Chinese Plasma machine repair

Discussion in 'General Electronics Chat' started by Ron B., Jul 4, 2009.

  1. Ron B.

    Thread Starter New Member

    Jul 4, 2009
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    Hi Folks, i have a real dillema here and it all revolves around a Chinese made 3-1 machine,welder,plasma cutter and stick welder.
    This machine uses hf start for the plasma and tig but as is per usual the hf start doesn't work.
    it uses a cockcroft -walton multiplier to work the hf start .This circuit has blown up two of the capacitors and there were two zenor diodes soldered together beside the other two . these were also blown ,
    What I would like to know is how I can modify this circuit to make it both work ( which it has never done,it's actually new ...:mad:) and be more reliable.
    Unfortunately the zenor's markings don't relate to anything at the local electronic suppliers and the capacitors are marked 102 -2kv .
    Two capacitors were blown apart also.
    I would guess this is the same board as used in practically all these sorts of machines but because the manufacturers pretend to not understand English I can't simply get another PCB. So it looks like I have to figure this thing out and get it to work.
    Thanks in Advance.:)
     
  2. Papabravo

    Expert

    Feb 24, 2006
    10,135
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    So we see that the ultimate cost of ownership must take into consideration the near impossibility of obtaining spare parts or service on that harbor freight piece of crap. I'm going out on a limb here but I think your chances of getting the thing to work again are vanishingly small.
     
  3. KMoffett

    AAC Fanatic!

    Dec 19, 2007
    2,574
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    So...
    = 0.001uF/2000V

    I tend to agree with PB on this. Harbor Freight tools should be considered consumables...they last as long as they last. When you pay the low prices they charge, you can't expect any big support inventory of repair parts taking up space, locking up assets, and accruing inventory taxes. Even the name brand stuff is getting hard to, or prohibitively expensive to maintain over the long term. :(

    I do buy stuff from Harbor Freight and Northern Tool, but nothing I can't maintain on my own or won't shed tears over when it bites the dust. ;)

    Ken
     
  4. Wendy

    Moderator

    Mar 24, 2008
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    No warranty from who you bought it from? Personally I think they owe you a new one, if it is a local retailer.

    The capacitors sound like 1000pf, or 0.001µF at 2KV.
     
  5. Ron B.

    Thread Starter New Member

    Jul 4, 2009
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    Not exactly the answers i was looking for.:(
    No,it's not a harbour freight item ( although if the various citizens of the world stopped buying chinese they would be reduced to eating their mac donalds by candle light)
    and as i said their is no chance of the supplier responding to any emails etc because of their lack of english and my lack of mandarin . I can supply factory addresses etc to those interested but that is not why I posed my initial question .

    This PCB appears to be just "nuts and bolts" circuitry ,nothing exotic or special about it. ( e'g ,capacitors are just that and $.0.0 each) and on the face of it could be compared with a 1950's motor car in terms of sophistication.
    What i really want to know is " how could i go about determining the zenor diode values and how to make it reliable by the use of better quality components " ?
    any help along those lines will greatly appreciated.:)
     
  6. Ruptor

    Active Member

    Apr 26, 2009
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    Hi Ronb
    Find equivalents or post the zener markings and replace them with higher voltage and current types. You could post a drawing of the circuit so we could see if it is correct or could be improved. I had problems with slow speed feed of wire for thin sheet metal welding and finally figured out it wasn't me. The drive was jittery and kept stopping the arc or feeding faster and causing holes. When I worked out the circuit it was obvious that the half wave supply to the motor was useless for low speed wire feeding so I bridge rectified it and added a smoothing capacitor. Now I can weld 0.6 mm sheet metal with ease and that's with no gas just the gas in the wire.
     
    Last edited: Jul 5, 2009
  7. SgtWookie

    Expert

    Jul 17, 2007
    22,182
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    Ruptor,
    He does NOT want to replace the Zener diodes with a higher voltage type.
    He needs to replace them with a higher wattage rated Zener.
     
  8. Ruptor

    Active Member

    Apr 26, 2009
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    You miss quoted me I said replace with higher voltage and current type.
     
  9. KMoffett

    AAC Fanatic!

    Dec 19, 2007
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    If it's a Zener diode (think voltage regulator), as the good Sgt. said, why would you want to replace it with a "higher voltage" type. Especially, without even knowing where it sits in Ron's circuit.

    Ron, a photo would really be good.

    Ken
     
  10. Papabravo

    Expert

    Feb 24, 2006
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    Without more relevant information on the circuit and the components it appears unlikely that the help you require will be forthcoming.
     
