Ranger 250 K1725-2 Problem
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  1. #1
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    Unhappy Ranger 250 K1725-2 Problem

    Hello; I just joined this site. I have a tech problem with my Ranger. Its been loosing welding current. I had to keep turning up the dial for the same current setting. Now I can't even stike an arc. I opened up the machine and took some voltage readings. I get 90vdc at the rectifier output and input to the chopper. But only 19vdc at the chopper output and the welder cable lugs. I assume its suppose to be 28vdc at full current? And the voltage should vary with the current control pot? It remains at 19vdc and does not vary. This machine only has 45 hours on it. I paid $3500 new for it back in 2001. I have seldom welded with it (maybe 25 hours of welding) and was mainly used for emergency standby power on my home. The aux 240vac side works just fine. So I am thinking maybe the welding control board went dead or the chopper board is the problem? Any ideas? Does anyone know how much the parts will cost? I am very disapointed with Lincoln.

  2. #2
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    Re: Ranger 250 K1725-2 Problem

    Welcome to the forum technoid and I'm sorry to hear of your misfortune. I know this doesn't help solve the problem but while serving as Warranty Administrator for a major fire apparatus manufacturer years ago, I read somewhere that if an electronic device is going to fail, it's likely to occur within the first 50 hours of operation - right where your unit happens to be. You posted the model# in another thread but do you have the code#?

    That said, it does sound like a potential board problem although a long shot could be a dirty output control potentiometer from. . . lack of use. I might suggest a call to the Lincoln tech department on Tuesday to get their take on it. They can offer whatever checks are required to narrow down the cause.

    I understand your frustration but assure you Lincoln has a well established reputation for building quality products and offering excellent support of same.
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  3. #3
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    Re: Ranger 250 K1725-2 Problem

    Thanks for the reply. The code is 10854 and serial # U1020335733. I did go to the Lincoln service site online. I sent them my info and I am waiting for a reply. My frustration against Lincoln stems from being in the middle of a welding project on my truck when it stopped dead. Left with the rod glued in place. To give you a little back ground on this machine. It was always kept indoors in a dry location. I ran it each month or so for about 1/2 hr to give it exercise. I don't think its a dirty pot. The pot is the sealed type. I have an electrical back ground in generator repair. I use to work on industrial 3 phase 480v units. The welder is simular in design but of course different after the prime mover. Current control seems to rely on the solid state welder board. I am not familiar with chopper design but from the sound it made during an arc there is a frequency mixed in the DC involved with it. Some of Tesla's ideas in action, ha ha. But anyway I'll let you know what Lincoln comes up with. I just hope its not an expensive fix.

  4. #4
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    Re: Ranger 250 K1725-2 Problem

    In re-reading your original post I maintain there's a good chance it could be a board problem which would include the 300A output diode module (chopper). I'm not familiar with these units so I dont know if the SCR drivers are on the diode module PCB1 (I suspect they are) or on the weld control board PCB3 but you could look for evidence of failed components on those.

    If the machine experienced a major component failure, my guess is one SCR failed which overloaded the other causing it to fail as well but it's just a guess. Lincoln tech support should be able to assist in checking them out if things point to that.

    It's a long shot but did you check the security of harness plugs P50/J50 at the diode module and P12 at weld control pc board PCB3? Pay particular attention to the pins for circuits #23 and #25 at P12. Also check plugs P41 and P42 at the analog power pc board PCB2 and P13 at weld control pc board PCB3. Look for the usual - corroded/tarnished/loose pins that prevent good contact.
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  5. #5
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    Re: Ranger 250 K1725-2 Problem

    I want to thank you again for your troubleshoot advice. What I thought was a through the wall wire gromet was actually a plug. And it was one turn loose. These are the wires going directly to the chopper SCR. I got it to strike an arc again but the current level of the weld does not match the dial. It still does not put out the full 250 amp. More like 125. I tried burning a deep bead on a piece of 1/4 angle steel. At 250 amp It should have blown holes through it. So I think I might be firing on only half the chopper. Or something else is wrong. I put an attachment of a few views inside the welder. All the other plugs have been sealed with silicon from the factory. The chopper board is sealed with a clear hard silicon. No sign of any burning on any of the boards. So now at least I can finish up on my truck. And wait to see what Lincoln can do for me.
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  6. #6
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    Re: Ranger 250 K1725-2 Problem

    Must be talking about plug P50 and jumper J50. I'd have to say you have a failed SCR or driver circuit for one side of the 'chopper' unit as you stated. Determining which one (SCR or driver circuit) and which side would require the assistance of Lincoln tech of someone like member ccawgc that would be more familiar with these units.

    Please keep us posted.
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  7. #7
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    Re: Ranger 250 K1725-2 Problem

    Ok thanks. I'll try to get in touch with ccawgc

  8. #8
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    Re: Ranger 250 K1725-2 Problem

    Quote Originally Posted by technoid View Post
    Ok thanks. I'll try to get in touch with ccawgc
    I got an answer from ccawgc. Here is what he said......

