User Profile

[jjohn76]

I am probably at about a 10% success rate helping troubleshoot board problems, even less with boards I haven't traced to find the schematics. There is usually clear evidence of transistor failure, though the auxiliary power transistors can make a pretty loud bang. If your bridge rectifier is showing...

[jjohn76]

I think I typed too fast up above, and the test points might have been off. Here is what I see as the general circuit, minus the H-bridge inverter snubber network (ran out of room on the right), a possible pre-charge relay/SCR (didn't see these on the board), and RC340A and RC340B might be backwards...

[jjohn76]

Also, check resistance across the large capacitors- positive lead on BUS +, negative lead on BUS Common. There looks to be a connector for the transformer along the bottom of the board, right by the big electrolytics in your picture of the back side of the board. I think the left one goes to the center...

[jjohn76]

Ryan, that seems right. It's a NO relay like TP2 and won't close until the transformer is hot enough. Spending more time looking at the schematic, all 30 leads are connected to the chassis. Any fault in those TPs wouldn't trip the breaker. If you have the motor removed, you should have an open loop...

[jjohn76]

One last thing. I have had the input switch go on XMTs, but they tend to pull much more amperage. I have also seen that switch go in Dynasty 200s, but they were pulling excessive current. When you heard the pop, did the input switch trip? Does it feel much weaker now (easier to switch on/off) or are...

[jjohn76]

Where does the transformer connect to the board? Is there a black plug near the four big electrolytic capacitors at the top?

[jjohn76]

Please make sure you check for voltage across bus common and bus + before working on this. We're already past that in this case, but that will tell you if there is any dangerous voltages in the machine.

You can get an idea on what went bad on that board. Usually, when things go, whatever...

[jjohn76]

If there was a pop, it was likely the input power transistors, which attach to heatsink 5. Can you post pictures? You should be able to see evidence of smoke on the board or cracked transistor module housings on the back side of PC1. I haven't worked on the Maxstar/Dynasty 280s, but they use a boost...

[jjohn76]

Ryan, while you have it apart, it's worth checking if there is a short between the transformer side of TP2 and TP1 and the connector on CB1. The resistance should not be close to zero, but will likely be a single or low double digit number. Because CB1 didn't trip until the machine warmed up (TP1 closes...

[jjohn76]

Here's an example of the crimp connectors from eBay.

https://www.ebay.com/itm/183617977644...

[jjohn76]

I have gone two routes finding these plugs. First route was finding an import plastic plug on ebay. It comes with crimp pins, so you would need the right crimp connectors to do it right. The second route is to search 3106A18-1P on eBay and look for an Amphenol connector. You need to re-clock it, which...

[jjohn76]

Ryan, I have received part specs from Miller Tech plenty of times. It's worth a call. That said, it doesn't seem to me like that was the reason for the CB failing. It's worth doing a resistance check across the leads involved with TP2 and the fan. There is another thermostat, TP1 that's connected to...

[jjohn76]

Ryan, that is probably a good resistance for that motor. My number was a little high and based on some other fans I have. Anything other than open or zero is a good sign. Those thermostats are usually pretty easy to find, a 250V 10A one should do, though you'd have to figure out the right temperature....

[jjohn76]

What are your Tig settings? Have you tried other Tig settings?

[jjohn76]

Ryan, the more times CB1 trips, the less it takes to trip it again. We don't know what caused it to trip before, because it could have been the fan or a previous bad or miswired feeder. It's transferring enough current to close the output relay (small current), but seems to me it's tripping when TP1...

[jjohn76]

Ryan, I don't think the contactor or TP3 are the issue, but if you ever need replacement, it's probably best to match the contactor with another one. It's a 60a three phase contactor with copper E shaped links to run the three contactors in parallel. I replaced one on my CP-300 for much less than the...

[jjohn76]

Ryan, what is the resistance across your fan? TP3 is the second thermostat on your rectifier, in line with your output contactor. What feeder (Spoolmatic?) are you running on it, and I am guessing it is powered through the remote socket? CB1 limits current through your 115V circuit, which is the fan,...

[jjohn76]

Nice!

[jjohn76]

Yeah, I was going to mention Jattus too. Oddly enough, someone posted a Syncrowave pulse unit in ebay. Maybe the seller is reading this post...

[jjohn76]

You would have feeding problems if you just tried to plug the XR-30W into the MM250 because it would be near impossible to match the push and pull motor speeds. There used to be a Push-pull module you could buy for the Millermatic 250 that would let you do this. Sadly, I have only seen one on eBay,...