  11. mkbutan

    Senior Member

    Sep 30, 2008
    270
    16
    hi
    it doesn't matter what brand or mark or (from country) you bring any product
    OK now every body here know that it is a welding / cutting machine as Mr. Ron B
    A Chinese made 3-1 machine,welder,plasma cutter and stick welder.
    1
    . Welder
    2
    . Plasma Cutter
    3. Stick Welding

    1 study the phenomena of the Welding machine.
    2 study the phenomena of the Plasma cutter machine.
    3 study the phenomena of the Stick welding machine.
     
  12. Papabravo

    Expert

    Feb 24, 2006
    10,135
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    That is quite simply not enough. He has a specific unit which is non-functional and he must decide on an attempted repair or replacement of the unit. Assuming his time is worth something and there is an opportunity cost for not having the machine it rapidly becomes clear that a new machine is the most effective solution. Even if the information was available AND the components were available in small quantities at a reasonable price and they did not have to be shipped by a slow boat from Taiwan.

    You may or may not have noticed but in the last 40 years the retail electronics parts business has quite simply vanished because it is economically unviable.
     
  13. Ron B.

    Thread Starter New Member

    Jul 4, 2009
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    OK, I've been busy earning a living so the plasma debacle has been on the back burner. I have been looking further into this and I feel that the way the cockcroft walton circuit has been constructed is really a bit too light duty for a machine like this. OK for TV's and Microwaves I suppose so I have decided I will take a more boots and braces approach.
    In this picture the hf start arrangement is in the lower left. The multiplier circuit includes that transformer which in turn uses the diodes ( there are empty places on the board where the failed components were blown up :mad:)and capacitors in the CW setup.
    I am beginning to think the best way is use a an automotive coil spark plug and module to create the hf start and simply connect in to this circuit where the torch trigger activates the timer [which in turn activates the hf start and lets it runs for a few seconds ].
    Any thoughts on this? Cheers guys! :)
     
  14. Ruptor

    Active Member

    Apr 26, 2009
    44
    0
    The diodes look more like a bridge rectifier setup or could be a voltage doubler but either way they wouldn't be zeners. It doesn't look difficult to repair. Here is a simplel replacement arc circuit of a tig welder I found somewhere on the net. It might be of use.
     
  15. Ron B.

    Thread Starter New Member

    Jul 4, 2009
    7
    0
  16. Ruptor

    Active Member

    Apr 26, 2009
    44
    0
    Hi Ron
    Can't you find the circuit on the internet? I'm not great at internet searches but If you post the details of the welder maybe some else can find it for you. Otherwise I would draw the circuit that way you might be able to improve the design with just component changes. Usually the designs are borderline and putting some bigger components in can make it bomb proof. My welder feed motor has been perfect for 10 years now since the modifications.
     
  17. Ron B.

    Thread Starter New Member

    Jul 4, 2009
    7
    0
    I have spent the last week scouring the interweb looking for info.I have found several manufactures making the same machine with different names in both China and India. Great work if you can find it me thinks:D but no one has a proper circuit drawing with component specs listed. Hence the problem I have finding someone here ( Australia) who has enough nous to simply tell me that i can do 'this or that" and get the bugger running again.
    unfortunately the days of the local electronic repair guy have past thanks to throw away stuff.
    Strangely enough I ran several hundred coin op video games in the late 70's and I used to service all my own game boards ,but i knew what i was doing back then...:D:D.
     
  18. Slayr

    New Member

    Jul 6, 2009
    3
    0
    I've tried for several months to get info on these 3 in 1 machines with no luck. Aside from forums that talk about them their seems to be no repair parts that can be had. None found by me anyway. Got a Chiry 520D with a burned transformer on the top board just waiting for a hero to help it burn. Pics below if anyone knows anything about it. Transformer is EE25 200:6. Thanks.

    tig 9.jpg

    tig 4.jpg
     
  19. Papabravo

    Expert

    Feb 24, 2006
    10,135
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    Just as a point of reference I would be interested in knowing the original cost of the 3 in 1 machine. This might put the effort involved in attempting to repair it into some perspective. That the parts are marginally identifiable and possibly pure unobtainium certainly would give me pause about the attempt.
     
  20. Slayr

    New Member

    Jul 6, 2009
    3
    0
    I've got $175 in the Chiry 520D bought as-is non working. Also have another under the Lottos namebrand which works fine so far. The Lottos went for $450 on ebay but similar machines are from $435 up through $700 I've seen them go for. Most sell for around $565 or in the neighborhood. Maybe in the future there might be parts available and the Chiry isn't costing me anything to store till who knows.
     
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