sip pcb

[baggy]

the diode on my sip autoplus 150 has exploded,cosequently i can`t read the id number on it.local electronic shop need to know the voltage etc. any help please...

 

[R Kraft]

Which diode, can you take a photo ?
Robert

 

[baggy]

can`t do foto.will draw

 

[R Kraft]

Does this photo help ?:http://www.mig-welding.co.uk/forum/showpost.php?p=158633&postcount=7
The diode in this photo is the black thing with the silver or white band on one end.
Is that what blew up ?
Robert

 

[BChild]

I don't know where I picked up this picture but I know why I saved it - ignore the ringed item - I hope this helps

 

[R Kraft]

A 3 amp at 100 volts or more should be a plenty big diode.
Robert

 

[baggy]

thanx for that,have ordered 3a 100v diode.wonder if you help with how i managed to blow up the diode (and a transistor) in the first place...i needed to cut off and replace the axle for the rear wheels.i earthed the case of the machine with the earth clamp and did the job.next time i used the mig the motor ran backwards.took the side off and swapped the motor leads round and did a weld on a bit of scrap steel,welded almost ok, `almost `coz although the wire speed adjusted fine the weld seemed too hot burning holes.then the transistor and diode exploded???

 

[R Kraft]

Sounds like an output diode went short , at a guess.
Robert

 

[baggy]

thanx for reply.am going to replace 3 amp diode and tip35c transistor as both are completely destroyed.parts should arrive tomorrow will post result

 

[R Kraft]

If the output diodes went out, it will probably burn the transistor and the diode out again.
Use a meter and make sure it is putting out DC to the torch tip when the torch button is pressed.
Robert

 

[baggy]

parts not arrived yet.what type of `meter` would indicate dc?

 

[R Kraft]

You just a VOM/Volt Ohm Meter.
Even a simple one like this would work.:http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=90899
Robert

 

[baggy]

just fitted components to circuit board.motor still runs backwards.dc at tip

 

[BChild]

just fitted components to circuit board.motor still runs backwards.dc at tip

Swapped the leads back?

next time i used the mig the motor ran backwards.took the side off and swapped the motor leads round and did a weld on a bit of scrap steel,welded almost ok, `almost `coz although the wire speed adjusted fine the weld seemed too hot burning holes.