BLF GT official support thread [FAQ updated 11 Jan 2018]

NarsilM thinks the voltage is too low.
3 blinks indicate low voltage protection kicks in and the lamp steps back.
But I have no clue about the reason

I ordered the light together with the recommended button top batteries (so directly from Lumintop).

It has been working fine for the last few weeks, last night I saw the issue for the first time and decided to look into it this evening.

Personally I’m not that handy with a soldering iron but I have some colleagues who are; is there a way they can test if the resistor is not functioning properly?

Hmm, that is very strange indeed, particularly if it was working and is not now. That makes even less sense.

First thing I would do is rule out the batteries and carriers. First look over both carriers by eye for any signs of damage, shorts, loose or missing screws. Then try some other cells if you have them. Only use one carrier, try that single carrier in both the front and back position, try the other carrier ect.

See if any combo of cells and carrier makes a difference.

If none of that helps at all, then I think we have ruled out the cells and carrier and the issue must lie in the driver.

Next step would be to pull out the driver, this is pretty simple and you can try getting a good picture of it for us to look at. See if you notice any shorts or missing components.

Do you have the ability to reflash the mcu?

Thanks for your rapid response; I will try everything you mentioned above and report back here with the results.

I have no experience with reflashing an mcu but always can dive into that if needed…

Reflashing the MCU should not be needed, it is just another thing that is reasonably easy to test if you have the flasher.

Do you have a multimeter? That will be needed to test the voltage on the driver if nothing else works.

If you have a multi meter, you can also test the 4 cells when they’re mounted in the carrier and make sure they are around 16+ volts.

Yes, another good test to run.

Ok, I tried the various carrier combinations and that did not help. I also used a multi-meter and both carriers measure 16.99 volts but still the voltage check of the light itself reports 2.2 volts (and I get either 3 flashes and the the light dims or 8 flashes and the light switches off).

I’ll try to open the head, inspect the driver and take some pictures next…

Edit: hmm, tips on how to get to the driver? :slight_smile:

Driver retainer might be loose. Remove battery tube and flip the head over, the large Aluminum ring with 4 holes is the driver retainer. Check if it’s tight. This retainer needs to be removed to get the driver out.

Correct, a pair of small needle nose piers can usually be used to loosen or tighten the ring.

It is strange the carriers are reading 16.99v, with fully charged cells at 4.2V each they should only be reading 16.8v. Could your meter be off? Not a big deal but still odd.

I was able to remove the container and take a look at the board but the wires are pretty short and probably I need to desolder the wires to get the board completely out?

Are there spare driver boards available which might solve the issue?

To remove the driver you have to unsolder the 2 big red and black wires on the led, then unscrew the switch bezel and push the switch pcb through the hole. Then the driver will come out.

You turn the switch pcb sideways and use the notches.

Lumintop is supposed to have some extra drivers available for warranty purposes.

I’ve found that sometimes just loosening the driver and then tighten it back up can sometimes fix things. I think when you loosen the driver retaining ring the driver can slide around. I make sure to center the driver before tightening the ring back up. Thus helps make sure I don’t get a short circuit on any driver components.

For instance, C17 and R6 are pretty close to the drivers edge. If the driver gets shifted to the side, you might short one of those and cause all kinds of issues.

You can also hold a loaded battery carrier directly on the driver so that you know it’s making good contact. Try this and see if it makes a difference.


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Thanks, with your help I was able to get out the driver. I looked at the pcb but don’t see anything weird, missing or damaged.

Is there something I can do myself (or with the hardware dudes at my work) to further ‘test / check’ my driver pcb?

No, just take close up pictures maybe.

You might have corrupt software or a defective component, none of which are visable.

On the other hand, a component might be lacking a little solder or there may be a little too much solder causing a bridge. Which could also cause your issues.

Did you fill out Neal’s form saying you have an issue? Since it seems the driver might be at fault, Neal/Lumintop can probably send you a new driver.

I don’t know exactly how their warranty procedures work.

Maybe add this to the OP or post 2?

Could be handy ;)

Helo TA,

Are there any results / answers from Lumintop to the issues some members had? For example my 3Die LED?

There is one thing you can do, you can check the voltage divider to see if it is outputting the correct voltage but I need to find a good picture of the GT driver so I can point out where that is.

I will try to look for one later when I have more time.

I assume you have filled out the issue survey for the GT already? If not the link is in the OP.

I know of a few issues that have been taken care of so far but it is going much slower then I would like. I am hoping now that the shipments are on hold for a little bit Neal can focus on dealing with the issues.

As long as you have filled out the survey you are on the list of issues I will be tossing at Neal every chance I get until it is dealt with.

Question: what is the URL for the site we put the registered mail tracking number in to see the ETA?

Packageradar seems to be one of the better tracking sites. It’s currently giving me detailed information about every stop of the rail journey that my Lii-500 is making from China…