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Plasma Cutter with pictures

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b.james

Member
I have one of these cheapies named Bellcarroll Cut 40 . It has an automatic start mechanism which has failed and I wondered if anyone knew where I might start looking . Its got a few boards on it
When cold and first switched on a small starter spark appears when touched to ground for half a second and then nothing thereafter.

I'd like to save it because it does a mighty job when working.
I Include as many snaps as I can get up

Plasma4.png

Plasma2.png

Plasma3.png

Plasma 1.png
 
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spec

Well-Known Member
Most Helpful Member
Hy b.james,

Where are you: care to put it next to 'Location' on your user page so that it shows in the window on the left of your posts.

Wow, that is quite a machine: great pictures too. I am amazed how clean your plasma cutter is inside.

Without a schematic, and knowing a bit more about the symptoms, it would be difficult to diagnose the fault but here are a few words:

With any system it is always a temptation to blame the most complex and expensive part for a fault, but often this is a misnomer. In this case the obvious contenders are the controller board and the row of Insulated Gate Bipolar Transistors (IGBTs), assuming that's what they are.

But often it is simple things that cause a fault, like a loose connection, a corroded connector pin or solder joint or broken wire or cracked Printed Circuit Board (PCB).

Although your plasma cutter is probably well designed from the electronic point of view, some of the mechanics look a bit suspect, especially the mounting of the toridal inductors. It is a common fault for the mounting glue to fail and the self leads to fracture. Or the toroids can move and short to other components. In general in this type of construction components shorting to other components is always a danger.

So what I would advise is to methodically and thoroughly inspect the machine from nose to tail for physical problems first.:)

spec
 
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tcmtech

Banned
Most Helpful Member
Sounds like the ignitor circuit is working but the main power supply is not starting up.

I would start out by checking to see if the main DC power rail for the inverter circuit has proper, if any DC voltage, when it's trying to start.

If it does then the problem is either in the drive circuitry or control circuitry.
 

Tony Stewart

Well-Known Member
Most Helpful Member
With only EBay sourcing of these cheap units, repair will be difficult unless you can locate the factory in China by email.

You will have to rely on your debug skills to isolate the fault in the low <100V voltage 30A SMPS using a scope and tracing input power to the regulator.

It appears to have many of the necessary ferrite beads and magnetic coils to operate in this extreme harsh EMI environment.


Was there a surge event that caused this failure on the input or output or a heavy duty thermal rise.

Good ruck.

It might be quicker to buy a 2nd unit and use it to compare voltages then sell the used unit after repaired.
 

b.james

Member
Sounds like the ignitor circuit is working but the main power supply is not starting up.

I would start out by checking to see if the main DC power rail for the inverter circuit has proper, if any DC voltage, when it's trying to start.

If it does then the problem is either in the drive circuitry or control circuitry.
It would seem to be the ignitor circuit that is not working . What would I look for to identify where the ignitor circuit is please
 

tcmtech

Banned
Most Helpful Member
It would seem to be the ignitor circuit that is not working . What would I look for to identify where the ignitor circuit is please
Okay which is it?

When cold and first switched on a small starter spark appears when touched to ground for half a second and then nothing thereafter.
If you have the pilot arc then the starting circuit is obviously working but it timing out because the main power for the high current cutting arc is not being produced.
 

b.james

Member
Not understanding what goes on I express it as I see it .As I said when cold I pull the trigger and a small sparking takes place for just a second . Nothing starts , I let go the trigger and try again . This time and every other time thereafter no sparking whatever .
Does this fit the situation that you envision? Perhaps it would help if you would explain the sequence of events that get the plasma arc started and maybe describe what the board might look like for the "pilot" and the "main power" parts of the circuit.

If you are kind enough to take the time to respond why do you use such short sharp language .If you intend me to get some assistance out of your post then perhaps an explanation of how they work would be a good starting point . Perhaps then I could start to understand its working and then be able to help myself fix it.

An arrogant " whats this about then?" approach is not going to help anybody . Perhaps I should attempt to kiss your arse so that I may get a better response from you . Would you like that perhaps?
Thank You
 
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tcmtech

Banned
Most Helpful Member
If you are kind enough to take the time to respond why do you use such short sharp language

I'm covered in poison ivy rash from my wrists to my elbows from cleaning out and repairing a round baler that had a fire earlier this week. That's why. :(
That and I am apprenticing to be cranky old fart someday plus I did ask you what your main power supply voltages were doing to which you never gave me a reply so I assumed you either can't read or have no electronics skills whatsoever or both (Which lately there has been way too many posts like that on the forums and it gets to me too.) :(

Kissing my butt just makes things worse with me. :oops:

anyway, :nailbiting:

When you first press the trigger the logic control board will activate the starting arc circuit that produces a low current high voltage high frequency signal that is superimposed on the main high current lower voltage output of the main power supply that does the actual cutting. Being you are getting the small light arc for a second or so that suggests that the pilot arc striking function is being properly generated but the main power supply is not activating to establish the primary cutting arc so the control board see that and shuts things down most likely going into a fault condition mode which is why it wont do it again until the whole system has been powered down and reset.

