Dark Spot on LED

Hello everyone. I recently noticed this dark area on one of the led's in my MF01 mini. Do you think it's a damaged dome or just a manufacturing defect? The light functions properly and the beam isn't affected. ( Top left in image ) I tried brushing it very lightly with a small brush, but it doesn't come off. Thanks

Kinda looks like the thermal paste seen elsewhere. Probably that, no?

Try a gentle rub with some isopropyl alcohol.

Thanks Nooner, I’ll give it a try with a cotton swab.

Did the alcohol remove the spot?

I wasn’t able to remove it. I tried alcohol on a Q tip but it wouldn’t budge.
I thought it looked like thermal paste also, but it could be something else.
When the light is fully assembled, and on its lowest output, I can see it easily on the led, through the optic.
It doesn’t appear in the beam however.

Maybe the dome of that led was touched with something hot that melted the silicon a bit. The spot seems to look like white or transparant in which case it could likely live there without trouble (only little light/heat absorption), if it was dark coloured it was a burnt dome waiting to happen.

Thanks Djozz, it does look white or grey colored. I’ll keep an eye on it, and if it get worse I’ll be sure to post a new picture
of it. I appreciate the help.

Sometimes it happens that something is glued to the lens and cannot be removed with a cotton swab or isopropyl. I usually first check under a 10x magnifying glass what it is.
You can try to scratch it with a super thin pin, but you have to be very careful not to damage the led even more.

Just saying.

Don’t do it if you’re not sure of your hands.

From the picture, it looks like solder paste. Saturate a Q-tip with alcohol and let it sit on the spot for a few minutes. It may soften enough to be removed. Dried out solder paste is tough to remove from surfaces. Be careful not to damage the dome!

It looks like the grey gunk that’s also on the PCB.
Maybe possible to peel it off with a pointy but not too sharp knife.

Jerommel, you got it! It is silicone.

Thanks for the suggestions. I’ll give them a try.

Good luck !