Electronic (6v) Lamp failed - troubleshooting

[DaveC426913]

TL;DR

Trying to troubleshoot this little battery-powered lamp that took a bump and stopped working.

Before you start: It's for my granddaughter. I have an obligation to do my due diligence before replacing it with a new one (even if she can't tell the difference).

It took a bump and stopped working.

I've
- replaced the batteries with fresh ones
- disassembled it and (perfunctorily) checked all wire connections (I wiggled them)
- checked for burned out or loose components

I have not applied my multimeter to the problem. I'm only basically electronically savvy. I could check for continuity of battery and wires but beyond that, not so much.

After the wire connections, what is the next most likely component to fail?

Do the filaments themselves fail? I don;t even know what these filamnents are. Ceramic??

BTW, the only thing on the other side of the PCB is the rotary dial.

 

[DaveE]

As you know, it's not really worth repairing if you need to replace parts. It sounds to me like you've checked all the easy stuff. Maybe check the on/off switch and make sure power actually gets to the PCB.

I'm sure there's a bunch of measurements you could make to find out what part is broken, but would it matter? My guess is a broken filament, but I can't really defend it.

What is the label on the IC?

 

[leoherry]

its old tech
the new one must cheaper then the repairing cost

 

[Baluncore]

Do the filaments themselves fail? I don;t even know what these filamnents are. Ceramic??

Those appear to employ "LED filaments".
A long chain of small LEDs are arranged to look like an incandescent filament.

The LED filaments require higher voltage.
The PCB looks like a high voltage linear current regulator.

I would expect the batteries are multiplied up to a hundred volts somehow, before being dropped through the LED chains.

Where is the voltage multiplier hidden?
What is the make and model of the product?

 

[DaveC426913]

Those appear to employ "LED filaments".
A long chain of small LEDs are arranged to look like an incandescent filament.

Right. So they don't appear harsh and cast harsh shadows, I'll bet.

Where is the voltage multiplier hidden?

What does one look like? I didn't notice any components other than the ones I photographed. Not sure where it would hide.

It is powered by 4AA batteries.

What is the make and model of the product?

It's called a LuxPro Retro.

 

[Baluncore]

I didn't notice any components other than the ones I photographed. Not sure where it would hide.

The axial filament construction suggested LED series connection earlier, but maybe the violet LEDs are all in parallel, within each phosphor-loaded silicone-rubber filament. That would run on 6V and not need high voltage.

Low-voltage violet LEDs must be in parallel for 6V, and are all off, so:
1. Check 6V gets to the PCB from battery pack via bent? battery terminals.
2. Check for a cracks in the PCB traces where the supply wires are soldered to the linear regulator PCB.

LED filament introduction, done the live, and careless way.

 

[SredniVashtar]

TL;DR Summary: Trying to troubleshoot this little battery-powered lamp that took a bump and stopped working.

Before you start: It's for my granddaughter. I have an obligation to do my due diligence before replacing it with a new one (even if she can't tell the difference).

It took a bump and stopped working.

I've
- replaced the batteries with fresh ones
- disassembled it and (perfunctorily) checked all wire connections (I wiggled them)
- checked for burned out or loose components

I have not applied my multimeter to the problem. I'm only basically electronically savvy. I could check for continuity of battery and wires but beyond that, not so much.

After the wire connections, what is the next most likely component to fail?

Do the filaments themselves fail? I don;t even know what these filamnents are. Ceramic??

BTW, the only thing on the other side of the PCB is the rotary dial.


View attachment 362843View attachment 362844View attachment 362845View attachment 362846

In your last photo there is a red wire attached to the BAT+ pad, but there is no wire attached to the BAT- wire.

It might be needed.

 

[DaveC426913]

In your last photo there is a red wire attached to the BAT+ pad, but there is no wire attached to the BAT- wire.

It might be needed.

I opened it up to verify.

For some reason, the PCB has two pairs of contacts labeled BAT+ / BAT-.

The ones at the bottom (red/black) are the ones directly connected to the battery pack.
The ones at the top (blue/white/red) are connected to the load.

 

[DaveE]

In your last photo there is a red wire attached to the BAT+ pad, but there is no wire attached to the BAT- wire.

It might be needed.

Or it might not.
Here's a troubleshooting tip. If a device used to work but now doesn't, and it didn't ever have a wire attached to a specific point, you probably can't fix it by adding a wire that never was.

 

[DaveC426913]

Or it might not.
Here's a troubleshooting tip. If a device used to work but now doesn't, and it didn't ever have a wire attached to a specific point, you probably can't fix it by adding a wire that never was.

Sure. But I laud SredniVashtar for his observation and analytical skills nonetheless, for spotting the Bat+ and Bat- pads in that photo, and suggesting I check it out.

 

[rad_controls]

If you haven't already, I would put a meter on the pads that go into the lamp from the PCB and ensure it gets voltage there. If that gets voltage then the problem is most likely with the filaments and its probably not worth it to try and fix.

 

[SredniVashtar]

Or it might not.
Here's a troubleshooting tip. If a device used to work but now doesn't, and it didn't ever have a wire attached to a specific point, you probably can't fix it by adding a wire that never was.

The idea was that a black wire was there, soldering was inappropriate, and it detached from the pad and fell inside the body during disassembly.
I saw the black wire attached to the battery pack but did not see the black wire at the bottom of the PCB.

The op should probe the circuit with a voltmeter. First to see if the battery voltage reaches the pcb, and then to see if there is voltage across the filaments' contacts.
( Be careful, it could be several tens of volts)

Moreover, I would inspect the PCB for missing smd components. It happened to my LED headlamp: fell on the f--- ok I threw it against the wall -- and a transistor and a resistor just came off. Once soldered, it was like new.

 

[DaveE]

The idea was that a black wire was there, soldering was inappropriate, and it detached from the pad and fell inside the body during disassembly.
I saw the black wire attached to the battery pack but did not see the black wire at the bottom of the PCB.

The op should probe the circuit with a voltmeter. First to see if the battery voltage reaches the pcb, and then to see if there is voltage across the filaments' contacts.
( Be careful, it could be several tens of volts)

Moreover, I would inspect the PCB for missing smd components. It happened to my LED headlamp: fell on the f--- ok I threw it against the wall -- and a transistor and a resistor just came off. Once soldered, it was like new.

Yes, our first step in troubleshooting PCBs was always a careful visual inspection. It will be obvious if a wire was supposed to be there. You would also have had a dangling wire, which is an unlikely design feature. Plus, it's in your hand, now's the time to see what else isn't quite right.

Perhaps I made a mistake in assuming that a broken wire would have already been spotted.