    First get a very good multi meter That can read milli volts. And a current meter Dc clamp on. Check the diagram and parts list and find the current shut that is in series with the weld terminal. Check the diagram see if the shunt is a 500 amp / 50 mv type. Or a different rating. You can call Lincoln if you can't find it, have your code and serial number if you call. If you have the 500 amp shunt. You will have a reading like this. Use long weld cables and short them together. Use a welding rod as a fuse. Turn output on and up. make a reading on the shut. 250 amp will give you 25 millivolts. A 400amp shunt will give you 25 millivvolts at 200 amps. Make sure the correct voltage is making it to the control pc board. Make sure your test is short or the rod will melt in two. If your clamp reads 125 and the dial is set at 250 and the shunt voltage is 25 millivolts. the shunt is bad. Do the math on the shunt. If the shunt voltage is correct then there might be a problem with the control pcb or chopper. Start with the shunt, they do go bad and they cost a lot less that the chopper or control pcb.

  9. #9
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    Re: Ranger 250 K1725-2 Problem

    how muck lead and ground do you have on it . try to and clean the brushes on it

  10. #10
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    Re: Ranger 250 K1725-2 Problem

    Quote Originally Posted by brent t View Post
    how muck lead and ground do you have on it . try to and clean the brushes on it
    Thanks for your input. The cables are 50 ft long. Ends and crimps in excellent shape. The slip rings and brushes are clean. Only 45 hrs time on this machine. I called Lincoln today and they gave me some excellent tests to run. 400 amp shunt produces 50 mv at 250 amp. From 0-250 amp the milivolts should be linear going 1mv per 8 amps. The second check was to pull the J2 plug off. That causes the machine to stay in CC mode. That test checks for it being stuck in tig mode. The control pot is 10k and should be linear all range. If this all passes then I have to call them back for further spots to test. I'll keep every one posted on what I find. I am very satisfied with there tech service support. Anyone who reads this thread and needs tech advice from Lincoln can call 888-935-3877. Have your model, code and serial# handy.

  11. #11
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    Re: Ranger 250 K1725-2 Problem

    Well one thing's for sure - you'll really be getting to know your welder inside and out.

    Glad Lincoln tech is coming thru for you. I take it they don't suspect the 'chopper'?
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  12. #12
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    Re: Ranger 250 K1725-2 Problem

    On any lincoln welder that has a shunt and has low output. the first thing I check is the shunt . put the welder on the load bank with my certified meters and check the shunt.
    I have found to many welders that won't putout max current that have a bad shunt.
    What happens is, the shunt develops micro fractures in the silver solder it is put together with and the resistance is changed. More ohms means more voltage to the control pcb.
    You can set the welder for 250 amps and only get 150. The control pcb is getting a single from the shunt that that says 250 amps. So all you get is 150 amps.
    I have had these shunts fall apart after removing them.
    control pcb's work best if all inputs are correct.

  13. #13
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    Re: Ranger 250 K1725-2 Problem

    Makes perfect sense. I take it the power control board compares weld output (shunt input signal) to power control pot input signal and controls the 'chopper' diode module accordingly.
    Last edited by duaneb55; 07-07-2010 at 01:19 AM.
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  14. #14
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    Re: Ranger 250 K1725-2 Problem

    Quote Originally Posted by duaneb55 View Post
    Makes perfect sense. I take it the power control board compares weld output (shunt input signal) to power control pot input signal and controls the 'chopper' diode module accordingly.
    The most interesting thing from the Lincoln tech was how the machines control board can lock itself into Tig mode. When I told him I get 12vdc at the welding lugs no matter where I set the dial, he said it might be tracking. So by pulling the J2 plug it will default to CC stick. But this past 2 days have been in the high 90's outside. To hot to even walk out to the garage. So I will get back to this after temps return to liveable levels.

  15. #15
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    Re: Ranger 250 K1725-2 Problem

    80 by eight and 90 by nine is the norm down here this time of year and the humidity runs in the lower 90% as well. Thing is, it seems we're getting your weather while your getting ours.
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  16. #16
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    Re: Ranger 250 K1725-2 Problem

    Update...I got back into it this morning while it was cool for more tests. One of the tests ruled out switch and board tracking problems. Jumping out the board pins- and reading voltage across the cables- CC stick reads 77vdc, Pipe reads linear 0 -30 vdc, tig mode 11 to 12vdc. All normal. Linear tracking of the current to the mv readings from the shunt matched specs up to 160 amps. But thats with the dial at 250amp. The tech said the machine thinks there is an output short so it backs down on its current output. I have the Lincoln techs scratching their heads on this one. With the welding cables shorted using a rod as a fuse, the shunt input to the welder board is pulled, the welder does go to full output ( clamp reads 300amps very brief but then the engine surges trying to cut back). To fast to get a stable MV reading on my Fluke from the shunt. So now since I do not have a load bank I was told to connect a long run of #2 cable coiled up for some resistance. They want to know the mv's when it hits 300 amps again. The tech thinks it might be just a bad shunt. Or there may be more than one issue going on here. They don't want to rule the board being bad till all other possible checks are done. These guys are good. A new board costs $800! It got to hot outside so I will continue this again early in the morning.

