L-Tec Heliarc 250HF High Frequency Start Problem
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  1. #1

    L-Tec Heliarc 250HF High Frequency Start Problem

    Hi everyone, I've been reading these forums for a long time but this is my first post. I'm a hobby welder, I got into welding few years back with a mig welder but after taking some night classes, I decided I want to dive into tig welding. Last week I bought a used L-Tec Heliarc 250HF Plus welder after successfully tigging both aluminum and steel in the sellers shop.

    When I got it home the high frequency had ceased to work. I cleaned the points and set the spark gap, still no luck. I can't see anything happening at the points. No sparks at all. I turned off the lights and gave it a go to see if maybe the hf was grounding out somewhere but I didn't see anything. The machine still stick welds fine, and I have both current control with the pedal and gas flow if I use the pedal while scratch start tigging on steel. I tried swapping out tig torches as well thinking my torch was bad and still no luck. I'm hoping someone has a thought about what I can test or try to get this welder up and running well again? Thanks for any and all help.

    Ryan

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  2. #2
    Join Date
    May 2015
    Location
    Corvallis, OR
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    116

    Re: L-Tec Heliarc 250HF High Frequency Start Problem

    Do you have the manual for the machine? Get one if you can. ESAB may have them online. You can email the tech support if you can't find a manual. I've had good response times from them recently. I just did a quick search for L-TEC Heliwelder 250 and came up with a manual from 1995, on ESAB's site.

    You mention setting the spark gap, was that spec from the manual? And what did you set it to? If you have the manual, there may be a section in the troubleshooting area related to no HF spark.

    Sounds like you have a good handle on the TIG procedure, but it doesn't hurt to list all your machine settings, or even a picture of the front panel for the TIG setup.
    Last edited by redbeerd; 03-27-2018 at 11:58 AM.
    AHP AlphaTIG-200X
    Miller Multimatic 215

  3. #3

    Re: L-Tec Heliarc 250HF High Frequency Start Problem

    Thanks redbeerd, I did get a manual for the machine. It said to set the spark gap to .025, I used feeler gauges to set it. I'll get a picture of my settings when I get home from work. Thanks again, -Ryan

  4. #4

    Re: L-Tec Heliarc 250HF High Frequency Start Problem

    Here are few pictures including the nameplate, a pic of the hf assembly and the machine settings. I have it set to A.C., HF set to continuous, balance and arc force roughly at the midpoint, and in tig mode. This was to weld aluminum. Here is the web address of the manual I have been using. Hope that link works.

    Thanks,
    Ryan


    https://www.google.com/url?sa=t&sour...noARl_ja__76L4


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  5. #5
    Join Date
    May 2015
    Location
    Corvallis, OR
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    116

    Re: L-Tec Heliarc 250HF High Frequency Start Problem

    Thanks for the manual link. It worked.

    Did you try TIG welding with the HF switch in START mode? Used for welding on steel. Try that first, then the following.

    So, on page 17 of the manual, section 5 Troubleshooting, part "J".

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    It sounds like you've tried the first 2 options. Onto the third if you haven't done so already. Hope you don't have to get to #4.

    And looking at the schematic on page 18, you'll notice that some items appear to have been written in by hand. I don't see on the schematic where the "HFS" (Hi Freq Switch) is. But, physically, it's on the front panel toward the top and has 3 positions, OFF, START, CONTINUOUS. Page 10 in the manual has a description of it. You should check that just in case. To test you should make sure machine is unplugged, then isolate the switch from any connections and test the switch and the wiring for continuity and resistance. But, since you are getting gas flow when in TIG mode, it sounds like the switch may be working, and there could be an issue with the "Logic P/C Board" p/n 675421. Which, I have no idea how it works, or if it's even available as a replacement.

    But, if you're in the machine already, you may want to look around inside for any obvious signs of things that don't look right, loose wires especially grounds, loose nuts/bolts, worn wires, dark or burnt looking spots.

    Good luck.
    Last edited by redbeerd; 03-27-2018 at 07:50 PM.
    AHP AlphaTIG-200X
    Miller Multimatic 215

  6. #6

    Re: L-Tec Heliarc 250HF High Frequency Start Problem

    Unfortunatey the hf does not work in the start mode either, it will still weld but only with a scratch start. I decided to dig a bit deeper this evening. The continous/start/off high frequency switch is physically mounted to the logic board. Because of that I decided to pull the board for a closer look. Before I could begin testing the switch I noticed a wire that had burned through its coating and then separated. I replaced the board and jumped the wire but still no hf spark.

