Mantis illuminator LED failures

Dave did an EVblog on his when he added a brightness adjustment on his.

Mikek

I think so. The wall-wart is 9 volts, but the power passes through the base and comes out 6.3 volts open circuit, 5.3 loaded. Weird. Maybe I'll replace all that.

Or you could just replace them with tungsten, as in my original Mantis. ;)

(Of course I sometimes have to thump it to get the fan bearings rotating right.)

Cheers

Phil Hobbs

Looks like cooling wasn't even a concern to them. Or maybe they didn't really know?

On the weekend I had some time on my hands, courtesy of a major toothache and meds that knocked me out ($525 and a root canal later I am ok). So, I finally cracked open the Radio Shack UHF modulator. The first one had failed within the warranty, this one a while afterwards. And what did I see? A wimpy 78M05 in DPAK and a board that looked like 1/4oz copper, a 1/2" by 1" or so "cooling surface". Totally tanned by now. The solder mask fell off in that area just by turning the board. Couldn't believe it. So now it has a nice big and thick copper chunk and a real T0-220 regulator in there. Still gets to 145F, so you can imagine what that was before. My wife thought that's a miracle so I was rewarded with a nice Trader Joe's Belgian Ale that night. Yummmm.

It always amazes me that some engineers have these really great ideas and the royally screw up the packaging. I think you said it once: 50% of an engineer's job is packaging.

I had just watched that eevblog video a few days ago, There is a LM317 set up as a constant current mode in the arm of the mantis. Maybe that crapped out.

Cheers

Yeah, 50% packaging and another 30% thermal. Circuit design, the fun part, is a few per cent.

Try these:

OK that makes sense. I bet the regulator broke. Its short-circuit current is 1.8 amps, so it fried the LEDs. Bet that didn't cool that very well either.

When you engaged in a start-up a chunk of work also goes into PPT. Doing one right now, not enjoying that.

Oh, Eric the Red's guys are back? Did they vandalize the place and steal all the booze?

Tonight I think we'll have this one, from Spehro's neck of the woods:

Had that after the last election, because "fin du monde" was pretty much summing up the results and we needed some cheering up. Here is the datasheet:

Heat is your enemy. Mount the LEDs on a PCB with fattest(and thickest) possible traces for the leads (especially the one with the chip). Add a little fan and try to modify housing for better airflow. When you are done with the better design, subcontract the making,add the item in your website (maybe similar name?) for competitive sales. "Does your Mantis Illuminator bug you?", "Did the lamps byte the dust?", "our unit will present a cold shoulder to these problems". Summpin like that..

At upwards of $200 a pop, somebody could make beer money fixing bad Mantis LEDs.

Well, it's fixed. It was a serious nuisance.

I replaced the 20 old white LEDs with 12 Crees, and I replaced the 9 volt wall-wart with a Lascar bench power supply. The current limiter in the base is apparently shorted, so I just adjust the Lascar for the brightness that's comfortable. That's 4.8 volts, 80 mA instead of the half-amp before. These Crees are blinding.

Lots of plastic parts, screws, diffusers, mysterious gadgets left over.

After designing my first commercial LED product I was amazed at the brightness these things kick out, versus what I started with 30-some years ago.

That's what made my wife looked skeptical after I fixed the busted evap cooler. Numerous parts were still clattering around on the table next to it and I told her that those are no longer needed.

Runs better than ever before, and more quietly.

If a friend is working on their car and using one of those magnetic dishes to hold the fasteners, try selecting a few random parts from the junk box and discreetly adding them to the mix. ;-)

Best regards, Spehro Pefhany

About a month ago, I left some screws in my pocket, and they came out in the dryer. Horrendous noise, and some had tried to work their way around the seals. Took a quick look on line on how to disassemble a dryer, and took it apart an removed the screws, plus about $1.50 in misc. change! After putting it back together again, it was quieter than it had ever been before, even when new! (We had called out a service man because it was so noisy, and he said that the noise was normal!)

Charlie

When I was a kid, I won a trip to Bell Labs and I saw one of the first LEDs in the world. It was IR, ran in LN2, and was visible through an image intensifier.

Some of the 1" square street-lighting LED arrays look like arc welders at 12 volts/1 amp.

We used to run blue SiC LEDs at 50 mA as panel indicators; now about 2 mA is plenty.

I took ours apart because it was tripping the nat gas combustion chamber overtemperature thermal switch. DIY instructions on the net. Turned it it was clogged with "Spitz" brand sunflower seeds (from pockets of baseball uniforms). Enough of them got past the filter over time. Change gets stuck in the door hinge too.

Best regards, Spehro Pefhany

I still have some of the first generation blue LEDs cree made, from when they started to hand out samples.

they're super super dim by modern standards, but a very pretty sky blue in color. I've not seen any current blue LEDs with the same color, but I'm pretty sure they're no longer using silicon carbide either.

Same goes for old red LEDs. if you dig up some olden days ones with gold plated leads, they're a much deeper red color than most modern ones. Old test equipment has unique color you just don't see anymore. I can't think of any other devices that are old and had LEDs that anybody still has or uses anymore as a comparison.

when was this?

You might want to check thrift stores for old clock radios. Those things often last forever. The only reason we gave our old LED ones away was an international move. They didn't have crystals back then and wouldn't have worked correctly with 60Hz, so we gave them away.

Then old calculators but those displays are tiny and they rarely have individual LEDs.