Kende no wire feed

[PaulC7]

Got a Kende 105/f for nothing as it has a wire feed problem even though its not been used much.

Turns on an fan kicks in and when pulling trigger a clicking from a small black box can be heard.

Had a good look inside, all wires are fine, all connections are good, but noticed the wire feed motor wasnt running... so connected 12v battery to motor and all worked fine but a componant glew red and started smoking heavily.

Took off the part which i was told is a resistor... RX1-10 0.5 +5% an bought a 10w w/w 0.56r

After fitting and putting everything back together the problem isnt solved.

Im not an electrical person by any means so any help sorting out the problem would be great thanks.

 

[PaulC7]

Anyone got an easy to understand way of testing a pcb for a faulty part?

 

[mike 109444]

When you put 12v to the motor was it still connected to the wiring of the machine or did you pull the connectors off?
If you post a pic of pcb both sides if poss and an indication of the resistor that fried.

 

[PaulC7]

Yes it was still connected... only aplied power to the motor for a few seconds.

Green and brown resistor that was the problem.

And with new one fitted although obviously bigger... dont know what effect this may have.

 

[mike 109444]

Not a good ideal to connect the power to the motor with it still connected to the machine as you are now putting 12v into the circuit that is suposed to be outputting the voltage to the motor! The new resistor even though it is bigger will be ok solong as it is the same value of resistance and equal wattage or greater. It will prob get hot in normal use so watch your fingers. Will try and get time tomorrow to figure circuit out and make some sugestions for metering. There does look to be a blob of solder going across three of the tracks just below the white plug pins ?

 

[PaulC7]

Beginners mistake i suppose.

I see what you mean about the blob of sloder... that is not my doing, on the component side between the new resistor and terminals to motor there are 3 silver squares so i guess they should be there but the solder should not be across the cicuit as it is.

I have a basic kind of MULTIMETER... mostly used for testing power feeds and continuity on vehicles... this will be my first PCB ive tested.

Thanks for taking the time.

 

[shenion]

That blob looks like 3 pads ro be used as a jumper for different configurations.

 

[PaulC7]

Would a jumper be done by the manufacter or hobby welder... and what would be the point in altering a welder... surely if you needed it for bigger/better things you would buy what would suit your needs.

 

[shenion]

That jumper looks like it is there so the same board can be used in different models.

 

[mike 109444]

Ref your wire feed problem. WITH THE POWER OFF! I would lok to take the lid off the large relay in the bottom right of you pic and clean the contacts (fine emmery board to clean) Then look to replace the smaller relay (small black box top middle of pcb) should only be a few bob. What numbers are on the transistor device mounted to the heat sink?
Are you still getting the click when pressing trigger?
This is what I have orked out so far. Bit difficult when you can't see all the components from the side and there markings also not knowing where the wires go.

 

[PaulC7]

Transistor doesnt have any numbers on it... only the BCE markings on the board.

NO longer get the clicking when pulling trigger.

Tell me what numbers of what bits and i will let you know.

 

[NotANormalCoder]

The PCBs and wiring on these machines is notoriously bad. I've even had one for repair that was wrongly wired at the factory - not a good advert. As the main welding supply also feeds the PCB with voltage to the motor, if you get the trigger to work, check for 20-50V DC across the earth lead and contact tip. No voltage will give you no motor and indicates a fault either with the wiring or the big black relay on the board.
If you replace the relay, make sure that it is *exactly* the same type, as some relays on these machines are not normal. Can't remember which one but at least one relay is a special 'latching' type. It doesn't work just by feeding it a voltage, it needs DC to energise, then reverse polarity to de-energise. Goodness knows who thought that this was a good idea.
Dave

 

[PaulC7]

Well got my new relay... and the first thing i spotted was it has 5 prongs where as the old has 4 but evidently had 5.

So a broken resistor and relay i am hoping are all that is wrong.

Going to start putting it together now... watch this space.

 

[PaulC7]

New relay fitted and now get a continuity reading from it to the 2 terminal connections that then go to the motor.

Fingers crossed now

 

[PaulC7]

Still no joy []

Got the clicking back when i pull trigger.

As for checking for DC... which earth point?

I used an earth point on the body of welder and got 24V.

There is continuity from the clamp to the tip so no breaks along the way...

guessing just no power getting to the tip and motor... could it be the transistor is dead... from what ive read this is needed in all PCBs and if not working then other stuff wont work properly.

 

[shenion]

Checking which DC?

Output would be between the torch and return lead.

I'd check D1 to see if it is open. The wire feed circuit is not complicated, the only other part that would likely fail is the transistor.

 

[PaulC7]

checking for 20-50V DC across the earth lead and contact tip

 

[mike 109444]

Just notice this is a double sided (tracks) pcb!! That would explain why some of the components looked unconnected eg the fuse!
If you were getting 24v when you do as Shenion has sudgested then the welding current is ok. Note this value should change as you change the power setting on the welder.
You migh find with a good light and magnifiing glass there is a part number on the transistor. Sometimes they are etched on rarther than printed. Write down any numbers youfind on it.

 

[PaulC7]

With a 78 LED torch and a modeling magnifying glass the numbers are...

TIP35C
CCD8B
MAR 839

 

[mike 109444]

The key number there is the "TIP35C"
http://www.ebay.co.uk/itm/TIP35C-NP...al_Components_Supplies_ET&hash=item2a27aa526d