24VDC Power Supply Output is 40VDC !!!
24VDC Power Supply Output is 40VDC !!!
(OP)
As my subject header suggest, I have a "regulted" power supply 110VAC in 24VDC out, but measuring the + and - terminals on the output, I am getting 40VDC.
Does this mean that my power supply has gone bad? What could cause this?
Thanks
Does this mean that my power supply has gone bad? What could cause this?
Thanks





RE: 24VDC Power Supply Output is 40VDC !!!
If it does so at rated load, well, it's broken.
RE: 24VDC Power Supply Output is 40VDC !!!
RE: 24VDC Power Supply Output is 40VDC !!!
I confirmed:
Voltage under load: 40VDC
Voltage no load: 44VDC
It's gone bad, and am replacing it already.
However, what kind of safety regulator or switch can I add to the output to make sure that the switch will shut off if it delivers more than let's say 30VDC.
Are there any such safety switches or sensors?
Thanks.
RE: 24VDC Power Supply Output is 40VDC !!!
RE: 24VDC Power Supply Output is 40VDC !!!
RE: 24VDC Power Supply Output is 40VDC !!!
If you have not come across these before, they are usually provided on high current PSUs to overcome any voltage drop in the connecting wires between the power output terminals and the load. The sense terminals allow the PSU's control amplifier to be connected by separate low-current wires so that it can measure the voltage at the point of delivery to the load. It can then adjust the regulator output to compensate for voltage drop as required.
Usually - but not always - the sense terminals are connected locally inside the PSU to their respective power terminals by 100R resistors(+O/P to +S, -O/P to -S). Although this provides a safety feature in case the user forgets, or does not make, either full remote sense connections, or shorting link connections across to the respective power terminals, many older model PSUs did not have the resistors and relied on the user to connect up correctly.
The point of all this is that unless your PSU has a definite fault, the effect you are describing of over-voltage at the output, and no load regulation is exactly the kind of result you can get if the sense circuit is not connected properly.
Worth a check?
RE: 24VDC Power Supply Output is 40VDC !!!
Very true. The Power supply I have is a 7.2A unit, and has +S and -S next the output terminals. However, I can see that the +S and -S are simply wired to their respective output terminals without any resistors.
WOW!
RE: 24VDC Power Supply Output is 40VDC !!!
If you want to try and fix it yourself, if ithe PSU is a simple linear supply, it may be worth checking first to see if one or more of the power transistors on the heatsink has failed short cicuit / or leaky (the most common type is a 2N3055 - they cost a few pence/cents each these days).
Otherwise it will be a case of detailed fault finding.
Good Luck!
RE: 24VDC Power Supply Output is 40VDC !!!
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