[shorton]

I purchased a nice used CNC router from a member here but it came with motors, ready for a G540, but sans electronics. Trivial to add so I ordered my stuff and I ordered a 48VDC 350 watt (7.3A) PS online. A typical mean-well type of switching PS. 48VDC is what the original owner used, so I went with the same. While I waited I hooked up my system to (2) 12VDC batteries in series (I couldn't stand to wait) and got my Geko driver and Mach-3 configured and working. All was good, just needed the real PS to come.

PS finally arrives and I go to install it. Wire it all up and it appears to be dead. Fiddled around with it and in the process blew the fuse in my G540 so I'm down till that arrives. Hopefully nothing else was wrong. Anyway, I'm reasonably electronic savvy and last night I checked and triple checked all my connections and all looked correct. This AM I decided to pull all PS connections except AC and recheck. Sure enough after removing all connections (mainly the ground connection to my Gecko) the power supply came up (mainboard LED came on) and was now apparently working.

I figured out that if the V- terminal was connected to the case (it was with my home and E switches), the PS went back down. It was seen as a short.

The power supply appears to be putting out -48 instead of +48.

With my VOM I check the V- and V+ output terminals, I get +48 between them (common/black attached to the V- side, red lead attached to the V+ side). BUT, if I test between the V+ terminal and the PS case, I get zero VDC. If I check between the V- terminal and the case I get NEGATIVE 48VDC. AC neutral and AC ground are both tied to the case (0 volts between them).

This is wrong isn't it? I think I should see +48 on the V+ terminal (to case), and 0VDC on the V- terminal (to case).

Label on the PS says it's a +48VDC PS. Am I missing something?

I don't see where the company offers a -48VDC PS so has me doubting myself.

[louieatienza]

You should hook the +v and -v of the PSU to the +v and -v of the drive.

[shorton]

Yes, but the problem is V- is -48 relative to (common) ground. I've checked with some other suppliers, their PS all have V- at 0 VDC relaative to case/common ground they say. Either something is wrong with this one, or the outputs are floating and it's a poor design. Inexpensive PS from you know where (AGT S-350 Meanwell copy, apparently).

[LeeWay]

Sounds like a bad supply to me. Lucky if all you blew was a fuse.
I would return that supply and order one from a different source. I have bought the same size from both Keling and CNC Router Parts. The CNCRC supply seems a little nicer quality.

[shorton]

Thanks. I came to the same conclusion.