LED Moving wash failure

[Nicktaylor]

I have had these Chinese units for about three years without any problems. They are being used in a new venue and after all being set up fine on day two they have all started blowing input fuses. We guess something has damaged the power supply and thats blowing the 20mm fuse. We can only imagine an unobserved power surge or similar. Has anyone else come across something like this?

[Stuart91]

If they use discharge light sources, could it be an issue with the power factor correction? I've had this happen on branded equipment as well as generic Chinese units. (Some folks I know got some moving washes which had no PFC fitted, the PCB was marked with a position but the components hadn't been fitted in the factory)

 

See if there are any sickly-looking capacitors inside.

[indyld]

Has anything happened that may have stressed the NTC thermistors that limit inrush? This could be a cause of blown input fuses if there is no other obvious overcurrent reason. Or a surge has done for the MOV. Edited February 20, 2020 by indyld

[bigclive]

Make sure that they're not on an electronically controlled power source (like a dimmer) and check the voltage at one to make sure it's not well off spec if there's a floating neutral. (The voltage would fluctuate with other loads in the same area.)

 

Note that if there is a miswired supply it's wise to treat the whole system as a safety risk.

[Nicktaylor]

Thanks for the ideas chaps. They are LED so I dont think it is a PF issue The next step is how to get into the base to test or replace the PSU. So far we have gone in the top covers but to be honest it rather looks like removing the base plate would make more sense. The power is 16A through a breaker so unless something has happened upstream of that its not repeatable

[indyld]

Depending on the build, taking top base covers and one or both side panels off (screen/ports etc) can often free up the PSU on many models even if it's a squeeze to get out.

 

Usual caveats about 300+v knocking around in a SMPS even when isolated.

 

Edit to add: Meant to say, before struggling to get the PSU out (which let's face it, probably has to come out), just try disconnecting the mains IN to the board and check the L+N for a short. If it turns out that the cable exit gland has shorted out the conductors and the actual PSU is fine, it would be boring to have spent a while trying to get the PSU out.

Edited February 22, 2020 by indyld