What he said. It's almost always the device that's -48, and the power
supply is usually floating. Floating power supply is fine.
If you turn on the power supply and get out a volt meter you can verify.
You should read the 48V from + to - of course. If you also read 48V
from + to ground (or chassis) then you have a +48V power supply. If you
read 48V from - to ground (or chassis) then you have a -48V supply. If
you don't get significant voltage from either terminal to ground, then
your power supply doesn't care.
The sticker on the PSU should also say either -48VDC, +48VDC, or just
48VDC.
------ Original Message ------
From: "George Skorup" <george.sko...@cbcast.com>
To: af@afmug.com
Sent: 4/19/2017 9:22:31 PM
Subject: Re: [AFMUG] Trango Apex
Most 48v supplies are floating on the output side. I regularly use Mean
Well MDR-100-48's for failed Trango ApexPlus power supplies (which *do*
have the +/0v side tied to the earth side of the AC cord, BTW). The big
capacitor in those usually blow from heat. The MDR works fine with the
+ side going to earth/ground, essentially making a "-48" supply.
I remember that the original Apex power supply was just a brick, but I
don't recall if it had a grounded/3-position AC line cord though.
If you're talking Apex, make sure the supply is at least 1.25A or so.
If ApexPlus, you're going to want at least 1.75A. And obviously you
don't want a supply that ties the negative side to ground.
On 4/19/2017 8:10 PM, Cassidy B. Larson wrote:
I have a trango apex power supply that bit the dust. Says -48v on it.
I don't have a spare -48v. Thoughts on quickest way to restore it to
service? I got plenty of saf ones that show 48v.
