Miller Syncrowave Contactor?

[malcolm]

I've broken the Syncrowave.

Switched it on this morning and there was a rat-a-tat-tatt noise like a big contactor or relay engaging and disengaging a few times before the machine settled down to normal. It worked a bit but current was down to a dribble, maybe 10% of expected. Tried it on remote contactor and the same thing happened on start up.

It needs a good clean up inside - something I'd been planning to get around to for a while. What does anyone reckon?

Will probably identify the source of the noise when I strip the panels off, though a good tidy up required first so I can get to it.

 

[madkayaker]

doesn't sound good keep us all up to date on the patient

 

[rtbcomp]

Syncro gone the way of parrot

I thought you were referring to your car!

 

[irondarren]

in my opinion dust is a major killer, thats why at xmas the portamig will get the sides taken off and a nice good blasting out with air to remove all the dust. Dust tends to get in everywhere and act as insulation or if its metal grinding dust it can act as a conductor either way its bad news. Give it a good clean out Malcolm and see what happends

 

[shenion]

Clean the rheostat for the current control also while you have it open. That has a considerable current. I use 800-grit sandpaper very lightly. The windings are very delicate. Also slide sndpaper under the wiper and move the control.

 

[madkayaker]

as said could be dust try taking the top of the cont actor if you can and give the innards a good blow out. Maybe with a tin of air dust the compressor might be bit harsh and blow bits out that it shouldn't.

 

[weldequip]

try taking the top of the cont actor if you can and give the innards a good blow out

I wouldn't try that Malc, the thing will be all over the workshop & you'll never get it back together properly...you can try spraying it with some 'Contact Clean',won't do any harm, although I suspect the fault is somewhere else...possibly a Relay sticking on a board.
weldequip

 

[malcolm]

Thanks everyone - it's working again!

I took Darren's advice and gave it a good clean with a vacuum cleaner and paintbrush. I'll blow the remainder out. Wasn't that bad inside apart from the rectifier which looks like it's never had the panel off for cleaning.

I found a length of rusty welding rod that had been shorting between the rectifier and the case which may have accounted for the clicking on start up (was roughly in the same place as the noise - I've circled the arcing marks).

The lack of power might have been dirt in the main current dial. It's only a little rheostat. Knocked it around to 250 amps and I was getting that. Back to 120 and OK again.

I'll post some more photos of the insides later. It has diodes the size of tea cups!

 

[malcolm]

So everyone was right after all. The clicking is from a relay inside a big black box, but only a couple of times under start up, and I suspect the current control rheostat is dirty but I've not measured it yet. Works, but amps are unpredictable.

I took some photos of the Syncrowave while it was apart. It's like a welder only bigger. Tea mug included in some of the photos for scale, and in the first a SIP 130.



The rheostat is a sealed for life 1k ohm device in the top right of the photo. Not like shenion's airco.



Here's the main transformer:



And if that wasn't big enough here's the reactor:



Other bits and pieces are largeish too. A switch:



And the rectifier. In a decent MIG these are normally 150mm wide. This one is about 900mm.



And it has diodes you can get your teeth into:



Finally, folk complain about little fans...



I'll have another fiddle probably next year. Seems to weld OK, just the amp control is difficult to predict.

 

[shenion]

Hmm, lots of parts from my Airco in there.

The clicking is most likely the start circuit. Try turning teh start off and see if it behaves differently.

There should be no contactor, that is SCR controlled so it needs no contactor.

BTW, the potentiometer for the current is not sealed (but it is not a rheostat.) The bottom where the leads come out is usually open and you can usually get contact cleaner in there.

 

[malcolm]

HF start or start current? I have them both off. Also I tried setting the machine to remote contactor and that didn't get rid of the clicking. One thing I noticed is the fan doesn't seem to start to get going until after the clicking has finished, so I'm guessing it might be something that doesn't have enough volts while the transformers, capacitors and fan are filling up. Only happens when the machine is first switched on, and not always and not the same number of clicks every time.

SCR - looked it up: silicon controlled rectifier (electric switch). That would explain why there's not a great click when I start welding.

I'll get hold of some contact cleaner for the potentiometer. That would save swapping it hopefully. PS - my spark gap arrangement is identical to your Airco too.

 

[shenion]

Yes, I meant start current.

