I have been having some problems with diodes on my nbc 140. While I was in the shed playing with my meter I thought I would check the diodes on my cebora mig 180. I checked the three diodes on the top left of the board and the bottom one is shorted. Can anyone tell me what those diodes do? The welder can be a bit hit or miss and I am wondering if the shorted diode might have something to do with it.
- Thread starter jay1800si
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weaverwelder
New Member
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rtbcomp is correct it is very hard to get good reading on diodes or caps resisters transisters hooked to board to many parts feedback on readings/values ,,its very hard to test that way without factory specs/values at every point to be tested on that board ..
NotANormalCoder
Retired fixer of welders
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Don't get too hung up over a shorted reading across one of these diodes. I don't have one of these PCBs to check but usually Cebora use these heavy diodes to provide the DC for the motor and also one across the motor output as mentioned above. Often, the motor is also shorted by either a relay or heavy transistor, when the trigger is released, to provide 'braking' to stop it quickly. It could easily be that what you are measuring as a short is in fact normal.
You don't elaborate on the problems you are having but if the motor starts, stops and varies correctly when not under load without blowing any fuses, then it is very unlikely that you have a pcb problem. Experience tells me that when a mig is a bit troublesome, you should always check and service the torch (tips, liner, nozzle etc) and the earth lead/clamp. Then, if this doesn't give a vast improvement, clean out the machine and then check/tighten all the connections inside.
Hope this helps. Dave
You don't elaborate on the problems you are having but if the motor starts, stops and varies correctly when not under load without blowing any fuses, then it is very unlikely that you have a pcb problem. Experience tells me that when a mig is a bit troublesome, you should always check and service the torch (tips, liner, nozzle etc) and the earth lead/clamp. Then, if this doesn't give a vast improvement, clean out the machine and then check/tighten all the connections inside.
Hope this helps. Dave
Thanks for that dave. The motor on the welder works fine. The torch was replaced when I got the machine and has done very little.. The earth lead is new but the clamp looks a bit iffy. Does the earth clamp make a big difference? I cant really describe the problem I just find it hard to get a smooth weld with it. Maybe its operator error!
mike 109444
Member
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Simple answer YES. It completes the circuit from tourch tip to mig wire to metal you are welding into earth clamp and back to machine.
If you are into cars try loosing the earth clamp on you r car battery then try starting = iffy starting sometimes !!!
NotANormalCoder
Retired fixer of welders
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- Surbiton - Surrey -UK
Earth lead - As Mike stated above. Quick check is to run a 2" bead, then stop and run your hand over all the earth lead connections. Anywhere you can feel heat is a poor connection and they get worse over time. Clean and remake is good.
Also, I suspect your machine is the model 850 (hard to be sure from your pix). These machines were odd in that they would only run nicely between voltage settings 1 to 3 using 0.6mm wire. 0.8mm only really worked well on settings 3 and above.
Check your gas flow. Assuming that you're using an Argon/Co2 mix, you only need a gentle flow to keep the atmosphere away from the job. Too little and you'll get porosity, too much and it tries to blow the arc out.
Interesting anecdote: I once had a guy arrive saying his new mig welder "wouldn't fire up". Asked him to demonstrate the problem - He pulled the trigger, then produced a lighter from his pocket and attempted to light the gas coming from the end of the torch. "See" he said, "it doesn't work". I had to have a serious talk to him!
Dave
Also, I suspect your machine is the model 850 (hard to be sure from your pix). These machines were odd in that they would only run nicely between voltage settings 1 to 3 using 0.6mm wire. 0.8mm only really worked well on settings 3 and above.
Check your gas flow. Assuming that you're using an Argon/Co2 mix, you only need a gentle flow to keep the atmosphere away from the job. Too little and you'll get porosity, too much and it tries to blow the arc out.
Interesting anecdote: I once had a guy arrive saying his new mig welder "wouldn't fire up". Asked him to demonstrate the problem - He pulled the trigger, then produced a lighter from his pocket and attempted to light the gas coming from the end of the torch. "See" he said, "it doesn't work". I had to have a serious talk to him!
Dave
I have never thought about it like that mike I get what you mean about the car earth lead I suppose the lead on the welder has a lot of current to deal with too. Dave the welder is an 852 model. I am using 0.8 wire usually on setting 2 as I am mostly using it for car bodywork. Now that I think about it the machine does weld better on the higher power settings. I am using argon/co2 mix and I think the flow is ok. I will get a new earth clamp and some 0.6 wire and see how it goes. Thanks for the advice I never would have thought of changing the wire size. I bet the guy trying to light the mig felt pretty stupid!
octo0072000
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the sizzle
have a look here to get the sizzle for the wire speed
http://www.youtube.com/watch?v=f4RbBudvHLU
have a look here to get the sizzle for the wire speed
http://www.youtube.com/watch?v=f4RbBudvHLU