Without knowing where your incoming AC power is going and ultimately stopping at, it should be showing up as the higher voltage 350 - 380 VDC on the main power supply capacitors, and if not where is it ending at I can't speculate on anything further. ;)

Better? :troll:
 

spec

Well-Known Member
Most Helpful Member
How a plasma cutter torch works:


 
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b.james

Member
All very good information . Thank you very much Spec.
The one titled Chinese is rubbish , you might remove that
The one titled Troubleshooting Lotus is brilliant and will definitely help me
The one titled How it works (teardown) is pretty well twice the size and pretty laborious to listen to but I may get something from it if the other does not find it
I took them in order of size as I am on a boat and download challenged.
I'll get the longer ones if this one above does not fix it
Thanks again
 
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spec

Well-Known Member
Most Helpful Member
All very good information . Thank you very much Spec.
The one titled Chinese is rubbish , you might remove that
The one titled Troubleshooting Lotus is brilliant and will definitely help me
The one titled How it works (teardown) is pretty well twice the size and pretty laborious to listen to but I may get something from it if the other does not find it
I took them in order of size as I am on a boat and download challenged.
I'll get the longer ones if this one above does not fix it
Thanks again
No problem b.james,

You still haven't told us where you are from.

All of the videos should be of some help. I would just ignore any references to Chinese rubbish.:)

spec
 

b.james

Member
Actually the guy who is doing the chinese one is a fool and I suggest you watch it cause its not the way to do about fixing anything nor instructing anyone .
These little blue things ,I don't know what there called "
Ripon Yorkshire
 
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spec

Well-Known Member
Most Helpful Member
Actually the guy who is doing the chinese one is a fool and I suggest you watch it cause its not the way to do about fixing anything nor instructing anyone. Ripon Yorkshire
I have watched all the videos. Presumably you are referring to the video titled, 'Fix My Chinese Plasma Cutter'. The important thing is not the guy or how he talks but the fact that he is pointing out a common failure on that family of plasma cutters. It seems like some of the units have a botch which needs to be sorted for reliable operation.

I was expecting you to be from China.:) Care to put your location next to 'Location' on your user page. I was stationed at RAF Church Fenton, near Tadcaster, at one time.

spec
 
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b.james

Member
No sweat spec . Some of us prefer not to put a location in . There is enough of that going on in google and the states without giving them free advice . I guess you don't give your right name either huh?I see you ask "
Is anything true? I'd venture "Hope not on the internet for safety's sake"


Well I am pleased to report gleeful success !!
First thing I tried too as the fan was working so I checked the points at the front of the machine . There is a fairly high voltage air gap set which is part of the system . Cleaned the points with a points file and tried it without success so I thought to bring the contacts just slightly together , fired it up and away she went .All good so far
Thanks again
 

spec

Well-Known Member
Most Helpful Member
No sweat spec . Some of us prefer not to put a location in . There is enough of that going on in google and the states without giving them free advice . I guess you don't give your right name either huh?I see you ask "
Is anything true? I'd venture "Hope not on the internet for safety's sake"
I can understand your point of view.:)

Well I am pleased to report gleeful success !!
First thing I tried too as the fan was working so I checked the points at the front of the machine . There is a fairly high voltage air gap set which is part of the system . Cleaned the points with a points file and tried it without success so I thought to bring the contacts just slightly together , fired it up and away she went .All good so far
Thanks again
Good news: well done.:cool:

spec
 
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tcmtech

Banned
Most Helpful Member
Given that repair description I am almost half tempted to think that the machine you have may be a cheapened up copy of the old Thermal Dynamics Pak Master series being they used a spark gap based ignition circuit that would cause odd logic faulting issues if the spark gap got too far out of spec.

Either that or it's an older Esab unit knock off. They had that spark gap issue on a few of their machines as well.
 

b.james

Member
I find it just painful that someone, who has done nothing to help whatever , except post for the hang of it and cloudyies the water with his footprints then claims to have known all about the issue, all along.... after it is fixed note .

Just plain stupid, time wasting posting and it drives away others who may have something worthwhile to contribute.
 
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tcmtech

Banned
Most Helpful Member
Yea about that. I 've worked on enough machines to know the what and why of the troubleshooting process and thus that's why I asked you for specific voltage readings relating to the power flow through the machine early in the thread to which you did not provide.:(

Without that information all I could do is speculate and I am not a speculating person when it comes to repairing things I understand very well but do not have direct access or properly requested data for so all you got from me was 'garbage in gets garbage out' based responses as in, you provide nothing I can use I provide nothing you can use which is where the "which is it?" response came from being from the technical troubleshooting standpoint there will be no striking arc discharge at the torch head between it and the work if the ignition circuit is not working yet you obviously had it it so I too it that it was working.

However had you mentioned that your machine used a spark gap based ignition systems (which you did not) I would have advised you to clean it and adjust it to see if it changed the ignition striking arc appearance which could have lead to you getting your machine going at that point. :facepalm:

The pictures were done well but lacked any degree of purposeful clarity to the exact build design of your machine. I could not find anything in them that clearly showed it to use a spark gap based ignition system and you also never once mentioned it until the end when you got lucky and figured it out yourself. :(

Simply put, I asked you for specific information which relate to what is for me standard troubleshooting flow chart practices to which you did not provide so I put very little effort into trying to solve your problem. In my troubleshooting practices those who can not follow instructions and provide me with the information I need do not get to go to the next step in finding a solution to their problem. :facepalm:

As far as my attitude goes, well, if you dealt with as many people as I have who just like you can't follow instructions, give little needed information and then get all self righteous when they do stumble on to the solution to their problem ( and you most certainly did all of those) by more luck than anything, heck yea, you will start to realize where my attitude is coming from as well. :banghead:

BTW, if you ever come back here with another question about your machine or anything else I will put this thread and its outcome into consideration over helping you even if I know what the solution to you problem is right from the first post. You might get a solution in my first response or you may spend days/weeks working through the problem based on others speculations ultimately to end up with no answers that work while I sit back and consider how things ended in this thread. :oops:
 
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