What are the torches doing there?
...on the subject where I clumsily begin an infinite series of tripped circuit breakers...
...on the subject where I clumsily begin an infinite series of tripped circuit breakers...
I checked to make sure that there wasn’t any path of electrocution available, just in case the casing went live. Everything was on a glass table top: OK. Plugged in my monitor’s power cable, flicked the switch… and instantly…
Poof. The whole house had a blackout.
My mother was watching the TV so she was like WTF. My sister was using the hair dryer so she had the fright of her life too. But I was the only one bent over and LOL-ing, because I realized that the entire block of my school (where I originally planned to test the unit) would have blacked out from the residual current surge to the earth. And besides, it’s just really funny to hear their varied expressions of “WTF” in the dark (it was night).
Anyway, I found a torch and reset the circuit breaker to restore the electricity. Then Fernando and I spent the next 2 hours trying to repair the problem:
1. The ELCB (earth leakage circuit breaker) was the one which tripped. The row to the left remained OK. Which means that a current ran in the casing. The casing is earthed with 2 wires, sheathed in green, so the slightest current through these wires would trip the household’s electricity supply as a safety mechanism. Basically, this suggests that the problem was with leakage rather than a short circuit.
2. On repeated tries (and blackouts), we figured out that it couldn’t have been a short circuit because if it were true, we would have smelled something burning from how instantaneously the house went out each time. I had plenty of Maglites, so we rigged up a pretty nice array of lights to examine if there was any smoke.
Very useful because you can adjust the focusing action of the Maglite, and the solid aluminium body feels nice to the touch and resists damage. Good stuff.
3. We tried increasing the gap spaces between the circuit boards and the casing as much as possible where we thought it could have leaked, but it was mostly a physical examination since we didn’t have a multimeter on that day. Didn’t work either. Just had a few more blackouts, which were starting to get really funny.
4. Disconnected the earth wires, which is a really dangerous thing to do. And amazingly, it still trips! The leakage went directly to the earth even without the earth wires(??)
But it was getting late anyway, so we didn’t try anything ambitious, especially because we were underequipped (didn’t expect all that hassle). So… the last thing we did was to take a look at the back of the circuit boards. It was difficult trying to remove the under-casing, because it was bent from all the stress and movement.
I learned another use for those closely spaced, thin vents: you could bend the cover back to shape by using a slotted screwdriver, applying some leverage, and repeating this for each vent until the cover was in shape. Proof of concept again, the casing was removed at last. I was close to giving up and using bicycle chain oil to lubricate and remove the casing.
Anyway, we used a focused light on the opposite side and compared the contrast of the permeated light and the color of the circuit board, and found two suspicious zones where it was particularly brown.
Poof. The whole house had a blackout.
My mother was watching the TV so she was like WTF. My sister was using the hair dryer so she had the fright of her life too. But I was the only one bent over and LOL-ing, because I realized that the entire block of my school (where I originally planned to test the unit) would have blacked out from the residual current surge to the earth. And besides, it’s just really funny to hear their varied expressions of “WTF” in the dark (it was night).
Anyway, I found a torch and reset the circuit breaker to restore the electricity. Then Fernando and I spent the next 2 hours trying to repair the problem:
1. The ELCB (earth leakage circuit breaker) was the one which tripped. The row to the left remained OK. Which means that a current ran in the casing. The casing is earthed with 2 wires, sheathed in green, so the slightest current through these wires would trip the household’s electricity supply as a safety mechanism. Basically, this suggests that the problem was with leakage rather than a short circuit.
2. On repeated tries (and blackouts), we figured out that it couldn’t have been a short circuit because if it were true, we would have smelled something burning from how instantaneously the house went out each time. I had plenty of Maglites, so we rigged up a pretty nice array of lights to examine if there was any smoke.
Very useful because you can adjust the focusing action of the Maglite, and the solid aluminium body feels nice to the touch and resists damage. Good stuff.
3. We tried increasing the gap spaces between the circuit boards and the casing as much as possible where we thought it could have leaked, but it was mostly a physical examination since we didn’t have a multimeter on that day. Didn’t work either. Just had a few more blackouts, which were starting to get really funny.
4. Disconnected the earth wires, which is a really dangerous thing to do. And amazingly, it still trips! The leakage went directly to the earth even without the earth wires(??)
But it was getting late anyway, so we didn’t try anything ambitious, especially because we were underequipped (didn’t expect all that hassle). So… the last thing we did was to take a look at the back of the circuit boards. It was difficult trying to remove the under-casing, because it was bent from all the stress and movement.
I learned another use for those closely spaced, thin vents: you could bend the cover back to shape by using a slotted screwdriver, applying some leverage, and repeating this for each vent until the cover was in shape. Proof of concept again, the casing was removed at last. I was close to giving up and using bicycle chain oil to lubricate and remove the casing.
Anyway, we used a focused light on the opposite side and compared the contrast of the permeated light and the color of the circuit board, and found two suspicious zones where it was particularly brown.
Top-left: possible burn; bottom-left: appears to be glue.
...compare with the glue on the transformer coilThe top/left area was more severe. We turned around and saw that the parts responsible for the marks were diodes. Without any other instruments, we could either suspect that these diodes previously burned out and were replaced, or that these diodes simply get very hot during operation: the circuit boards don’t turn that dark even under exposure to the soldering iron!
So, two problems left to solve:
- either the frequency at 50Hz (from the local power grid) is causing some safety mechanism to trip,
- or there is some undetected source of leakage down there that we can’t point out without instruments,
- or both.
I have to credit that it's mostly Fernando's work here. Anyway, it’s a good test that the circuit breaker in my house is working properly. So… I’ll leave the remaining work and updates for post-examination.
Anyway, the side story regarding Fernando… I met him a long time ago while I was cycling. The first words he said to me were, “Wanna race?” – “Yeah, sure.”
So, two problems left to solve:
- either the frequency at 50Hz (from the local power grid) is causing some safety mechanism to trip,
- or there is some undetected source of leakage down there that we can’t point out without instruments,
- or both.
I have to credit that it's mostly Fernando's work here. Anyway, it’s a good test that the circuit breaker in my house is working properly. So… I’ll leave the remaining work and updates for post-examination.
Anyway, the side story regarding Fernando… I met him a long time ago while I was cycling. The first words he said to me were, “Wanna race?” – “Yeah, sure.”
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