    The burned wire is the green wire that connects one leg of C16 to the ground of the Remote Torch Receptacle (see Figure 5-2) photo attached for reference. I'm thinking about trying to replace C16 and then going from there unless you think there may be a more likely cause of that wire melting? No obvious signs of C16 (a ceramic cap) failure, I'm just guessing because it's the closest thing in the circuit. Hopefully I'm on the right track! Thanks


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  7. #7
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    May 2015
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    Re: L-Tec Heliarc 250HF High Frequency Start Problem

    Forgot to mention, if you try the HF in START mode only, on steel, you'll need to change the polarity selector switch over to DCSP (DC Straight Polarity), which is same as DCEN (DC Electrode Negative).

    EDIT: I didn't see your post before this was posted.
    Last edited by redbeerd; 03-27-2018 at 10:13 PM.
    AHP AlphaTIG-200X
    Miller Multimatic 215

  8. #8
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    May 2015
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    Re: L-Tec Heliarc 250HF High Frequency Start Problem

    Quote Originally Posted by ryankevans007 View Post
    Unfortunatey the hf does not work in the start mode either, it will still weld but only with a scratch start. I decided to dig a bit deeper this evening. The continous/start/off high frequency switch is physically mounted to the logic board. Because of that I decided to pull the board for a closer look. Before I could begin testing the switch I noticed a wire that had burned through its coating and then separated. I replaced the board and jumped the wire but still no hf spark.

    The burned wire is the green wire that connects one leg of C16 to the ground of the Remote Torch Receptacle (see Figure 5-2) photo attached for reference. I'm thinking about trying to replace C16 and then going from there unless you think there may be a more likely cause of that wire melting? No obvious signs of C16 (a ceramic cap) failure, I'm just guessing because it's the closest thing in the circuit. Hopefully I'm on the right track! Thanks
    The more I write a response, the more stuff I see other stuff that might be related. The following might be a bit out of sequence. I'll do my best to put it in the best logical order for testing. Just read it all first, and pick the easiest sounding thing to do first.

    Not sure why that green wire would burn up, I would think it would be pretty low voltage stuff there. This could be an indicator of other weak spots.

    I think I understand what you're saying. It looks like it's there to help protect/smooth out the signal from the RTR (Remote Torch Receptacle). If you have a decent DMM you can check the cap with it. The schematic on page 18 shows that C16 has a value of .02 micro Farads, if I can read that right, it's a bit blurry when printed out. I think this would help keep the signal "smoother" for when it goes into the LOGIC P/C BOARD. Not certain that cap alone would affect the TS switch in the pedal. But there are 2 caps there, C15 also at .02 micro F. Might be worth checking their values to make sure.


    How is the HFS connected to the LOGIC PC BOARD? Through hole soldered? Mechanical? It may be easiest to start with checks upstream at the foot pedal and work your way toward the LOGIC PC BOARD.

    Ultimately, you want to make sure that the signals from the foot pedal are getting where they need to go, which in this case looks like the LOGIC PC BOARD pin P4-2 (brown or red wire?, from pin C on RTR) and the SCR PC BOARD pin P3-2 (brown, from pin B on RTR).

    You can try testing the foot pedal. Not exactly sure what's inside there, may be best to open it up and check. Usually it's a simple open/closed (ON/OFF) switch and a pot. I think the pedal parts are "TS" (Torch Switch) and "FC" (Foot Control) on page 18. The TS portion related to the simple switch which should ultimately signal the contactor (or SCRs in this case) and or HF circuit to close and the FC portion related to the pot that controls the current.

    I would meter out the FOOT PEDAL at the plug end for continuity and resistances. You should also be able to bypass the switch in the pedal with any similar rated switch and the correct wiring, but you could probably jumper it too at the receptacle (RTR) to test out if there was doubt. Be careful, not sure what kind of voltage/amps you've got on that circuit.

    You could just jumper that RTR switch (quickly, not permanently) between "B" and "C" which would simulate the pedal moving down, and signal the LOGIC PC BOARD to start the HF. This would eliminate the foot pedal circuitry quickly.

    You can see in that schematic pg. 18 that if the Torch Switch "TS" (not TS1, TS2 which are Thermal Switch 1, 2, etc.) was closed, it would complete the circuit to the LOGIC PC BOARD. I also see 3 thermal switches on that same path, TS1, TS2, TS3, which are all in series. So if one of those were to "open" it would open the entire circuit to the LOGIC P/C BOARD. Can you find and/or check these thermal switches? It looks like they're scattered about, such as TS1 part of MTR, TS2 part of HRTR? (hard to read the acronymns). They may look like a small diode or larger resistor, but have different markings. If they get too hot they act like a fuse and open. Not sure if these will reset when they cool. I've had one go out on my dishwasher twice in the last 6 months, and had to order new ones.

