Century Mig Welder Problem

Reply

  #1  
Old 07-09-05, 11:54 AM
klamham
Visiting Guest
Posts: n/a
Exclamation Century Mig Welder Problem

Hello There, A Newbie to the site. I have a Century Mig Welder, Wire Feed Model # 117-052-001 I have had this machine for about 10 years and it has served me well. My problem is that it has stopped working. It just sparks now when I go to use it, no constant current and wire melting. The tip is not grounded and the fuse is good. I have tested the the feeder hose and nozzle and they are good. The fan is working and I hear the relay click when I push the trigger, and wire comes out. How to procede from here to trouble shoot is the question? How do I test the Capacitor and the transformer? I paid $580 for the machine when I bought it and was wondering if it is worth fixing or not. Any help with these problems would be greatly appreciated. Thank You Kevin
 
Sponsored Links
  #2  
Old 07-09-05, 04:59 PM
G
Member
Join Date: Oct 2004
Location: USA
Posts: 719
Received 0 Votes on 0 Posts
80% of time the diodes go bad. can be $20.00 depends on how they mount.
Depending on how they go out, they can take out the Capacitor or blow it up. no joke.

First I need a description of the machine
120v or 220v ?
Is it the big square Box style?
Is the wire feed unit on top ?
Is the heat selector variable or 5 preset settings ?
Is the Gun Hot/powered all the time or only when you pull the trigger ?

Its less then a 10% chance that the CAP is causing the problem, but it can be bad.

Transformer ?
If it smells burnt or if the varnish comes off, maybe. but its rare that you would get any sparks from the Tip.
 
  #3  
Old 07-13-05, 12:33 AM
klamham
Visiting Guest
Posts: n/a
Exclamation Century Welder Problems

Thanks for the reply. The machine is a 120 volt, 90-105 amp. The amps are set by rocker switch on front, and the temp is variable potentiometer type knob also on front. The cabinet is box type, narrow front, long sides. The wire is horizontal mount on top inside cabinet. The gun is turned on only when you pull trigger. No signs of burnt or smell of transformer. The machine only makes weak spark when trigger pulled. Circuit board is easy to get to and there are no signs of cracked or burnt diodes or resistors. I am told I would be better off getting new machine. I would rather fix this one since I built cart and have argon set up in place. I would also like to save the 5-6 hundred a new machine would cost. I am in a wheelchair and would like to save the money for other things. I am used to working with this machine and know its limits. It only has a 20% duty cycle, but I really do not go crazy with it. Like I said I have had it for 10 years and am used to it. I feel I am capable of repairing it with some help. I am a little concerned about your comments about the capacitor blowing up though. We don't want that do we!!! Thanks Kevin
 
  #4  
Old 07-13-05, 08:48 AM
IBM5081's Avatar
Member
Join Date: Oct 2004
Location: Texas
Posts: 655
Received 0 Votes on 0 Posts
Even the name-brand 110-volt MIGS have just a 20% duty cycle as well.
 
  #5  
Old 07-13-05, 07:33 PM
G
Member
Join Date: Oct 2004
Location: USA
Posts: 719
Received 0 Votes on 0 Posts
The reason I wanted a description I have some manuals, but not the same.

What the diodes do is change the AC from the Transformers output into DC output.
That capacitor can only work with DC if it was to get full AC from shorted Diodes It can Blow up.
your cap is in one piece, most of the time it will be ok.
=========================
I would check the diodes first. that's a 80% chance that they are bad.
Most of the time the welder company's not just Century, install Diodes rated at lower current/amps then the machine.
Your machine is 105 amp, I would say they have 70 amp diodes inside.
another words the more times you go over the duty time the more stress on the diodes.
==========================
Caution:
That capacitor can hold a charge for a long time, they place a resistor across the capacitor to discharge the cap.
Its rare, but if that resistor is bad that cap may be holding a charge.
The resistor is about 2-1/2" long may be brown.

Before you do anything unplug the welder from the wall.
put some safety goggles on and short across the two capacitor terminals with a screw driver Twice.
if the resistor is bad you may get some large sparks.
you may not get any sparks with your current problem.
============================
This is a good guess, that you have two Diodes that are mounted on a large heat sinks maybe two metal plates.
also a thermal cutoff switch.
one end of each diode will be connected to the Transformer.

You will need to disconnect one end of each diode for checking (you cant check them in circuit)
If you have a multi meter you can check them, if it has a diode check position that will be better.

Or take the diodes or the welder to a TV shop ask them to check the diodes, it will take less then ONE minute to check them.

===========================
I don't know if you have standard off the shelf diodes you may need to call "Lincoln welders for a new set"
If the diodes are threaded into the heat sink you should find some off the shelf diodes for $20.00
I have two Century welders with off the shelf diodes inside them.

look at the diodes for part numbers printed on them.
Let me know the part numbers.
let me know if they are threaded.