Did you try the start current on arc? Makes starting real easy. I usually set it about 1/8th turn higher than the weld current.

Yes, I am tempted to add an SCR to my CP-250 with SCRs and bypass the contactor. One less mechanical thing to fail and i can read the voltage all the time.

May just be better to replace the potentiometer. It is a generic 2 watt 100 ohm available almost anywhere. The only differences are the shaft type (fluted, round, or D shaft.)

 

[malcolm]

I'm not convinced my start current switch works. The manual suggests it should boost the current for 1 second, but it seems to over-ride the current setting for the duration of the weld. Getting on well with arc without it though - no problems with starting or sticking.

My pulse setting doesn't seem to be working at the moment either. I think the poor Syncro is feeling old.

Oddly enough the start current potentiometer is identical to the main one and I'd half thought about swapping them. Though it would be more sensible to just go out and buy one. 1000 ohm on mine.

 

[shenion]

Actually, the start circuit was burned out on my Airco. I beleive it was from nit adjusting the spark gaps.

The start circuit relay runs all the time on mine, the on/off switch is after the relay. Your is much more complicated though (Mine has absolutely no electronics.)

Sounds like the start circuit is not working. Will not be a problem on arc, but may cause problems on TIG as it also controls the HF start when welding DC (HF switch in start mode.)

My current control is 25 ohm, 150 watt. Not something you can find easily

 

[malcolm]

Both continuous HF and HF start work perfectly on mine. Spark gaps are about right and in good condition too. I think everything works apart from pulse and start current dropoff. And the foot pedal remote amps annoyingly, though I suspect that one might be a mechanical fault with one of the wires (not got around to looking at that - I've been tigging using the foot pedal start and the panel amps).

I'm much better at mechanical things than electronic things. Could never get my head around electrics and I'm amazed at what you achieve with your gear. Especially when you build your own.

I've not had my black box of relays open yet, but I'm guessing they are the same as yours. Are they serviceable or replaceable?

 

[shenion]

Heh, the "Black box"

Saw that on mine and said "oooh, the electronics". Opened it up and there are half a dozen open-frame relays. Can easily clean contacts or replace them.

For me, it is all easy. Started auto electronics with guitar amp fixing on the side. That was while I was getting my EE degree. Even designing my own welder was simple. It is a nice change from designing boards with multiple processors and near 500 parts.

Had a look at the Syncrowave schematic. Actually very complicated for its day. Now would be done with a small processor and far less parts If you have a multimeter, I can point you where to look to get the footpedal going and possibly the start.

Now if you were nearby, I could stop by and take a look. I doubt you would want to pay the travel expenses

 

[malcolm]

Excellent, thanks. Next time I go in I might have a little look at the relays and see if any are blackened. That might help get some other things working. (A mechanical view of electronics works sometimes.)

If I get completely stuck I have a very clever electrical friend who lives 50 miles away. Though I was planning to save up favours to have him look at my 25 year old Genrad noise analyser that needs hard disc bearings and a backup that involves weird old fashioned disc formatting involving blocks. Pity he's now bought a decent welder as that had been my main source of outgoing favours. Would have been easier if he had kept his 65 to 85 amp live torch gasless thing that he liked to avoid using.

There are good instructions in the manual for foot pedals - I think they might have been nervous that people would make their own, so instructions for checking them with a volt meter prior to connecting.

 

[malcolm]

Oh dear - no current control at all today. Blew a hole in a bit of 6mm sheet, so possibly it's sitting on max. Time for investigations with the voltmeter and wiring diagram.

 

[Wozzaaah]

Hehe, look closely and you might find Beagle 1 down there .
That's not a good sign at all Malcolm, hopefully it's a fairly straightforward and not too expensive fix .

 

[malcolm]

I'm baffled now. Measured the potentiometer and it seems nice and even across the range from 0 to 750 ohms. Didn't seem dirty at all.

Decided as I had nothing to lose I might as well have a look inside the black box. Attached photos of what I found in there for interest. One of the relays had been arcing a bit so I gave it a very light wipe with 800 grit to get rid of any dirt.

Back together and no current again. Turned the machine off and cycled all the switches and it seems to be working properly at the moment. Probably not for very long though.

Dirty contact somewhere might account for the low amps, but not the mysterious high amps. Still, contact cleaning this afternoon to see if I get lucky.