Invertec V275-S Thermal Shutdown Problem

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Lately I've been having problems with my Invertec V275-S shutting itself off.  About 5 seconds after powering up the machine, the thermal shutdown light pops on and all power is cut.  No welding whatsoever is being done when this happens, so I know I'm not overheating the machine (haven't even gotten close while welding, either).The thermal shutdown light queues me in to a possibility.  In looking at the wiring diagram for this machine, there look to be three thermal sensors which can cut power: output rectifier heat-sink thermostat, switchboard heat-sink thermostat and choke thermostat.  I'm going to dig into this over the weekend and see if I can temporarily jumper the thermostat(s) and regain power.  Anyone ever dug into one of these machines?  There's A LOT packed in there!Any and all additional suggestions or help on this matter would be greatly appreciated.  I want my Invertec back!
Reply:Way too much going on in there.You could have a look around and remove plugs and reseat them.There are a lot of things that could be causing the problem.They are a machine not to mess around with.Take it to someone to look at it for you.
Reply:Originally Posted by BillyThere are a lot of things that could be causing the problem.
Reply:my local airgas does not work on any machines they will recommend a couple of places that do repair same with the other  two LWS in town
Reply:Originally Posted by pisces_0Any suggestions or ideas?From the troubleshooting section of the manual and the wiring diagram I've come up with the input voltage selector switches (set correctly for 220V, single phase) and three temperature thermo-switches.  Now, I've just got to find the thermo-switches in there...LWS is closed today and tomorrow, but we've got both a Praxair and Airgas supplier locally.  I'd assume they'd be able to point me in the right direction or do some work on this machine if need-be.
Reply:Did some digging into the V275-S this afternoon...First, I discharged both capacitors per the manual with a large resistor picked up at the local Radio Shack.  Voltage read zero across the terminals after 15-20 seconds of hooking up the resistor.  From what I've read here and elsewhere, these capacitors can pack quite a punch!Next, on to the three thermo-switches that were in question.All three are N.C. switches and had continuity across the two terminals, so that quick test ruled out an open switch circuit.  I then bypassed all three switches and powered up the machine to verify that they weren't the culprits, and the thermal warning light popped on as it always had and the machine cut power after a few seconds.  Thermo-switches aren't the failure point in this problem so on to the next test.I cycled the power on and off with the main cover removed to see if anything would present itself, and there's a very audible "CLICK" after the thermal warning light comes on.  Power is getting to the P.C. switch board/heat-sink assembly as it should, but a large switch/relay on the board clicks after a few seconds and that's when all power is cut.  At least I now know where the power is getting cut at.  On to more diagnosis as to why and what is causing this switch/relay to trip.Last edited by pisces_0; 11-08-2009 at 04:55 PM.
Reply:Have you tried re-seating all the connectors on the control board? That master relay is being triggered by something that is connected to the sensors, looks like you may have a control board problem, there may be other inputs other than the sensor that is wrong and shutting down the unit.Last edited by transit; 11-08-2009 at 06:51 PM.
Reply:Originally Posted by transitHave you tried re-seating all the connectors on the control board? That master relay is being triggered by something that is connected to the sensors, looks like you may have a control board problem, there may be other inputs other than the sensor that is wrong and shutting down the unit.
Reply:SUCCESS!!I checked and re-seated the voltage selector to auxiliary transformer plug and cleaned and tightened the switch board to main transformer lugs.  One of the lugs on the switch board was a bit loose, so I'm assuming that was the main culprit, but it could have been a combination of these issues.I buttoned everything back up, threw the switch and the machine powered up as normal.  OCV measured 65V across the main terminals and the arc struck beautifully right away.  Fortunately, it wasn't anything major this time, and as a bonus I was able to learn quite a bit about the inner-workings of this machine.Now, back to burning rods....
Reply:Cool. Congrats on the successful troubleshooting. The soldering toys pay for the welding toys.Hakko 928 dual iron, 4xHakko 936Madell 850D Hot Air SMT ReworkMiller 252, HTP Invertig 201 AC/DC, and a Hypertherm 45.