Need help identifying broken component on Zebralight driver

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joebob4501
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Need help identifying broken component on Zebralight driver

I finally got the courage to try and open up my old Zebralight SC600 MK2 to swap the emitter and I successfully removed the bezel without cracking the lens but there was a casualty on the PCB Sad

I was following the thread here: https://budgetlightforum.com/node/62387 about the SC600 MK3, assuming my MK2 would be similar, but the MK2 board had a component that looks to be some sort of inductor that was a lot taller than I expected and the potting material held on to it real good.

It looks like the component was very similar to the big one on the 17mm buck driver MTNelectronics carries here: https://www.mtnelectronics.com/index.php?route=product/product&path=67_1...

Here’s a gallery with some more pictures for those interested: https://imgur.com/a/ynsQ2iV

Edited by: joebob4501 on 02/18/2021 - 15:41
gchart
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Yup, that’s an inductor. But unfortunately I don’t see any markings to be able to tell the inductance value.

joebob4501
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What are the odds the one from the buck driver from MTN will be compatible with the ZL driver? Do you think one with the same size and wire gauge would have the same inductance?

thefreeman
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The H600 II uses a TPS63020, the sc600 II is probably the same, check the markings on the IC next to the defunct inductor pads

The proposed schematics in the datasheet has a 1.5uH inductor for 3.3V at 1.5A, the SC600 probably has a 3.5A output, you can calculate the inductor peak current with the formula page 14, which helps you size the inductance, but… the result will always going to be more than 4A (the switch limit) at low input voltage, so the output will always decrease when the cell voltage is low. Anyway 1.5uH is probably going to be good, it also depends of what you can fit inside the cavity, if you have space for a 2.2uH with proper power rating you can go with that and it would delay a bit the start of the output decrease. (Higher inductance reduce the peak to peak ripple current, allowing the average current to be closer to the switch limit).

In my H600 II (the driver looks identical) the original inductor is 5.15×5.55 with 4.50 height, the cavity is larger (but with round edges),inside could fit, for example, a Xel4030 1.5uH : 8.5A ISAT (30% drop in inductance) and 8.1 IRMS, double of our peak current (4A), that’s good.

By the way the Lume1 driver use the same buckboost IC, with an XGL4020-152MEC (1.5uH).

loneoceans
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This could be the inductor you are looking for:

https://www.digikey.com/en/products/detail/bourns-inc/SDE0604A-1R5M/5030868?s=N4IgTCBcDaIMoBECiAGAbCgLAQQLQEYAlAVgFkQBdAXyA

The important part is to find out what the required inductance is, and if it fits mechanically. As thefreeman said, you may be able to replace the inductor with a physically smaller XEL4030 at 1.5uH (or whichever inductance value it is), as long as it fits in the milled-out cavity. If you can, please try to see if you can make out the markings on the IC (to confirm if it is the TPS63020), and if there are any other markings on the inductor. It would be good if you had better measurements of the size of the inductor if you have a pair of calipers. 

www.loneoceans.com/labs/

- Next-gen Switching Drivers: Lume X1 and Lume1
- High Power Boost Drivers: GXB100 GAN 100W, GXB172 17mm 50W
- Older: GXF22, GFS16, GXB17 & GXB20

joebob4501
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Thank you all for your help!

The IC does appear to be the 63020

I only have cheap plastic calipers without a dial but the dimensions seem to match the one from digikey. The cavity is ~5mm deep and ~6mm in diameter, the broken piece of the original inductor fits with some extra room.

How exactly does the inductance value affect the driver, does it increase output current? Also what is the best way to replace the inductor, hot air reflow and protect the other components with aluminum foil?

loneoceans
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The TPS63020 has a maximum internal switch current limit of 4A (max 4.5A) so this will correspond to the maximum peak current of the inductor, and the minimum saturation current of the inductor (anything >5A will work nicely). It appears that the cavity is quite large, so you should be able to substitute the inductor with anything that will fit. Because the total power is not very high, I would not be too concerned about the need to re-pot the inductor - it floating in the cavity will be fine.

The exact choice of the inductor is a little too complex to discuss over here, but in general, it is a trade-off between higher inductance (and lower ripple current) and cost / size and DCR (where higher inductance values typically have more DCR for a given size). In this case, my guess is that it is unlikely that the feedback loop is too sensitive to the inductance value, and something like 1.0, 1.2 or 1.5uH will work. I would pick something that would have the lowest DCR for the size, to improve overall efficiency (not a big difference but why not). 

It looks like the Coilcraft XEL4030-152ME_ or XEL4030-122ME_ should fit, and is likely to be a small upgrade over the stock inductor (likely lower DCR). But you have to purchase this from www.coilcraft.com directly. You may be able to 'request free samples' and just pay for shipping (or maybe it's free). 

Otherwise, the previous Bourns inductor I linked appears to be a decent replacement as well (you just need to measure the cavity to make sure it fits in both depth, height, and width). 

To replace the inductor, I would use needle tweezers and a regular soldering iron to remove any broken fragments of the old, broken inductor. 

Then I'd de-tin the pads using solderwick. Most likely, ZL uses a lead-free process - lead-free solder doesn't flow as easily and has a higher melting temperature, so it's more difficult to rework. Personally I like Solderwick products for this. Once free of solder, I'd reapply a small amount of leaded solder using a soldering iron so it just covers the pads. Use less solder than you think you need! 

At this point, the best thing to do is to clean the pads with isopropyl alcohol and a small brush to get rid of old flux and residue. Then I typically reapply some flux (I use this, any of them will work well: https://www.chipquik.com/store/index.php?cPath=300), and you can use hot air to reflow the new inductor on.

Note: You may be able to find another inductor with exposed pads, which you can solder directly to the pad with a soldering iron instead using exposed flanges. One example (if it fits) is this: https://www.digikey.com/en/products/detail/vishay-dale/IHLP2020CZER1R5M1...

I wouldn't worry about the other components on board. Just make sure the airflow is not too strong to blow the caps off. The LED and MCU are on the other side so it shouldn't be too much of a problem, but I typically try not to get the hot air too near the MCU (may mess up the flash memory) or the LED (may weaken the silicone dome joint to the substrate). 

The process is the same for your LED swap. It would be nice to see a 4500K 9080CRI Nichia inside, but I'm sure you already have something nice planned. cool

Good luck! 

www.loneoceans.com/labs/

- Next-gen Switching Drivers: Lume X1 and Lume1
- High Power Boost Drivers: GXB100 GAN 100W, GXB172 17mm 50W
- Older: GXF22, GFS16, GXB17 & GXB20

joebob4501
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I just removed the broken inductor pieces and ordered 1 sample of each of the Coilcraft inductors, hopefully one of them will work well! Thank you for the suggestions!

For the emitter I have a XM-L2 4500K 75 cri (XMLBWT-00-0000-000LU20E4) that is said to have a nice tint, and a XM-L2 4000K 80cri (XMLBWT-00-0000-000HT40E5), both from Mouser. I’d like a high cri emitter but it seems finding one in a 5050 footprint is difficult, maybe if Luminus ever releases a SST-40 in high cri I’ll try swapping again.