    Hope this long technical write up comes across as readable. Ask questions if needed, or post pictures if it helps.
    Last edited by redbeerd; 03-27-2018 at 11:47 PM. Reason: wire color update
    AHP AlphaTIG-200X
    Miller Multimatic 215

  9. #9

    Re: L-Tec Heliarc 250HF High Frequency Start Problem

    Time for bed now but I did verify the 3 position switch is working properly so now I think the possibilities are either:

    1. The logic board is bad (though every component that I could test while it was out at least had some continuity, diodes caps and resistors)
    2. A part of the high freq generation circuit itself failed
    3. Something with C16/The burnt wire situation ...I'll replace c16 next, fix the burnt wire and go from there.

    This is getting fun haha but I really hope it is something simple/cheap to fix otherwise I have a really big stick welder in the garage with a water cooler lol. Let me know if anyone has any other thoughts. Ryan




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  10. #10

    Re: L-Tec Heliarc 250HF High Frequency Start Problem

    Just saw your post thanks I'll go through it tomorrow and report back -Ryan

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  11. #11
    Join Date
    May 2015
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    Corvallis, OR
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    Re: L-Tec Heliarc 250HF High Frequency Start Problem

    You mentioned the HF circuit itself, did some diagram review and just now noticed the CB (Circuit Breaker, 15A) that's on the back of the machine toward the top. Looks like it's tied into the HF circuit, and even runs through the LOGIC PC BOARD and the HF contacts, which is different than the SG (Spark Gap). That'd be an easy thing to check, and probably should have been the first or second thing to check. The CB is also tied to the 115VAC duplex outlet on the back. So if the breaker was tripped, you wouldn't have power there when the machine was on.

    Also, I'm seeing some easier ways to check portions. Not plugged in, you could meter (continuity check) the RTR pin C to the LOGIC PC BOARD to make sure all 3 Thermal Switches are in tact. And you could meter RTR pin B to the SCR PC BOARD pin P3-2 (red wire) to check that length. You could probe B and C on RTR and step on the pedal to make sure the pedal switch is working.
    AHP AlphaTIG-200X
    Miller Multimatic 215

  12. #12

    Re: L-Tec Heliarc 250HF High Frequency Start Problem

    When I woke up I saw your post about the circuit breaker being in the loop. The breaker was tripped. I reset and hit the pedal and the hf fired! I just started laughing. Sometimes it is something simple. Hopefully there aren't any other demons that caused the breaker to trip, but right now I'm optimistic. Thanks so much for your help with this! I have a late night at work today but either late tonight or tomorrow evening I'll put the machine through its paces and confirm everything is good. Thanks again!
    Ryan

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  13. #13
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    Re: L-Tec Heliarc 250HF High Frequency Start Problem

    Yup, sometimes it's as simple as the circuit breaker (next to the 115VAC outlet on the back panel that is tied into the HF transformer circuit).

    Section J in the manual about troubleshooting should have this item listed as the #2. "15A circuit breaker on back panel is tripped. Reset breaker." You may want to actually write that in there.

    But, at least it got you looking around and thinking about the machine operation. Good find on that RTR ground wire.

    Hope you get some good years of use out of that machine.

  14. #14

    Re: L-Tec Heliarc 250HF High Frequency Start Problem

    Quote Originally Posted by redbeerd View Post
    Yup, sometimes it's as simple as the circuit breaker (next to the 115VAC outlet on the back panel that is tied into the HF transformer circuit).

    Section J in the manual about troubleshooting should have this item listed as the #2. "15A circuit breaker on back panel is tripped. Reset breaker." You may want to actually write that in there.

    But, at least it got you looking around and thinking about the machine operation. Good find on that RTR ground wire.

    Hope you get some good years of use out of that machine.
    Just wanted to post a quick update and say that the welder has been working great. I've put about 10 hours on it in the past week or so and it is awesome. It is a huge upgrade for me in terms of capabilities (coming from a scratch start tig rig using a small Hobart buzz box). Thanks again for the help diagnosing the issue, I learned a good lesson about checking the simple stuff first.
    -Ryan

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  15. #15
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    Re: L-Tec Heliarc 250HF High Frequency Start Problem

    Good to hear. Hopefully you can get another decade out of it, at least.

    Yea, it took me a while to learn to look for the (real) simple stuff. But, the more you do it, or don't, the more you'll learn. Either, the easy way or the hard way.
    AHP AlphaTIG-200X
    Miller Multimatic 215

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