Strange noise from an XMT 304

[Apothecary]

Hello everyone,

Recently, I added a pre/post/spot control to the 22A wire feeder that I have connected to an XMT 304. I tried its functions out to make sure that everything worked, and it was fine. I don't really do much MIG welding (or, compared to most on this forum, much welding at all), so I turned everything off after testing it, and switched the XMT back to stick.

I thought I'd just do a few 7018 beads since it had been quite a few weeks, and everything welded just fine. When I finished and turned off the fume extractor, I expected to hear the cooling fan on the XMT running, but it wasn't. Instead, there was a strange two-part sound: Every 5 seconds or so, it would make a sound that descended in frequency like a falling siren, followed by a higher-pitch beep. I've never heard that from it before.

The 22A was still connected, but I had switched the XMT from remote to panel for the voltage control, and besides, it was set on stick. I haven't removed the 14-pin plug from the XMT, but I never have when stick welding. I'm only including this information in case the pre/post/spot control somehow could cause this, but I don't really see how it could.

Is this some sort of warning sound? There are no help codes displaying on the panel. The fan may not have been running because I really hadn't asked much of the welder--just a couple of MIG beads and three sticks of 7018 at 90 amps, with a good bit of time in between them to look at the results.

I realize that I've only described the sound, and that a recording would be better. If it comes to that, I'll fire it back up and record the sound. However, I didn't want to leave it on any longer than I had to while it was making the noise.

Thanks in advance for any replies.
CW

[Kelvin]

I used one at the community college that used to make a "whistling" sound, but was told that this was common for inverters (never used one before or since)...

[ccawgc]

If you think the fan should have been on, It might have been the fan trying to start up. They make a squeal and a whistle as they start up. Remove the front fan cover and make sure nothing is stuck in the fan, give it a spin by hand and make sure it is not hitting anything. Caution a fan that shorts out can damage the control pcb.
So if fan is clear and moves ok, The next step is to remove the top cover and be ready to test voltage where the fan plugs in to the control pcb on top.
Two pin plug (RC8) on the front left corner of pcb. Caution working on any inverter welder with covers off is dangerous. parts can explode and there are very high voltages present.
If you power up welder with cover off DO NOT STAND ON THE RIGHT SIDE.
stand in front and wear a face shield. Stay back a full arms length. The large capacitors have 330vdc on them. Connect meter to fan plug before turning welder on.
Will read 28vdc after welder heats up and turns fan on. Warning if you run the welder with the cover off and room temp is below 75 degrees the fan will not turn on. Easiest way to turn fan on is to use a heat gun. warm up the temp sensor that is bolted next to the output diodes. A twisted pair of wires that end at a ring lug screwed to the heat sink. You can test the fan by its self if you have a 24 to 28 vdc power supply. Fan should make noise for about 5 seconds as it comes up to speed.
be very careful. get help if you need it. don't want to lose members here.

[Apothecary]

Kelvin,

Thanks for the reply. I've also heard that inverters can make some sounds while operating, something like the sound that a switching power supply can make. (Those are also inverters, so that stands to reason.) I've never heard it from the welder before, however, so that's what is making me a bit concerned. Thanks again!

[Apothecary]

ccawgc,

Thanks for replying. I'll pull the covers, starting with the smaller one, and try the steps that you've outlined. I'm no stranger to electronics and electricity, but through the years the voltages I've worked with have been rather low, such as 5 volts on an IC breadboard, 12 volts in automotive circuitry, and 120/240 volts in household wiring. Some dabbling in building tube guitar amps a few years ago had me running scared of the voltages involved. Suffice it to say that I'll have a healthy respect for the dangers involved, and thanks for pointing them out. I've heard something about those large capacitors before, and don't want to be in the same neighborhood as they are if they were to explode!

If this corrects the problem, I'll post the results here so this will be searchable should someone else have a similar situation in the future.

Thanks again,
CW

[Apothecary]

Good news: With the welder off, I removed the fan cover, and the fan itself was actually stuck. I turned it by hand and it freewheeled one round and stopped again. For some reason, only one or two blades were dragging on one side of the shroud. The shroud had accumulated a bit of dust, but not much, so I don't think that caused it. Once I found which blade was dragging at what spot, I carefully put a little pressure on the fan to bend it away from the spot, and everything spun freely. There probably is a better way to get clearance than by tugging at the fan, but I wanted to quickly see if that made a difference.

When I turned the welder on, the funny noise was not there. I welded a few beads with the same settings as yesterday, with the intent of making the fan run if it would. Once I turned off the fume extractor and the building fan, I listened for the XMT cooling fan. At first, there was no sound, and I began to wonder if some sort of breaker, fuse, or overload relay had been tripped. Then, I heard that falling siren sound once again, and was starting toward the welder to turn it off, when the fan started running. The sound I was hearing yesterday, as ccawgc pointed out, must have been the welder's repeated attempts to start the fan. I had never heard the "startup sound" before, but it was good to hear it only once today!

Thanks again to both Kelvin and ccawgc for the replies.
CW