Is it dead?

[rleete]

Well, the HF micro mill decided it was time to quit. Right in the middle of a project, no less. Thing just stopped. Fault light was on, so I shut it off, turned it back on. Halfway through the cut, same thing. I was able to complete the operation but clicking off and on about 40 times to make two light cuts. Now it won't stay running long enough to spot drill a hole. So much for finishing an engine this weekend.

Ordered the mosfet from LMS, and I'm hoping that's the culprit. If not, I need to either buy a new controller board (over $120 shipped!) or try to figure out a workaround. Since electronics are all greek to me, this is really not going to make me a happy camper.

I'd really like to use this as an excuse to get a larger mill, but the cheapskate in me doesn't want to get all new mill holders, t-nuts, etc. And I can't really justify spending 600 bucks on a mill when I barely hit the limits on this one.


Stay tuned for updates.

 

[Hawkeye]

It sounds to me like the current sensing on the board may have become too sensitive. It likely works by passing the motor current through a low-resistance, high wattage (big) resistor, then reading the voltage across the resistor. If the voltage gets too high, it kicks out the motor and turns on the light.

Open up the case (unplugged, of course) and look for anything that looks burnt. It may be a largish porcelain cylinder with thin wire wrapped around it, then covered in some kind of coating. If that one burns out, the voltage drop across it goes way up, tripping the motor. Also look for any other components that look damaged, especially by heat. See if you can get any info off of the piece - ohms, watts, etc. It might be as simple as replacing it with the same value to get going again.

Look at all the solder connections. Often, a "cold solder joint" is the problem. It can be hard to see. Looks like a VERY fine black or dark circle around the pin where a component is soldered onto the board. A high-powered magnifier is needed. If in doubt, resolder all the connections on the board with an appropriate-sized iron (35 watts or less). The way it quit, this could be your problem. It didn't just die - it failed over a series of tries. Cold solder joints can work fine for years, then start to go.

Good hunting.

Mike

 

[Tony Wells]

Also look closely for any leaking or bulging electrolytic capacitors. Typically, they will be small vertical cylinders with two leads if they are board mounted. Markings will be in μf (microfarads) and volts. They take out more power supplies than just about anything. Easy to replace if you're halfway handy with an iron.