Mag light charger
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Post Fiend
Joined: May 2006
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From: Central Florida
Mag light charger
I tried working it out myself, but I can't make enough sense of it to dope it down. There are two resistors, neither reads what I work them out to be, one should be 87ohm and the other 22ohm. However, they are much higher than that by my meter. The one that should be 87ohm is much larger than the rest of the parts, making me think it's a multiple watt resistor and it's burned the circuit board around it's feet. However I do have some continuity through the LED and the contact point. The diode test out working (both the diode and the LED), but I don't have a way to check the transistor.
Anyone know how to dope this thing down or have a diagram of the circuit?
Anyone know how to dope this thing down or have a diagram of the circuit?
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From: Slimeattle, Weakynton
To properly read resistance and continuity you might have to remove one of the legs of the component to be tested from the circuit, otherwise you might be measuring through other components of the circuit.
The resistor being a resistor, it's possible that it might be burnt out, as the byproduct of current going through it, is heat.
I haven't tested a transistor for a long time, but I remember there were different steps for a PNP and a NPN transistor.
The resistor being a resistor, it's possible that it might be burnt out, as the byproduct of current going through it, is heat.
I haven't tested a transistor for a long time, but I remember there were different steps for a PNP and a NPN transistor.
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Post Fiend
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From: Central Florida
The center leg of the transistor is on the anode of the LED. So I am assuming NPN, but it's been so long since I worked with transistors for me to remember much about them.
Metering across the bigger resistor shows 9.4ohm, the grayish/white stripe is closest to an edge, followed by a violet and brown stripe with a brown stripe on the other side. Resistance could be lower because there is less resistance in parallel to this one, I understand this.
The smaller resistor is blue in color, there is a red stripe closest to the edge, but stripes on the other side are more equally spaced. so the other side goes, Red, yello, black and orange, with the red stripe way on the other side. Resistance is 13.8k ohms.
I'd love to figure it out, but a new charger isn't out of the question.
Metering across the bigger resistor shows 9.4ohm, the grayish/white stripe is closest to an edge, followed by a violet and brown stripe with a brown stripe on the other side. Resistance could be lower because there is less resistance in parallel to this one, I understand this.
The smaller resistor is blue in color, there is a red stripe closest to the edge, but stripes on the other side are more equally spaced. so the other side goes, Red, yello, black and orange, with the red stripe way on the other side. Resistance is 13.8k ohms.
I'd love to figure it out, but a new charger isn't out of the question.
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Post Fiend
Joined: May 2006
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From: Central Florida
Ohm law and such question.
Resistance on the power leads is 12m Ohms. At 12v I would assume 0.001mA. That doesn't seem like enough to do anything, I would have guessed the draw closer to 500mA to 2A. I assume my meter isn't providing enough current and the transistor isn't tripping to give me the load. Could I put say a 10 ohm resistor on the light connectors and try reading voltage drops?
Resistance on the power leads is 12m Ohms. At 12v I would assume 0.001mA. That doesn't seem like enough to do anything, I would have guessed the draw closer to 500mA to 2A. I assume my meter isn't providing enough current and the transistor isn't tripping to give me the load. Could I put say a 10 ohm resistor on the light connectors and try reading voltage drops?
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From: Slimeattle, Weakynton
I'm not familiar enough with this circuit, to be of much help here. I'm assuming it's a 12vdc charger since you haven't mentioned a transformer, capacitors and other stuff.
I'm guessing the depletion state of the battery is what decides the amount of voltage on the base, and therefore how "wide" the gate gets opened, until the battery reaches full charge or high resistance, and the voltage on the base drops and closes the gate, so some kind of resistor on the light charging posts might work.
But, I'm just assuming, and you know what assuming does.
I'm guessing the depletion state of the battery is what decides the amount of voltage on the base, and therefore how "wide" the gate gets opened, until the battery reaches full charge or high resistance, and the voltage on the base drops and closes the gate, so some kind of resistor on the light charging posts might work.
But, I'm just assuming, and you know what assuming does.
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Post Fiend
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From: Central Florida
It is 12v and there is a tiny capacitor connecting the power and ground. I think the light has 3-4 1.5v cells, so it's 6v max. No transformers, just the one cap, two resistors, diode LED and transistor.
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From: Slimeattle, Weakynton
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Post Fiend
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From: Central Florida
I removed the big resistor (one leg) and test both again. All the same readings. However in removing the resistor the transistor fell off. I soldered it back together and but on my battery in the house. I got 12v to the connectors, when I touched them together, the LED lit and the voltage dropped to nill.
I think it was a bad connection. I am going to reassemble it later and test it with the light. I am hoping it works, I bought a new battery for the light only a few months ago.
I think it was a bad connection. I am going to reassemble it later and test it with the light. I am hoping it works, I bought a new battery for the light only a few months ago.
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Post Fiend
Joined: May 2006
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From: Central Florida
I was pretty close then, other than not knowing about 3 significant numbers and forgetting the multiplier.
It's working now. I have it clamped to my battery and the little light is on. If it charges up tonight, I'll reinstall it later.
It's working now. I have it clamped to my battery and the little light is on. If it charges up tonight, I'll reinstall it later.
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