problems with wire feed when using Kende 150

[rob passfield]

Hi all, I need some thoughts on a wire feed problem I am having with my Kende 150. Problems started recently welding new spring boxes into my MG Midget. When using the handset without any twists or bends the welder works ok, but with a little more splatter than before. But when any slight bend or twist in the hose, wire continuously burns back to the tip of the contact tip. I have renewed the liner, changed the contact tips, checked connections at the mains plug & internal cables. I have observed the wire feed without making an arc & all looks smooth & without snagging, but as soon as the arc is struck the burn back is apparent. I have tried another spool of 0.6 wire, no change. Someone has suggested a new grooved roller in the wire feed? What do you think? Any help would be welcome. The wire feed is similar to the sealey mightymig 150.

 

[mike 109444]

IF your wire feed unit has any plastic parts to it like some of the Clarke + SIP + (Sealey?) then examine it closely to see if there are any crack where it might under load (slight bend in torch lead) open up and stop the pressure rollers from griping the wire fully AND squarely.I would think it would be difficult to see when watching the rollers when feeding to see any skipping of feed. Also try cleaning out the groove (bit of wet and dry but don't polish or it will slip even more!) Take a look at the various mods don to the feed system on the SIP's and Clarek's
And welcome BTW

 

[rob passfield]

Thanks for your reply. I have looked at the wire feed unit but can't see any thing amiss.I cleaned out the groove yesterday using a small screwdriver & paper towel.I am considering two options now, renewing the roller or trying .8 wire & use the old roller, other than that its a replacement machine!

 

[Wendelspanswick]

My Tec-Arc MIG came with a roller stamped 0.6 and 0.8 but it must have been mis-marked as it is actually 0.8 and 1.0.
It did throw me to start with as I set the larger groove on the roller to drive the 0.8 wire that I was using and it kept slipping, it was only on closer inspection that I realised I needed to use the smaller groove and ignore the markings.

 

[Robotstar5]

It should take quite a hard pinch of finger and thumb to stop the wire feeding, if the rollers slip easily there is not enough pressure. Could be due to worn rollers or on a lot of hobby welders the plastic frame can flex/bend stopping the rollers applying enough pressure. Try running an offcut length of wire through, will prove the reel is not the problem.

 

[rob passfield]

Thanks for your input. I went to see a professional welder today, he almost instantly diagnosed the problem... the speed control for the wire feed is not working
It is feeding the wire at full speed, no matter what the control knob is set to.. (I feel quite bad that I missed something so obvious)!. the power transistor is a tip35c.
I have removed & tested it, but it seems to test ok, I am having problems finding a circuit diagram on the web for this PCB. Anyone know where I can find a diagram?
I am off to Rapid Electronics tomorrow in Colchester, hoping they will have replacement components.

 

[mike 109444]

You might find that a resistor that provides the bias (control) for the transistor has gone open or short turning the transistor full on. You should be able to find most components for the board and if you follow the tracks that lead to the transistor you should be able to find the duff item.
Can you post pic of pcb ?

 

[rob passfield]

Photos are the same as thread: http://www.mig-welding.co.uk/forum/threads/kende-no-wire-feed.39836/ I am hoping its the adjustable pot which I have bought today, & I have ordered a replacement tip35c from rs, I have been looking at an independent voltage regulator, I saw a YouTube film where someone had fitted a Tyco train controller which gives a smoothed feed to the motor, but can't see where to get hold of one.

 

[rob passfield]

Bit more progress tonight, changed the pot, still shows full voltage feeding to the motor, so I pulled the base leg off the tip35c, still showing full voltage feeding the motor, sh1t or bust, I pulled the whole transistor off the board, & still full voltage going to the motor..???? Will need to have a look at the PCB a bit closer, but it is difficult with no diagram to work to..

 

[mike 109444]

Is the motor connected to pins 6 & 7 ? (red and blue) ?

 

[mike 109444]

Note it is a double sided pcb!

 

[rob passfield]

Yes, the wires are all black on mine, but the motor feed is pins 6 & 7. I need to work out how the 20v is arriving at 6 & 7. I am measuring the voltage with no load connected, do you think that could give me false readings? I could try reconnecting the motor & check again.

 

[mike 109444]

Yes, the wires are all black on mine, but the motor feed is pins 6 & 7. I need to work out how the 20v is arriving at 6 & 7. I am measuring the voltage with no load connected, do you think that could give me false readings? I could try reconnecting the motor & check again.

Ref the 20V I would say yes, with no load the voltage would rise unless there was a pull down resistor.
As the transistor SHOULD control the voltage feed to the motor and as removing from the circuit still allows the full voltage then there must be something between the transistor and the motor wires at the plug (pins 6 and 7) that is pulling the voltage up ? Most of the components concerned with the motor control are on the right side of the pcb (when looking at the UNDERSIDE, top pic of the two) Have add the transistor pin ID's to the pic

 

[Keith Tween]

IF your wire feed unit has any plastic parts to it like some of the Clarke + SIP + (Sealey?) then examine it closely to see if there are any crack where it might under load (slight bend in torch lead) open up and stop the pressure rollers from griping the wire fully AND squarely.I would think it would be difficult to see when watching the rollers when feeding to see any skipping of feed. Also try cleaning out the groove (bit of wet and dry but don't polish or it will slip even more!) Take a look at the various mods don to the feed system on the SIP's and Clarek's
And welcome BTW

Hello Mike, You seem to have a good handle on these probems. I have a Kende MAG-150R that needs attention. Do you know anyone near Doncaster who could assist?

 

[mike 109444]

Unfortunately I don't know of any one in the Doncaster area that would assist.
Best bet would be to post on this post the issues you are having and the collective will try to assist.