LaserUser.com Forum (formerly RDWorksLab)

Hi all, I am trying to figure out a mysterous failure on my laser and my air compressor. I have a Ruida 60W red and black laser and a Harbor Freight 3Gal air compressor.

Riddle me this: how could my laser's aux air transistor have killed my air compressor or vice versa when they're not electrically connected?

Yesterday my compressor died (the on/off switch was fried). Today I "hot wired" it by bypassing the switch and it runs fine now. However, now my air assist is running constantly. I measured the voltage going into my relay valve and it's at a constant 24V meaning the aux air / wind pin is stuck connected to ground, meaning the transistor on the controller board is probably fried. I assume this was caused by my solenoid valve drawing too much current. What I don't understand is how could this be connected to the air compressor dying? They aren't electrically connected in any way except that they are on the same power strip.

I suppose there could have been a current spike when the transistor died, but why would that have put too much current through the air compressor? On the other hand if the compressor died first, how would this have generated current to kill the transistor?

I am at a loss, please help me solve this mystery!
-Izzy

The only way I could contrive that the laser caused the failure of the air compressor is if the air assist failed on and discharged the air so that the compressor ran constantly until it failed

Yeah but the compressor runs so much anyway that I don't think it would make much difference. I didn't leave it running overnight or anything, I turn off the main power strip at the end of the day.

The only other thing I can think of was that it was a power surge that made it through the power strip and fried both of them.

dead output transistor can reasonably easily be replaced if you have soldering skills!
I killed the output transistor when I added a valve that consumed too much power. replace with higher rating MOSFET and aback emf diode (I think - not sure one is fitted on the original output)

Thanks! Which specific transistor died on your board? Is it labeled/numbered? I have the RX001-ACC-A motherboard. Looking at it I don't see any dead components but often dead transistors don't show any visible signs. My aux air is stuck on (so there is a constant 24V between the +24V pin and the aux air pin) so it's basically just acting as a ground pin now.

OK I think I have found the culprit! The tiny little transistor connected to the aux air pin has a short between the collector and emitter pins, and is measuring only 20 ohms. It's part number 1P and labeled Q3 on my board. Looks like its the same part as MMBT2222 so I bought a few of those. I might also look for something with a higher max power, and I'm also considering adding a diode between the air pin and the relay valve to isolate them in case that's what killed it