Help me figure out what is going on with my shoplights

[Truckdrivingfool]

A few years ago I hung 11 cheap shoplights in my shop and life was great. Then in the time span of a month 10 quit working. I figured cheap lights=cheap caps so I tore into one and found a swollen cap to back my theory and ordered some new caps. The first three went smooth, numbers 4, 5, and 6 weren't resurrected after the capectomy so I started looking harder and found a fuse that was blown on all three. Number 7 I checked the fuse first (was good) and proceeded with the cap replacement to bring it back life. Number 8 - Fuse - good, replaced caps, light still no work, recheck fuse - bad. Took it a step further and jumpered across fuse - Instantly popped newly replaced cap.

New caps installed to the same polarity as the old ones (matches the printing on the board too), so I know that its not that. The pcb in the lights have nice wide traces so I didn't cause any kind of solder bridge. I don't see anything else absolutely/obviously wrong or looking fried.

Is it possible they had a bad day at the cap factory and I got a bunch that are somehow absolutely marked and pinned backwards?

What else would cause the fuse to blow by simply replacing the caps?

 

[davenn]

Is it possible they had a bad day at the cap factory and I got a bunch that are somehow absolutely marked and pinned backwards?

not likely

cheap shoplights

that's more likely the cause ... crappy cheap components


Dave

 

[Truckdrivingfool]

Ya but more to my point why would the replacement of the caps suddenly make the fuse go when even the original crappy ones didn't? Plus more over cause the one I sacrificed with the fuse jumper to instantly pop when I plugged it in?

 

[Arouse1973]

Can you take some nice pictures of the inside of the lights and to include these capacitors, also the new ones you replaced the faulty ones with.
Thanks
Adam

 

[davenn]

Ya but more to my point why would the replacement of the caps suddenly make the fuse go when even the original crappy ones didn't? Plus more over cause the one I sacrificed with the fuse jumper to instantly pop when I plugged it in?

because on that unit there is also another fault

as Adam said ... show pix

 

[Truckdrivingfool]

Originals untouched



New installed



Both side by side




If there's anything else I can picture let me know. Also can anyone tell me where I can these? They are smaller than the 5x20mm that I've been able to find. Best I can read they are 2.5A 125v.

 

[Truckdrivingfool]

I'll add that out of 10 I've done 8 and I'm 4 and 4 on the successful vs unsuccessful. Two I know for sure the fuse blew on the first power up after replacing the caps.

For the they have another fault answer I ask why didn't the fuse blow in the first place when the new caps didn't go until I bypassed the fuse?

 

[shrtrnd]

Sounds a lot like davenn and Arouse1973 are right about cheap components being the problem.
As to your trying to ascertain the cause of the fault, two possibilities come to my mind:
1) The bad caps may have weakened other components in the circuit.
2) Are the plugs polarized? I had a problem once where bulbs burned-out too quickly. I traced the problem
to the wiring of the bulb drivers. I had unpolarized plugs, and some of the bulb drivers had the hot lead going
to components that the neutral lead went to in other lights I had in the same mains circuit. Caused damage.
Good luck in figuring this out.

 

[BitHead]

Anecdotal words... I've seen those caps blow before on circuits like that and I replaced them with '50V higher' caps and all was well - sort of - there was still some electrical noise on my shop AM radio - so I had a closer look and found a 'snubber circuit' - diode, resistor and cap - with a blown diode. The switching-transistor-transformer section was putting spikes on those original caps - which exceeded their ac current or voltage rating - and that's the reason they failed. They were rated OK for a circuit that did not have another failed part on it. So... maybe check the diodes?

 

[Arouse1973]

Can you take a picture of the whole PCB looking down on it. Also a whole picture of the bottom side of the PCB, that would be great.
Cheers
Adam

 

[Truckdrivingfool]

Sorry it took so long to get back to this, the plugs are polarized, here's pics of both sides.



#9 the fuse was blown right from the start, so here's me saying ok ya told me so. Since i have no more test equipment than a multimeter I may just be happy with saving half the lights and bite the bullet on buying new cheap shoplights to cover the rest.

 

[twister]

Usually when acap blows up when you apply power it means the polarity is backwards. I did that once! Very loud!