Electronics > Repair

LIDL bug zapper not working

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Gyro:
I'm still thinking capacitance loss or paralleled resistor failure. Given that there's not much else on the board, I think I'm onto a good bet.

The zap is probably calibrated for flies that can get close enough to see the light! :D


P.S. My wife just reminded me that we have one of those zappers hidden in a corner of the garage. It's a ZER880 (Amazon, <£10). Different design though, a self ballasted cold cathode Edison screw lamp. The zapper gives an almost screwdriver welding spark if shorted! Not a lot of help for your current investigation though, sorry.

soldar:
Yes, this is all turning out to be quite disappointing. No big zaps and sparks and no clear diagnosis of the light not working right.

After testing the caps and resistors of the ballast circuit I am quite certain they are good and the only two things left are the tube and the starter. Of those two I am quite certain it must be the tube. Probably has some odd voltage characteristic, too high or too low or something.

Since I have a magnetic ballast and it works fine with that I think the solution is to just use that.  On the other hand the magnetic ballast probably uses quite a bit more energy than the capacitors.

I am surprised these days they don't just use LEDs and are still using tubes.

wasedadoc:
The starter in the first photo does look suspect to me. There is a huge gap between the moving contact and the lower fixed one. Are they supposed to be like that?

Gyro:
The starter looks pretty normal to me. That whole curved bit is bi-metal so moves a good bit. It also needs to have a breakdown voltage that is higher than a running tube, so the electrodes can't be too close.


--- Quote from: soldar on August 09, 2024, 11:50:57 am ---The current does flow becuse the starter bulb glows but the main tube does not start. The circuit is fed directly from the 230 V mains.

--- End quote ---


--- Quote from: soldar on August 09, 2024, 12:51:11 pm ---I took the starter bulb out of the circuit and started the tube manually. The tube starts but is unstable and I can her faint sparking somewhere. I am now assuming it is the capacitors, one or both, and I should take them out of circuit and test them at mains voltage.

I probably do not have replacements in my junk bin so I cannot just replace them.

--- End quote ---

Sorry to say that still looks like lack of current to me. Not just the starter glowing and not closing, but also the tube looking wrong when it is started manually. I think it's possible for capacitor metallisation to self heal to a resistive state, where it still reads correctly on a DMM but has too high an ESR. This has cropped up several times with motor run capacitors, where they read the right value but just won't run the motor.

Unfortunately there's is no way of bypassing anything. Assuming it's a 6" 4W tube with a voltage drop of maybe 50V, the remaining drop from 230V would take a high wattage resistor (hence the capacitive dropper).


P.S. If you really suspect the starter, you could just pull the guts from an ordinary 2 pin one - the board even has the same anonymous interference suppression cap that you find inside the can. Make sure it's a low wattage one.

soldar:
Definitely not the caps or the resistors or the starter. The starter is not even needed as I can start it manually without the starter. After many experiments and tests I have it quite clear that it is the tube which has different characteristics than it should.

I have tried increasing and decreasing the capacitance of the series caps but it did not help

In any case, using a magnetic ballast it starts and works fine so, for now, that is what I am doing. The two drawbacks are (1) the ballast has to be placed externally and (2) it consumes about 6 W. The device consumes about 4 W when working right and 10 W with magnetic ballast.

If I decide to keep the magnetic ballast I will have to find a way to mount it. Maybe I will keep thinking of further experiments.

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