EEVblog Electronics Community Forum
Electronics => Repair => Topic started by: soldar on August 08, 2024, 10:08:28 am
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In LIDL I bought a mosquito zapper Livarno Home 4055334784306. Which did not work when I got home and plugged it in. The box does not say where it was made but it is all designed to give the impression that it is a German product. If you examine the product you have no doubt that it was not made in Germany.
I always keep all my purchase receipts but, as my luck would have it I had lost this one and so at LIDL they would not accept the return without the receipt. Oh well, it was only 10 EUR.
I might attempt to repair it but it might not be worth it.
The light does not work and the zapper does not work either. It flickers a bit and then dies. I seem to remember from the past that they have some kind of capacitor charge pump that raises the voltage for both the lamp and the zapper.
I have not reverse engineered the schematic yet which makes me think this could be a project for BigClive but I have never been able to get in touch with him. If anyone knows how please let me know.
For now I am going to put it aside and I think probably the only thing worth doing is to measure capacitors and test other components. Probably not worth spending much time on this. And if it is the lamp that is bad then better forget it.
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hello,
What type of bulb is this?
Looking at the picture, it looks like the filament does not touch the other pin. Have you tested with the ohmmeter?
Solution if you lost the ticket:
Buy a second one and make the guarantee work for the first. Then resell the second on site ads.
it's " Systeme D"as we say... LOL
cdt
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ooking at the picture, it looks like the filament does not touch the other pin
possibly its the starter for the florry uv tube
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Yes, that's the glow starter for the florescent UV tube. When power is applied, you get a glow discharge in the starter which heats the curved bi-metal strip (not filament), this then bends to touch the other electrode. This completes the circuit through the heaters in the ends of the florescent tube. When the starter cools and opens again, it breaks the heater circuit and the tube hopefully fires (with a discharge voltage drop lower than the glow voltage of the starter.
If the tube doesn't fire then the process repeats, leading to the characteristic florescent tube starting flicker (which has all but disappeared with the advent of electronic ballasts).
P.S. Yes, my guess would be a capacitor lost value or tired tube (or one of the paralleled resistors o/c).
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LIDL would have exchanged it but they were sold out and they would not return the cash I paid.
The glow starter is not of the regular type of glow starter which works in conjunction with an inductance. There is no inductance here and I believe that glow bulb serves a different purpose.
The UV tube has a note saying it is not replaceable and the cables are crimped on. I guess I could disconnect it and test it with a conventional magnetic ballast. I might do it when I decide to dig into this. I think there is a good chance the tube is bad in which case it is better to dump the device.
I think I will just test the caps and other components in the simplest way possible and end there.
Only if I feel very inspired will I reverse engineer the schematic just out of curiosity. I remember I did it years ago for a similar device and it was quite simple with a simple charge pump providing HV for the tube and for the zapper.
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The glow starter is not of the regular type of glow starter which works in conjunction with an inductance. There is no inductance here and I believe that glow bulb serves a different purpose. .
starters dont need an inductor for them to work,there a thermal devices.
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LIDL would have exchanged it but they were sold out and they would not return the cash I paid.
The glow starter is not of the regular type of glow starter which works in conjunction with an inductance. There is no inductance here and I believe that glow bulb serves a different purpose.
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A tube that small doesn't need an inductive ballast to strike, it can be capacitive or even resistive. The starter just needs to bring the heaters (cathodes) up to emissive temperature before opening. Inductor 'kicks' are only needed to strike longer tubes.
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A tube that small doesn't need an inductive ballast to strike, it can be capacitive or even resistive. The starter just needs to bring the heaters (cathodes) up to emissive temperature before opening. Inductor 'kicks' are only needed to strike longer tubes.
Thanks. I was not aware of this. I had only seen them used with inductive ballasts, never with any other type.
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I have tested the tube and starter with a conventional magnetic ballast and they work fine. The tube starts and lights normally so I think it is worth continuing with the repair.
I have disconnected the zapper spiral wires in case it might be a short in that part but no, it makes no difference, it still does not work.
I have measured, in-circuit, the capacitance of the four big capacitors, the three yellow ones and the brown one, and they are all within specs.
I suppose I could test the rest of the components and that would be the quickest.
Or I could reverse engineer the schematic and learn more.
Edit to add: After a cursory check all components seem to be within specs. The two green caps which I am assuming are part of the charge pump are marked 2J473J which I am assuming is 47 nF and they measure about 49 nF. Resistors, diodes, etc all seem to be OK. I guess it is time to reverse engineer.
Another idea: When testing the starter does glow but the tube does not start. The current is flowing through the filaments but the voltage between electrodes is not enough to start. With a regular magnetic ballast it starts but in the zapper circuit it does not start. It seems voltage is insufficient. I wonder if this tube is at the extreme of voltage needs and would work if I feed the device higher voltage .... hold my beer just a moment.... :)
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It looks like the light circuit and the zapper circuit are separate. The light circuit is quite simple as per the diagram. 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.
Maybe I can measure voltage at the tube electrodes and see what the scope shows.
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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.
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I've never had any problem getting my money back on LIDL.
I don't like it / Doesn'¡t work / Whatever.
They only ask you if the product is defective to properly handle it.
First step: Have you checked the solder joints?
