Miller Aerowave HIGH TEMPERATURE false alarm

I have this Miller Aerowave TIG that I bought at auction.
It does power up, however immediately after powering up it displays a
HIGH TEMPERATURE alarm and does not weld.
Here's what I know:
*) The alarm comes up immediately after powering up
*
) It is cold here (50 degrees F)
*) The display does function and amperage adjustment does change the
display
*
) There are three temperature switches on the machine, one on the
transformer and two on the aluminum heatsinks.
*) All of those switches are electrically "closed"
*
) Serial number is LB028477
*) I checked each temperature switch for continuity and each was
continuous
Would anyone know why a welder like this would display HIGH
TEMPERATURE
when it is not high temperature and all temp switches function
correctly?
Thanks
Reply to
Ignoramus28365
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"Ignoramus28365" wrote in message news: snipped-for-privacy@giganews.com...
Does the continuity extend back to the controller board?
I'd un- and re-plug all the connectors first.
-jsw
Reply to
Jim Wilkins
If it uses a bunch of normally-closed Klixon snap-disk switches as overtemp sensors, they are probably all wired into a supervised loop (alarm if zero current), like a burglar alarm, so a bad connection or cracked wire anywhere will be reported as over temperature.
Joe Gwinn
Reply to
Joe Gwinn
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Possible wires broken inside the insulation in the wiring to the temperature sensor switches?
Possible broken connection in the printed circuit board where the temperature sensor switch wiring connects -- or where it carries the signal.
Possible bad input on a logic chip which is sensing the switches. (Are the three switches connected in series from a reference voltage (possibly ground), through all three switches, and then to logic via a trace in the board? Or is each switch separately wired to the board?
Is it all one big logic bump under epoxy, or are there individual chips scattered around the board? This may determine whether it is easier to replace the board or to replace chips on the board. If individual logic chips -- with part numbers -- you can probably check for the signals to the chips, and out of them, and identify a failed chip, if there is one.
For that matter -- look at the board with magnification for "cold solder" joints. reflow any questionable ones.
Do you have a schematic of the board? If not -- can you get one?
Good Luck, DoN.
Reply to
DoN. Nichols
"Ignoramus28365" wrote in message news: snipped-for-privacy@giganews.com...
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The overtemp switches are on page 29. -jsw
Reply to
Jim Wilkins
Thats a good thought, but not the case. There is continuity in that circuit. Additionally when I short the leads going to it, it does not help.
Reply to
Ignoramus18435
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O.K. The overtemp switches are TP1, TP2, and TP3, so the first thing is to check continuity between RC8-1 and RC82 (wire 62 and 61). If that shows low resistance (e.g. below say 5 Ohms), then it is time to trace the P.C. board, starting at the RC8-1 and RC8-2 terminals.
Of course -- no schematic of the boards. Maybe you can find somewhere where someone traced the boards. If not -- you'll have to do it.
Good Luck, DoN.
Reply to
DoN. Nichols
All I can think of is just the usual electronic debugging stuff:
If the boards aren't encapsulated, look for bad (scorched, or burst cans on electrolytics) or physically damaged caps and resistors. If surface mount , check to be sure the pads and traces haven't been knocked loose in the pr ocess.
Look for conductive debris in the general area.
Look for cold solder joints where the solder has a different "matte" or cry stallized color from the rest and doesn't stick well to the board or compon ent. Check the connectors for damage and make sure they are making good co ntact, both to the wiring and back to the board.
Check for shorted fets and diodes.
In these days of modern lead-free solder, look for tin whiskers shorting be tween solder pads.
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(metallurgy) Whiskers can be physically removed with a stiff brush, heat will also reflo w the solder and the whisker will usually reflow back into the solder pad. If you think it will happen again, add a dab of lead solder when you reflo w.
Of all these, grinding dust or other conductive debris would be my first gu ess.
Sometimes you can spend days tracking down prints and schematics following logic paths to get to the same damaged part you would find with a five minu te visual exam. Extra light and magnification help (a binocular microscope is your friend).
Hope that helps, --Glenn Lyford
Reply to
Glenn Lyford
Hi, I realize this is an old post, but I have the same welder and am having the same issue. Did you ever resolve the problem with your welder? I checked RC8 1 & 2 (specifically I disconnected the plug and checked continuity between wires 61 & 62 inside the plug) I do have continuity there, so I'm suspecting the PC board. Thank you for your time. -Dan
Reply to
Daniel J Vaughan
Hi, I realize this is an old post, but I have the same welder and am having the same issue. Did you ever resolve the problem with your welder? I checked RC8 1 & 2 (specifically I disconnected the plug and checked continuity between wires 61 & 62 inside the plug) I do have continuity there, so I'm suspecting the PC board. Thank you for your time. -Dan
Reply to
Daniel J Vaughan

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