I have two units of the same flash Canon Speedlite 540EZ. The first one gives the squeal for a few seconds as it charges, an then the sound dies out and it doesn't charge at all. This after a few previous times in the recent weeks when the charging time was longer than usual. The other doesn't even do that - it's totally mute and doesn't charge. I opened the 2nd one, and didn't find any physical issues I was expecting, but I suspect it to be the big capacitor at fault for both of them. I have yet to have a bare view of the big cap on the unit I opened, but it doesn't show any physical symptoms as I expected since the housing it is in is intact and all looks clean.
The cap is **broken link removed**.
Capacitor faults account for probably 70% of my workload, so it's no surprise.
What proportion of those
do show any clear physical symptoms like bulges and leaks, and what proportion look all okay but test fail?
Update:
Tested the caps on the 2nd unit using a Digital Multi Meter using the resistance testing. Test is supposed to answer preliminary questions about the caps - on connecting the test leads if the resistance steadily increases the cap is getting charged from the DMM's battery, and if the increase abruptly halts the electrolyte is not okay, and if it shows continuity or the lack of it, it is understood to be shorted or open respectively.
What I have found is that the 222J(circled in blue) stays constant at 269kΩ (I believe it to be okay?) and the cap circled in orange(the blue cap nearer to the center of the board) stays at a constant of 1.75kΩ which I believe to be not okay. I'll have to desolder it and test it further. The rest of the caps were within expectable behaviour, so I didn't test them further.
View attachment 66031
Update2:
Unit 1 seems to be all okay - testing using a nokia phone charger's 5.7v supply(which reads 5.95v on the DMM) the flash shows to be as per expected functionality. The individual AA cells read near to 1.3-1.35v on the DMM, so I didn't expect them to be a big reason for the flash unit to not charge up.
Unit 2 charges(without anything done on it yet at all
), and the big cap shows 165v DC across its terminals, but doesn't get to the 'full charge' red light indicator - it only stays green to indicate a partial charge ready for one shot. Its xenon tube seems cracked due to use. There is also indication of some burn around one of its ends, and signs of some 'exhaust' spewed around.
The cap above circled in orange has a 2.2kΩ SMD resistor in parallel.