  17. #17
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    Re: Ranger 250 K1725-2 Problem

    check your math on the shunt. a 400 amp shunt read 50 mv when 400 amps are going through it. 160 amps should give you 20 mv. if you are getting 50 mv at 160 amps the shunt is bad. the welder will phase back only if the shunt voltage is to high.
    yes duaneb55 you are correct. about the shunts function.
    in cc mode the shunt is used to control the output. in cv mode it is only used to protect the welder from over current problems.
    keep digging

  18. #18
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    Re: Ranger 250 K1725-2 Problem

    Quote Originally Posted by ccawgc View Post
    check your math on the shunt. a 400 amp shunt read 50 mv when 400 amps are going through it. 160 amps should give you 20 mv. if you are getting 50 mv at 160 amps the shunt is bad. the welder will phase back only if the shunt voltage is to high.
    yes duaneb55 you are correct. about the shunts function.
    in cc mode the shunt is used to control the output. in cv mode it is only used to protect the welder from over current problems.
    keep digging
    up to 160 amps it was 20 mv. Yes on the 400amp = 50mv. The linear action is 8amps = 1mv. It will follow with correct linear action right up to 160amp. What the Lincoln tech is trying to find out is why the machine is holding back its full output. So thats where we are at now. A load bank would be nice but I have to improvise using long #2 wire. Shorting the cable with a rod won't work long enough to get a reading on the Fluke meter. When you pull the shunt wires the machine does jump up to 300 amp causing the engine to hunt rapidly. I should see 37.5 mv but won't hold it stable for the mv reading. So the tech at Lincoln wants me to add resistance to the short to bring it down enough to get a good full output reading from the shunt. If thats ok, then he has other tests for me.

  19. #19
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    Re: Ranger 250 K1725-2 Problem

    Final test complete. With 50' of #4 for a load and the shunt wires pulled, the machine opened up to 270 amps and 33mv's. The shunt is good. Its come down to a bad weld control board. $877.00 new. So I called a local Lincoln repair shop. He is looking around for a used board. The other option is I can try to fool the weld board by placing a pot in series with one of the shunt wires for more current output.

  20. #20
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    Re: Ranger 250 K1725-2 Problem

    Quote Originally Posted by technoid View Post
    Final test complete. With 50' of #4 for a load and the shunt wires pulled, the machine opened up to 270 amps and 33mv's. The shunt is good. Its come down to a bad weld control board. $877.00 new. So I called a local Lincoln repair shop. He is looking around for a used board. The other option is I can try to fool the weld board by placing a pot in series with one of the shunt wires for more current output.
    update...I put a 1k pot in series with one of the shunt wires. As soon as 1 ohm was tuned in the machine would just jump up to 270amps. So there was no way to fool it into a normal linear current output. Then later on during welding at 125 amps the machine just quit welding. Its on its way to a Lincoln dealer this week for repair.
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  21. #21
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    Re: Ranger 250 K1725-2 Problem

    Quote Originally Posted by technoid View Post
    update...I put a 1k pot in series with one of the shunt wires. As soon as 1 ohm was tuned in the machine would just jump up to 270amps. So there was no way to fool it into a normal linear current output. Then later on during welding at 125 amps the machine just quit welding. Its on its way to a Lincoln dealer this week for repair.
    Well its confirmed. The welder board is the culprit. I should get the machine back next week along with a maxed out credit card.
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  22. #22
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    Re: Ranger 250 K1725-2 Problem

    OUCH! Sorry to hear it wound up being the main board.

    It IS a 9yo unit but perhaps if you plead your case with Lincoln based on the low hours, maybe just maybe they'll cut you a break on the cost of the replacement. You can ask the shop to go to bat for you but I'd go directly to Lincoln Customer Service and give it a try. One never knows.

    Oh yeah - don't forget to ask for the old board back too.
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  23. #23
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    Re: Ranger 250 K1725-2 Problem

    Quote Originally Posted by duaneb55 View Post
    OUCH! Sorry to hear it wound up being the main board.

    It IS a 9yo unit but perhaps if you plead your case with Lincoln based on the low hours, maybe just maybe they'll cut you a break on the cost of the replacement. You can ask the shop to go to bat for you but I'd go directly to Lincoln Customer Service and give it a try. One never knows.

    Oh yeah - don't forget to ask for the old board back too.
    Thanks for the advise. I called Lincoln. Because of the age of the machine he said there is a slim chance. But if this was a common problem with this early model they might consider it. They will be getting back to me. Thanks again for giving me the idea to call.
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  24. #24
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    Re: Ranger 250 K1725-2 Problem

    Quote Originally Posted by technoid View Post
    Thanks for the advise. I called Lincoln. Because of the age of the machine he said there is a slim chance. But if this was a common problem with this early model they might consider it. They will be getting back to me. Thanks again for giving me the idea to call.
    Its fixed! Great job from Kevin Gardner at Quality Welding supply Corp in Elmira, NY! Nice repair shop and supply store. Kevin repairs all makes and models of welders. I had a very good time talking tech with him. And best of all was Lincoln gave me 25% off the price of the replacement board. I highly recomend Kevins business to all welders in trouble.
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