The Bang Test.

telectrix · Sep 22, 2015

Sometimes it's the only way.

let me explain. called out to a MCB tripping when lights ( 9 LED GU10s ) switched on. installation was done by myself 4 years ago. IR test L-N @ 250V read >999Meg. removed 4 lamps, switched on OK. replaced 2, OK. 3rd one in and POP. tripped. QED.

uksparks · Sep 22, 2015

Does it matter which three lamps you put in or is it always the last lamp holder? So can you put them in a different order and its ok until the last one?

telectrix · Sep 22, 2015

it was 1 particular lamp.

uksparks · Sep 22, 2015

So its just one particular lamp holder causing you a problem? is that correct?

Lucien Nunes · Sep 22, 2015

Sometimes it's the only way.

Maybe not. In electronic benchwork the bang test can have expensive knock-on effects. E.g. if a dead high-power amplifier or SMPSU has eaten all its power transistors, the next time you run it up after changing them, if you didn't completely clear the underlying fault it will just eat the new ones in milliseconds, wasting £100s and hours of work.

The trick is to connect a GLS lamp in series as an automatic ballast. Choose a lamp wattage that will not light under normal conditions, so its resistance remains low leaving most of the 230V across the load under test. But if the consumption is much too high the lamp heats up, its resistance shoots up and throttles the supply to the faulty device usually before anything more goes wrong. It also give a very responsive indication of the load that you can monitor the situation with. The same concept is used in PTC 'solid state fuses' but the lamp is faster and more flexible for testing purposes.

A 100W GLS lamp in series with your LEDs would have remained dark when testing the good ones but lit up harmlessly when the faulty lamp was inserted.

telectrix · Sep 22, 2015

uksparks said:
So its just one particular lamp holder causing you a problem? is that correct?

no. faulty GU10.

Deleted member 9648 · Sep 22, 2015

telectrix said:
Sometimes it's the only way.

let me explain. called out to a MCB tripping when lights ( 9 LED GU10s ) switched on. installation was done by myself 4 years ago. IR test L-N @ 250V read >999Meg. removed 4 lamps, switched on OK. replaced 2, OK. 3rd one in and POP. tripped. QED.

Had exactly the same issue at a place a couple of weeks ago,a faulty GU10 LED was blowing the mcb and had trashed a dimmer. Link switch wires...insert a lamp....breaker on,no bang....breaker off,insert lamp,breaker on.....continue like that till it goes bang,replace faulty lamp....new dimmer....home and beer.