Re: Millermatic 175 question

On Wed, 28 Nov 2007 16:50:20 -0800, NoOne N Particular
<twoblues@xxxxxxxxxxx> wrote:



No weld output; wire does not feed; fan
motor continues to run. Check:

-fan Thermostat TP1 open (overheating). Allow fan to run
with gun trigger switch off; thermostat closes when
motor continues to run. unit has cooled (see Section 2-2).

-Secure gun trigger leads (see Section 3-1).

There is a block diagram for the circuit board with
input/output leads labeled (page 29). It sounds like it
might just be a bad gun trigger switch or a problem en route
to the circuit board for same.


I did have the online manual and I went through it AFTER the kid took
the machine home with him. But it sounds to me like the part "fan motor
continues to run" means the fan is running full speed. This fan is
probably not even running at 1/4 speed. It was running so slowly that
we could not hear it until we got our ears down to the rear of the
machine and then it was barely audible. I'm hoping that his next day
off he will bring it back and I can "play" with it more, and then most
likely take it in for service.

Thanks,

Wayne

Having never heard/seen one of these in action before I can
only make some suggestions.

The circuit board schematic is a mystery, sadly Miller
doesn't want to publish that part. It is possible that the
fan motor is designed to ramp-up speed as needed by control
on the circuit board. It may also just hook to the incoming
mains. It is listed in the parts breakdown as 230 volt, so
it may be possible that you aren't getting the full 230
volts to the circuit board. Check that area and make sure
you have 230 volts getting in to the unit (be careful, 230
volts probably won't kill a healthy person, but it ain't no
fun getting zapped) and making it to the PCB. The fan
running at only 1/4 speed kinda points to this area.

If that checks out, make sure the trigger switch on the gun
is actually getting to the PCB too. Just because you can
hear a little clicking noise when you pull it doesn't mean
that it actually makes contact.

If that checks make sure that the thermal protection sensor
coming from the transformer is hooked to the PCB.

If that checks and you want to try messing with it further,
take some GOOD pictures of the PCB and post them someplace
where I/we can look at them. From looking at the block
diagram it (PCB) really doesn't seem to be all that
complicated.

Good luck and let us know how you make out.

--
Leon Fisk
Grand Rapids MI/Zone 5b
Remove no.spam for email
.

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