Question about PCB and reliability

admin

Happy August everyone. I'm (still) eyeballing a Thermal Arc 211i and have read a lot of good reports on their other models.  I got to wondering about the circuit boards - I know nothing about electronic circuits - and wondered what the general experience is with inverter machines when it comes to reliability of the PCBs and the cost to replace if one blew.  Any thoughts?Also, the parts list and diagram on the TA 211i has four of them: one each for power, control, display and spool gun.  Am I right in thinking that's somewhat better than a single board in that it's cheaper to replace one of 4 boards than one big one if it smokes?Much appreciated if anyone has thoughts on this.  The TA price at cyberweld is making it tempting.  thanks
Reply:I blew out the mosfets in an inverter I have after it was accidentally dropped, and nobody local was eager to do the work,and I did not want to ship it out for repair, so I waited till I had time in winter and started checking circuits with a good digital multimeter, and found that it as a K75T60 mosfet which is a fast high power transister, and suspected a couple of diodes and the capacitor in that ladder circuit, as they were charred,(exploded) a good indicator of damage.But they cleaned up with alchohol and tested ok.I used desoldering braid soaked in flux to desolder then put the new mosfet in.The circuit was over designed-well to save the other components from damage.My cost was about $10.00 for the mosfet, so I bought a spare.When it comes down to descrete electronic components I don't think their is a single person out their capable of welding that cannot do the repair I did and would not require the replacement of the board it was on, like you suggest.If the machine works good for the first week you are likely going to get alot of good service from it as any faulty quality control issue will become apparent quickly.But capacitors do leak the insulating materials from them over time, doesn't matter who made it.I think your worries about inverters are unfounded, as long as you don't abuse them their ok.The only way you can get the advanced features/waveform is with an inverter.Here is a look at the parts.Oh and total cost with spare and wire transfer and shipping about $60.00 Also note all the mosfets to increase voltage. Attached Images
Reply:I'm always amazed at the intelligence and education on this forum. Many thanks Pistolnoon for the info and reassurance that most problems will come up soon if there is one. I personally should never get near a circuit board (I couldn't tell you a transistor from a resister from a diode), but it's nice to know I could probably find someone who can.  Or, time to order one of those kid's "make a radio" hobby kits and learn!
Reply:The TA is a fine machine and likely uses newer versions of switching transistors IGBT's which puts many of the older components all in one package.I have a TA 190 mig and it has never given me any problems, welds smoothy, controls feel tight, not sloppy and I think is made more durable than the Millermatics, ie screw on nozzles on torch, rubber not plastic wheels, screw on drive wheels.I have hated using older Millermatics after having my own Thermal Arc.If you are buying it for use of the tig feature you may be better off with a stand alone Tig machine because it has no high frequency just lift arc start.Price point is excellant.best
Reply:Once again, thanks pistolnoon.  I'm considering it to consolidate into one machine.  The tig to replace (sort of, there's no real replacement) my OxyAcet for thin material, also replacing a Hobart 140 and getting more amps, and of course the stick feature replacing a ginormous Idealarc tombstone taking up a lot of space in my garage. I got a good deal on a gentleman here on a HP 30 plasma, so I'd have two fairly portable and smaller machines to replace three.The downside is if the thing goes down, there's no backup, but I'm just a hack home welder.  Well there's another downside - I am romantically in love the Lincoln and my Smith torches.  sigh....
Reply:It is a bit of a catch 22,   you need more electronics for and inverter so more chance of electronic failure.  component quality is important and where u see difference between a TA and a Chicom..  Infancy failure is the most common problem with these types of electronics.  the fail very early in life if they are going to fail at all.  This is a huge issue for the Chicoms and an area where the brand names have probably invested lots of time, money and research in preventing.   I suggest trying to put lots of hours on you machine early while under warranty.  Think of it like the first few thousand miles on a new car.   break it in and if no problems then I would say the TA you are looking at will be good to go for a long time.   I really like the 252i..   probably what I will get if my Powcon ever dies... which I hope never happens cuz I really like that machine.Tiger Sales:  AHP Distributor    www.tigersalesco.comAHP200x; AHP 160ST; MM350P,  Spoolmatic 30A; Everlast PowerTig 185; Thermal Dynamics 60i plasma.  For Sale:  Cobra Mig 250 w/ Push-pull gun.  Lincoln Wirematic 250
Reply:Originally Posted by RodJHappy August everyone.  ...the general experience is with inverter machines when it comes to reliability ...
Reply:Originally Posted by BradTNAnd you apparently want to trade all that reliability for a Chinese made machine/components with very little track record to determine reliability ?