Power supply and LED driver technical advice

Reverse Polarity Protection on MEAN WELL DC to DC Converters

12 October 2020

We were contacted by a customer, who had purchased a MEAN WELL SD-500L-24 DC to DC converter. 


They had accidentally applied 24V to it in reverse polarity. 
They replaced the ceramic fuse inside. 

After doing this they found that when they measured resistance across the input terminals, they got <0.1ohms.  
Obviously, the converter would blow more fuses if power was applied again. 
They asked us to suggest anything obvious that they should check next. 

There is a diode across the input after the fuse. This had most likely short circuited. To verify this, you lift one end out and see if it is shorted. It can be replaced with a similar diode available from most electronic component suppliers. It is a 600V, 3A diode. 

Only qualified technicians should attempt to repair a power supply!  

We carry out both in-warranty and out of warranty repairs in our workshop. For further information contact Power Supplies Australia on 1800 632 693.