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The manager at the LIDL store said she could not process a return paid with cash without the receipt because she needed the bar code. As I said, I always keep the receipts but that one might have fallen out of my pocket or something. She would have exchanged the item without a receipt but they were sold out.
I did inspect all solder points visually and they all looked very good with no defective ones. Still, as they are so few, I did go over most of them.
I have tested the suspect capacitors and they are good. I think it is time to give up.
I might still reverse engineer the complete schematic just for the fun of it.
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I did a quick reverse [whatever] of the schematic. There could be mistakes. What is clear is that there are two completely separate parts. The light circuit and the zapper circuit. Totally separate.
The light does not work. And I think the zapper does not work either. I tried with a tip of a damp tissue and expected it to zap but nothing happened. I suppose I could get more technical measurements.
I don't want to say its crap ... but it's crap.
The light seems to me could be made to work easily by using a magnetic ballast.
The high voltage zapper circuit ... I guess I could find some other circuit that would work better but probably not worth it.
What a waste of time!
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Big Clive reverse engineered one. It seems my unit does the charge pump thing only on one side and the other is just a capacitor and diode.
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Your schematic shows the light and zapper to be independent circuits. No reason why a tube problem would affect the zapper. Not much to be faulty in the zapper. Measure the voltage from the single rectifier side and from the voltage doubler.
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If you bought it for mosquitoes, sadly it doesn't work. Mosquitoes are not attracted to uv light. This thing mostly exterminates little flies and moths.
K.
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If you bought it for mosquitoes, sadly it doesn't work. Mosquitoes are not attracted to uv light. This thing mostly exterminates little flies and moths.
K.
I was just about to say that...
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Your schematic shows the light and zapper to be independent circuits. No reason why a tube problem would affect the zapper. Not much to be faulty in the zapper. Measure the voltage from the single rectifier side and from the voltage doubler.
Yes, light and zapper are totally separate. I have experimented some more and touching the zapper wires with a wet leaf does produce very tiny sparks. I was hoping for a satisfying ZAP! but I guess the tiny spark might be enough to zap the insect.
I guess if I want to increase the zapping power I could increase the value of the capacitors and reduce the value of the series resistor.
In fact, I bought this one to replace an older unit which I assumed was bad but it might be the same thing, that the zapping power is just too small but still there. I still have it and I will have to test it again. The light in that one works fine. Maybe I did not need a new zapper after all.
So the issue remains with the light not working and I am still not clear on where the problem lies. The individual components seems to be OK but they do not work together. In the worst of cases I can just add the magnetic ballast because the light works fine with that one.
I should have left this long ago but, as usually happens, once I get started I can't let go.
I have redone the schematic in order to make it clearer.
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If you bought it for mosquitoes, sadly it doesn't work. Mosquitoes are not attracted to uv light. This thing mostly exterminates little flies and moths.
K.
I was just about to say that...
No problemo. The mosquitoes where I live self-identify as houseflies. ;)
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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.
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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.
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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?
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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.
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.
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.
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.
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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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A magnetic ballast is definitely the way to go. Fluorescent tubes don't do very will with capacitive ballast at mains frequencies. Every time the voltage reaches the tube's striking threshold, a very large current spike flows, through the capacitor, which shortens the life of the tube. An inductor has a high impedance to sudden changes in current, which prevents current spikes.
If you want a more powerful zapper than use larger capacitors and add more stages for a higher voltage and current.
How about ditching the fluorescent tube and replacing it with LEDs? They'll have no problem with a capacitive ballast. You could solder SMT parts in between the tracks of some stripboard.
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At this point the value of all this is anything I learn because these devices cost close to nothing. I need to leave this thing alone because the quality is not good and, for example, the helicoidal zapping wires are aluminum and break easily from flexing.
Magnetic ballasts are better at smoothing current but they consume quite a bit of power and let it off as heat. I guess that is why they also put a resistor in series with the capacitors.
With what I know I feel I might attempt to build a new one or rebuild an old one. The voltage pump is easy and the light can be anything.
In my repairs of different products I am finding quite often a certain incompatibility of components which are technically good and are supposed to be good.
For example, I have USB cables and chargers which are all good but they might not work when coupled in some way so I have sets of cables and chargers assigned to each device and I know they work.
Also with components in devices. Components A and B should work together but they don't. Components A' and B' from a similar device do work. I exchange B with B' and now everything works. It is probably a matter of marginal specs.
I think this is probably the case here. The tube is not bad, the starter is not bad but they just don't work together. Probably a matter of specs being at the limit or outside.
Also, probably the device was tested at the factory and worked well. But maybe now I am using it with different voltage, different temperature (it is extremely hot here), who knows what else may be different.
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You can try to put a wire along the tube, against the glass, connected to one of the electrodes with a 1 Mohm resistor. It can be a thin wire coiled a few turns very spaced. This trick was used in very old fixtures without coil. The resistor is for safety if somebody touches the tube, in your case .. but put anyway
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https://www.youtube.com/watch?v=UP_VLpFnHN8 (https://www.youtube.com/watch?v=UP_VLpFnHN8)
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Yes. That's the exact same one. I wish he would have done it a few weeks earlier as it would have saved me a lot of work.
At any rate, now I have two units stored away waiting for next year's season.