Disassembling Magicshine MJ-876/878 dive light. And a bit MJ-810e.

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EskilJ

Contributor
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Location
Denmark
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100 - 199
I found no disassembly guide for this lamp, so here is one.

My MJ876 lamp stopped reacting at some light levels.
I could make it react using an external magnet, and using the external magnet actually made it Work for a while.

Theory: the magnet is for some reason weakened. Change the magnet.

So here is a disassembly guide:
To remove the battery:
1) Get a 15mm nut. Drill a bit into the threading using a 10mm drill. This Tool will open the battery compartement:
P4124038_small.jpgP4124039_small.jpgP4124040_small.jpgP4124041_small.jpg
So you can see the nice 6*18650 pack, and if you hoped that the charging connector was Water-tight, it isn't.

To get to the switching ring, you don't need to dismount the battery.

To remove the front:
You can't simply unscrew the lamp at the battery indicator. You need to remove the reflector first:

Remove the glass holder ring:
P4124054_small.jpg
You need to make a Tool to unscrew this. I did like this, and it worked fine:
P4124042_small.jpg
After removing the glass, you see the glass o-ring.
You are now at the reflector. unscrew it to get it out.
P4124043_small.jpgP4124045_small.jpg
You can now un-screw the front part of the lamp, threading is in front of the battery indicator.
P4124044_small.jpg
Notice the two green O-rings.
Remove the two green O-rings, and you can slide forward the battery indicator ring:

P4124046_small.jpg
Then remove the switch ring, beware of the spring/ball:
P4124047_small.jpgP4124050_small.jpg
Notice that the LED window is only single or-ring secured - I guess it is OK, as the Water will compress the plastic opposed to the alu. But it needs to be clean!

Now, the magnet is visible. It is a round disc, 5mm diameter and around 1mm thick.
P4124048_small.jpg
It is very visible why it is weak. It is corroded away. This could also explain why some people complain about sand under the ring. The "sand" could be disintegrated magnet.

Disassembling the Electronics:
I didn't disassemble the Electronics this time, to avoid messing with the heat sink paste under the LED. But it is straight-forward, unscrewing the two-hole ring around the LED.

The magnet is easy to pick out and replace. I'll be back when I've got a replacement.

I also have a Magicshine MJ-810e.
The ring is stuck on that one.
I disassembled it - that is very simple, "just" unscrew it behind the magnet ring.
(Writing "just", as I suspect the threading is slightly glued, it needed quite a bit of power)
The Square 4x7x1mm magnet was everywhere.

In general the lamps look fully like western stuff inside, especially the big MJ-87x's. This both applies to mechanical and Electronics/PCB/SMT mounting quality.
But the corrosion protection of the magnets seem to be the weak spot. Rinse the ring well!
 
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The magnet is easy to pick out and replace. I'll be back when I've got a replacement.

I have to come back and thank you louder. This thread got me thinking about two Trustfire TR-J1 lights that died on me when I was swapping out the POS o-rings for some good ones. Sure enough, a simple refrigerator magnet turned them on. The small magnet in the rings must have fallen out and I did not notice it. So, off to the magnet store. (Cut down pieces of the refrigerator magnet are not strong enough.)

Thanks.

You know, it really is a shame. These Chinese made lights are great when they work but their reliability (and service support) problems limits their popularity and their value. And the fixes that should be applied at production are not expensive.
 
EskilJ;70926 Now:
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It is very visible why it is weak. It is corroded away. This could also explain why some people complain about sand under the ring. The "sand" could be disintegrated magnet.

Disassembling the Electronics:
I didn't disassemble the Electronics this time, to avoid messing with the heat sink paste under the LED. But it is straight-forward, unscrewing the two-hole ring around the LED.

The magnet is easy to pick out and replace. I'll be back when I've got a replacement.
Did you find the replacement magnet? If not, this looks like it: 5pcs Round Strong Magnets Disc Neodymium N35 RARE Earth Craft Model 5mm x 1mm | eBay

Or, I have some coming in 4mmX1mm disks if you would like to try that.
 
I have a two year old MJ-810 whose LED had become much dimmer and discolored. Another unit, purchased at the same time, is still running strong. This happened as the torch was often used out of water in hi beam. Although I have unscrewed the front bezel and battery portion, it is unclear how to remove the lamp assembly for replacement. Magicshine has been zero help (as in "no reply"). Where the battery makes contact, I see a couple small holes for a deep set "special tool"(?) that might be used to unscrew, or ??? This may be the "two hole ring" mentioned above, and is near where the magnet switch is located. Any torch mechanics out there? Eventually I will need to find a source for the replacement LED.
 
You are now at the reflector. unscrew it to get...
How on earth did you manage to unscrew the reflector? I am quite worried that I'll break it if I apply too much force, but can't seem to get it lose on my mj-878.
As it may be obvious from my photos the LED is dead and I'd hate to be unable to fix it. Thus, if anyone knows where to buy a replacement LED I'd love to hear about it.
Any and all pointers are very welcome!20180521_232409.jpg 20180521_232414.jpg
 
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SST-90 have them at home best bin 100-104

https://eu.mouser.com/Optoelectroni...usfj?P=1yzt86zZ1yzs654&Keyword=SST-90&FS=True without star pcb

NEW Original Luminus SST-90 high power LED diode chip 30W 6000K/4000K/3000K/Blue | eBay

unscrew reflector - metal sheet size of credit card (check distance between grooves ) stick it between both grooves and ..unscrew it

PS : I would put some sikaflex 291 in groove with hall sensors
Thanks a bunch for your fast and extremely helpfull reply! I'll try that soon
 
[URL='https://www.ebay.com/itm/NEW-Original-Luminus-SST-90-high-power-LED-diode-chip-30W-6000K-4000K-3000K-Blue/263074448716?var=562075087846&hash=item3d4075854c:m:mToqTKBZGtqJto8abq_QCfw':
NEW Original Luminus SST-90 high power LED diode chip 30W 6000K/4000K/3000K/Blue | eBay[/URL]
20180614_000336.jpg
I managed to get to the LED thanks to you. Do you by any chance know what the two tiny yellow wires marked "R0" are for? I assume they connect to a small resistor, but, when following your link above, I can't seem to see the same resistor on the replacement LED...
 
0That is rare but quite useful . Here you connect small SMD thermistor NTC to sense board temperature . If you use that led ''hard'' and you are not so sure if cooling is OK ( projector, headlights ) you can sense that temperature rise and impact on led driver to dimm output current and protect in that way led .

Measure yours with ohm meter at known temperatures 0°C , 50°C , then you find your type

PS: that led is ''30W'' ! ( factory original 3,7V @ 9,0A ) ....cooling is critical that's why yours die.

like:
https://www.digikey.com/en/articles...protect-led-lighting-systems-from-overheating
 
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https://www.shearwater.com/products/swift/

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