuit.cwz

 

I would say Q6 and T2 form a charge pump oscillator charging up C4 to a high voltage, assuming you have drawn the circuit correctly, then the thyristor D4 shorts C4 across the transformer T1 to produce the spark.

It's the same principle as an electronic ignition system on a car.

 

2N6028
Mouser
$2
https://www.mouser.com/_/?Keyword=2N6028
D6: same as D5. 4.7 volt zener

 

Thanks for the replies.

#12: I'm sorry I meant to ask what the component Q6 should be, not D6 as I already now this.

Cannot seem to find a way to edit the original post?

 

Thanks for the replies.

#12: I'm sorry I meant to ask what the component Q6 should be, not D6 as I already now this.

Cannot seem to find a way to edit the original post?

To Edit,, Click on the 3 horizontal lines at the bottom of your post.

As for Q6 show a picture of the original transistor.

 

To Edit,, Click on the 3 horizontal lines at the bottom of your post.

As for Q6 show a picture of the original transistor.

Hi

I don't see any horizontal lines anywhere on my posts in order to edit..

As I tried to explain in my OP:-
On the fenceboard.jpg image and circled in red is where Q1 was located and it looked like any other standard transistor on the board. But because it appeared either badly burned or caked in lacquer I removed it from the board for identification but couldn’t find any markings at all. So I then thought that somebody might be able to recognize its PCB placement symbol to identify its type. It depicts a flatter and more elongated shape rather than that of any other transistor placement symbol on the board, examples of which are circled blue.

On my schematic, the original PCB Q1 has now been labeled Q6 and circled red, but it's only been added as a representation of the original Q1 whatever it was. Unfortunately I don't have a picture and that's why I'm asking the community for any ideas.

Thanks

PS. After posting this message I can see a pencil and an EDIT link but this has disappeared on next visit to the forum.

 

PS. After posting this message I can see a pencil and an EDIT link but this has disappeared on next visit to the forum.

Which version of the forum are you using? There are two, one known as the "orange" one and the other the "blue". And are you logging in each time? Without a login you can read but not make changes.

 

Which version of the forum are you using? There are two, one known as the "orange" one and the other the "blue". And are you logging in each time? Without a login you can read but not make changes.

Hi Shortbus

I browse to: www.allaboutcircuits.com, login and click on forum. The menu bar is orange and I'm not aware of anything blue. I do login each time when I need to post etc. As I mentioned in my previous post, I am now able to and just have edited this thread but when I re-login there is no option to edit. Maybe it's because I'm a new member? Please respond if there is something I'm missing here?

Cheers

 

I'm on an Android phone using Chrome browser and the little hamburger menu at the bottom that holds the edit only works when the phone is rotated sideways. When it's vertical there is not enough room on the screen and the menu isn't shown at all. Samsung S7

 

I'm on an Android phone using Chrome browser and the little hamburger menu at the bottom that holds the edit only works when the phone is rotated sideways. When it's vertical there is not enough room on the screen and the menu isn't shown at all. Samsung S7

I'm using my Macbook so the screen is isn't the issue, but thanks

 

I'm on an Android phone using Chrome browser and the little hamburger menu at the bottom that holds the edit only works when the phone is rotated sideways. When it's vertical there is not enough room on the screen and the menu isn't shown at all. Samsung S7

Yes i know, it does this with me too on my phone, Very Annoying!!

Clearly somebody hasn't done their job properly!

 

Hooray, for whatever the reason, "Edit, Delete & Report" has suddenly appeared at the foot of each of my posts. Thanks whoever!