[Titaniumboy]

So my second Meanwell 5V 3Amp power supply arrived earlier today. After swapping out the old one for the new one I get the exact same 10.3 VAC on both of my Harbor Freight multimeters.

Now before you go hating on my HF meters, I already know they are super cheap and nasty. But here’s the thing, they have ALWAYS worked for me and never given me bogus readings before - that I know of. They are cheap enough where I don’t mind if I drop them or loan them out to pesky relatives. One of my HF meters is the free red one and the other is a ten year old Centech clamp on meter.

I am thinking the odds are pretty slim that I received TWO bad power supplies, so I dig up a third non-HF cheapo multimeter that I have. That third meter shows no weird AC voltages.

I am 80% convinced now that both power supplies are actually good and that I am seeing some sort of false readings from the two HF meters. I have a nice Fluke multimeter, but it is now 30-35 years old and needs to be gone through because I can’t trust any of its readings. My BIL has a much newer Fluke, but I won’t be able to get it until tomorrow.

It may be your meter, you mention moving the selector to AC scale. If not auto sensing it may not play well measuring DC on AC setting.

That is an interesting observation. The two HF meters have a 750V and a 200V AC settings that you have to move the selector switch to. The other meter that didn’t pick up the weird AC voltage has a single position for AC Voltage so it must be auto sensing.

I would still put a load on and then remeasure. If you have any power resistors around that have a suitable range try one of those as a load. Do you have access to an oscilloscope?

I will try the resistors if for some reason I don’t get the Fluke meter tomorrow. I’m not willing to risk the UC300ETH quite yet even though I think the odds are 80% or greater that the power supplies are good.

Unfortunately I do not have an oscilloscope. I’ve been looking at some inexpensive scopes for awhile but haven’t pulled the trigger so far. I haven’t used one since college, but it sure would be handy right now.

[Titaniumboy]

I was able to borrow the better multimeter tonight. It ended up being a Klein instead of a Fluke like I thought.

Both power supplies tested out at 0 Volts on the AC scale. Yippee !

The power supper is now feeding the UC300ETH and there is no smoke. Heck, there is even a flashing green light on the UC300ETH board. I’m taking that as a good sign...

Now onto installing the UCCNC software and establishing communication with the UC300ETH. Wish me luck.

[upnorth]

I was able to borrow the better multimeter tonight. It ended up being a Klein instead of a Fluke like I thought.

Both power supplies tested out at 0 Volts on the AC scale. Yippee !

The power supper is now feeding the UC300ETH and there is no smoke. Heck, there is even a flashing green light on the UC300ETH board. I’m taking that as a good sign...

Now onto installing the UCCNC software and establishing communication with the UC300ETH. Wish me luck.

As soon as you mentioned a harbour freight meter I was suspicious of your readings but since you had already decided to try a better meter I said nothing. Glad it worked out for you. Switching power supplies put out a lot of electrical noise so it was probably interfering with your meter. A better quality meter can operate even with the noise.