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Old 180 SD HF stuck on

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  • Tweekster
    replied
    Originally posted by cruizer View Post
    Well there is a way to get around this little quirk, and that is to get a 24VDC relay (you can use an automotive enclosed type) single pull single throw.

    Splice into wire #4 to the new coil side of the relay

    Splice into wire #21 to the other side of the coil of the relay

    Cut wire #31, put each cut piece into the normally open sides of the relay.

    Presto, the hf will only come on when you hit the foot pedal.
    I'm at work and need to check my schematic....wouldn't that let the HF turn on with the peddle, but will it ever turn off once the weld is started?

    Leave a comment:


  • Tweekster
    replied
    Originally posted by ccawgc View Post
    If 7 and 8 are not shorted then your problem is deep in the pcb.
    I assume you are only getting HF and the welder out put is off.
    If the welder output can be turned on by remote control and the HF does
    not turn off in stick. this will help you narrow where to look.
    most of the parts are simple gates and op amps. just follow the direction
    of the arrows. the hardest part of this diagram is following the short cuts.
    If you want to measure voltages on the pc board you must first kill the HF.
    An easy place is to cut the but splice to the HF transformer. Replace it with an inline connector. The HF causes volt meters to act up. If you try to measure OCV with HF on it will kill your meter. Be careful and good luck.
    I killed the AC to the HF transformer right at the start, then put a cheapo meter across it to monitor it for a change.

    As soon as I turn the power on in either TIG mode the HF is on, the pedal still controls the welding output, but does nothing for the HF. The HF turns off in stick mode, the only time it ever goes off.

    Looks like I need to trace out the gates and opamps, and figure out the logic.

    Leave a comment:


  • cruizer
    replied
    Well there is a way to get around this little quirk, and that is to get a 24VDC relay (you can use an automotive enclosed type) single pull single throw.

    Splice into wire #4 to the new coil side of the relay

    Splice into wire #21 to the other side of the coil of the relay

    Cut wire #31, put each cut piece into the normally open sides of the relay.

    Presto, the hf will only come on when you hit the foot pedal.

    Leave a comment:


  • ccawgc
    replied
    If 7 and 8 are not shorted then your problem is deep in the pcb.
    I assume you are only getting HF and the welder out put is off.
    If the welder output can be turned on by remote control and the HF does
    not turn off in stick. this will help you narrow where to look.
    most of the parts are simple gates and op amps. just follow the direction
    of the arrows. the hardest part of this diagram is following the short cuts.
    If you want to measure voltages on the pc board you must first kill the HF.
    An easy place is to cut the but splice to the HF transformer. Replace it with an inline connector. The HF causes volt meters to act up. If you try to measure OCV with HF on it will kill your meter. Be careful and good luck.

    Leave a comment:


  • Tweekster
    replied
    Finally had a chance to get back on the troubleshooting.

    Circuit Board #190772

    Across RC1-7 and RC1-8 I got .5 Mohms/40+ Mohms forward and backwards, Q3 looks okay.

    Across pins 4 and 6 of OC1 I get 85 Mohms forward and backwards, that looks okay.

    Across pins 'S' and 'D' of Q5 I get 1.1 Mohms/infinity forwards and backwards, so that looks okay.

    It looks like pin 4 of the quad gate IC U6 triggers Q5, but I'm not very familiar with checking linear IC's, so that's where I left off.

    One thing I might add, is this occurred right after I moved into my new house, and the welder rode 700 miles in a U-Haul trailer. I'm not sure what components are vibration sensitive, or it was just a coincidence.
    Last edited by Tweekster; 04-04-2010, 05:03 PM. Reason: Added info

    Leave a comment:


  • Tweekster
    replied
    Thanks! I'll give it a shot.

    I'm a self taught audio amp guy, so these control circuits are a little new to me.

    Leave a comment:


  • cruizer
    replied
    Looks more to me that Q3 (opto triac) has shorted causing RC1-8 (115Vac) to go direct to RC1-7 which is the control tor the HF transformer.

    Could be wrong, but thats where I'd start looking. Just take a resitance off
    RC1-7 to R1-8, you'd know for sure. (power off of course)

    Leave a comment:


  • Tweekster
    started a topic Old 180 SD HF stuck on

    Old 180 SD HF stuck on

    5 years ago my 180 SD had the HF start stick on, and being in the middle of a project, I used that for justification to the Wife to buy a Dynasty 200 DX. The 180 SD has been in the corner ever since.

    A friend now wants to buy the old 180 SD if I can fix it. I have the 180 SD Tech Manual, and I am in the process of tracing the circuit back from the HF coil. In the interest of saving a little time, I was wondering if anyone else has seen this problem, and if you could help narrow down my troubleshooting?

    The HF start is on the minute I power the machine up, never turns off, and doesn't respond to the peddle. The peddle controls the amperage fine, and is the same peddle that I use with my 200 DX, which works fine. With the peddle unplugged, the HF is still on. HF Transformer T3 is getting constant voltage from the main PC1 circuit board. I haven'd taken measurements at the circuit board yet, but just looking at the circuit, it looks like it could be a shorted optoisolator (OC1) or shorted MOSFET (Q5).

    SN KK184429

    Any ideas?

    Many thanks in advance!
    Last edited by Tweekster; 02-13-2010, 11:43 AM. Reason: Added SN
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