Originally Posted by
gar
071211-1713 EST USA
andy.f:
Usually most 5 V logic systems will work down to about 4.5 V (a 10% drop). However, I would expect any 5 V system to work at 4.75 V. You have indicated a supply drop of 0.03 V per card and there are apparently 5 cards. So on this average basis you have a drop of 0.15 V, or 4.85 V if you had an unloaded output of 5 V.
If your supply is actually a 25 A at 5 V unit, then I would expect a well designed unit to drop maybe 0.1 V at 25 A, or an internal impedance of 0.004 ohms.
Possibly there is a trimmer adjustment on the supply for voltage.
You do need to make current measurements. For a machine controller 25 A would sound high.
Apparently you found the original power supply to be defective.
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