Do you have a wiring diagram ?
 
  #6  
Old 07-14-05, 11:30 PM
klamham
Visiting Guest
Posts: n/a
Exclamation Century Welder Problems

Hey GWIZ, Thanks for taking the time to run through these problems with me. I really appreciate your help! Well I see the big resistor that you mentioned and the capacitor has two 3/8 nuts for the connections on top. The cap is about the size of a cars coil. I will be sure to discharge it before going any further. I did not see the diodes on any heat sinks, only on the circuit board. I will look closer tomorrow and see if I can find any that are mounted on heat sinks. The thermal protector has two leads and using my meter I see it still gets current through it, so I assume there is no problem there. As far as having any manuals, no I do not have any. I only have the schematic that came with it, but no component values. When I lift one end of the diodes from the board and test them, what should the setting on my meter be on? DC or AC with the battery sending current for testing? I am now pretty sure that you are right and that it is the diodes. I use the machine for working on my 1970 Dodge Dart and my 1991 Ford handicapped van. I just got the van and need the welder to put the floor together in it. I am sure that I have pushed the duty cycle more than once. I see some of the posts have pictures loaded to them, I am not sure of how to do it yet but when I do I will load some digital shots for a better view of the welder. Well have to go and again , THANK YOU for the help. Kevin
 

Last edited by klamham; 07-14-05 at 11:43 PM.
  #7  
Old 07-14-05, 11:50 PM
G
Member
Join Date: Oct 2004
Location: USA
Posts: 719
Received 0 Votes on 0 Posts
" The thermal protector has two leads and using my meter I see it still gets current through it,"

How are you testing the thermal OL.
It should be mounted on the heat sink with the diodes.
 
  #8  
Old 07-14-05, 11:58 PM
klamham
Visiting Guest
Posts: n/a
Exclamation

Hey GWIZ, I used my meter on dc volts and tested it that way. On the dc 10v setting? I am pretty sure the diodes are on the board and there is a quick disconnect plug on it to take it out. I see on the scematic that there appears to be3 diodes and 2 resistors and a small cap and some other pieces. I am sitting in my bed right now so I am not sure of the layout. I can see it tommorow and check for sure.
 
  #9  
Old 07-15-05, 12:11 AM
G
Member
Join Date: Oct 2004
Location: USA
Posts: 719
Received 0 Votes on 0 Posts
I don't have a drawing but I think the OL runs the 120 volts AC like a fuse.
A picture of the wiring diagram would help.


You use your Ohm meter to test the diodes.
remove all power from the welder and the (Cap discharge it)
set your meter on the 20K ohm scale.
remove one end from the diode.
place leads across the diode take a reading, reverse the leads take a second reading.
one reading will be hi and the other will be low.
if the readings are the same the diode is shorted (bad).
no reading its open, or your meter just cant test it.

I will post a link on how to test a diode when I find it.
 
  #10  
Old 07-15-05, 12:21 AM
klamham
Visiting Guest
Posts: n/a
Exclamation

Hey GWIZ, You are the best! I am sure the diodes are on the circuit board and testing them will be no problem. I can understand the hi-low readings and the open part, but why would my meter not be able to read them? I do not work on it with the power connected since I do not want to light up! I have not figured out how to attach pictures to the post, do you know how? Then I could take pictures and scan the scematic into the post and you would have better idea of what I am up to. Thanks Kevin
 
  #11  
Old 07-15-05, 12:33 AM
G
Member
Join Date: Oct 2004
Location: USA
Posts: 719
Received 0 Votes on 0 Posts
Just trace the two large wires from the transformer to the diodes.
The diodes need to handle 70 amps the wires will be large.
only 2 diodes or 4, not 3 that's for something else.

They will not plug in.
They will not be on a circuit board. they get HOT. must be on a metal heat sink.

Some meters don't put out over 2 volts on the ohms scale
the diodes need about 2 volts just for a basic test.

Send me a PM with your Email address then you can send me the pictures.
PM (Private massage).
 
  #12  
Old 07-15-05, 12:59 AM
klamham
Visiting Guest
Posts: n/a
Exclamation

I looked at the scematic and it shows 4 black wire coming out of transformer going to 4 diodes on the circuit board. Then ou the other side of the transfomer are 4 white wires going to 4 diodes on the other side of the circuit board, looks like a total of 8 diodes. Thanks Again Kevin Send the other info later today, by E-mail
 
  #13  
Old 07-15-05, 01:18 AM
G
Member
Join Date: Oct 2004
Location: USA
Posts: 719
Received 0 Votes on 0 Posts
Page 42 diode testing

Big book may be 500 pages 20 min to down load.

Down load Vol III semiconductors
http://www.ibiblio.org/obp/electricCircuits/index.htm

http://www.kpsec.freeuk.com/multimtr.htm
 

Last edited by GWIZ; 07-15-05 at 01:29 AM.
Reply
Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: