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If you hunt around the various FPV forums you can find online discussions that complain about defective DJI IOSD-Mini modules. There's a surprising number of installations that have experienced the issue. After a bit of digging I think I have uncovered useful information that points to a likely cause. But first let's define the problem. The failure complaints come in two flavors. 1. DOA, never worked (no video). 2. Worked for awhile then stopped working.

The iOSD Mini modules that are initially reported as DOA often have a happy ending. That is to say, some users with that problem were able to get things going after correcting an installation mistake. So when the module's video is dead from the start I think it would be a very good idea to check for wiring issues and other problems. So get back in there and figure out what you did wrong.

But the iOSD Mini installations where the module was working, then died later on, is what got my attention. The information presented here is based on two iOSD Mini tear downs. Both modules were reported as dead and both had plastic cases that had begun to melt. The general assumption from those that suffered this fate was something inside the module failed and caused the plastic case to melt.

Here's photos of the two modules.

Module 1: It is very difficult to see the melted area on the case, but the noted plastic has begun to warp. The user reported that it had only been powered for a short time on the bench (no flights).

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Module 2: The second module clearly shows the heat damage. It had been used in several flights without issue, then failed (no camera video).

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It is interesting to note that most of the reported failed iOSD Mini modules still had a blinking green status LED. The iOSD Mini's instructions say that the module blinks when it is communicating, but that information seems to be misleading and a bit useless. Especially since the module will still show the green blinking if the NAZA Flight controller is missing. Let me just say that a blinking Green status LED is **normal** and best described as a simple system heartbeat. Just keep in mind that you can have a working or a failed module with a blinking green LED. However, from my investigation the presence of a Red LED or no LED at all, is definitely the sign of a problem.

BTW, some users have reported their working iOSD Mini has a solid green LED but I've never seen that myself. Honestly, the status LED feature is a mess. Until DJI publishes accurate information on the various colors and blinks I think we'll just have to be wary of the LED's usefulness.

So that's the background to the problem. Next: What's going on?

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I was able to get both of these modules in my hands and the detective work began. When I checked them I found Module #1 was indeed bad (no video, but the green LED still blinked). However, Module #2 (with the horribly melted case) worked fine for me. So it is likely that the user's problem was elsewhere and the melted case was merely a distraction. But regardless, the damaged plastic case is indeed a symptom of a problem that needs some attention.

A temperature measurement (via IR gun) found that on a factory fresh new/working iOSD Mini the video IC inside the sealed module was +60F degrees above ambient. Of course the temperature is much cooler with the plastic case removed. The heat is able to rise to the high temperature because the module's plastic case does not provide proper ventilation. It's a tiny Easy-Bake oven.

The Video OSD IC is shown in this photo. It's the component that is creating the excessive heat.

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BTW, the module with the severely melted case was mounted inside a DJI Phantom's plastic shell. So in this installation overall air flow was severely restricted. One important thing to be learned at this point is that the iOSD module needs forced airflow during use. With a smartly chosen mounting location the spinning props will take care of that requirement. If there's not enough air flow then expect the module to eventually look like a melted chocolate candy bar, but without the tasty goodness.

The melted case leads us to a more important issue. It's strong evidence that the high operating temperature is most likely the cause for some of the iOSD Mini failures. I don't expect it is the reason for all of them, but certainly it has shortened the life of some modules.

Next: Can a dead iOSD Mini be repaired?

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I could have just ended the tear down with the knowledge that these modules run hot and need a lot of airflow for longest life. And the failed iOSD was under warranty so it could go back to DJI for exchange. But this is a DiY site -- So let's get out the soldering iron and do a DiY repair to the bad iOSD Mini.

There's no part number on the video OSD IC. But the character set seen on the screen, and the IC package size of the chip, hinted that this hot blooded part was a Maxim MAX7456. Some pin probing with the o-scope found that the chip's pin-out was a good match to Maxim's OSD IC. I happen to have some of them and so this meant that a DiY chip replacement was practical for me to do.

But I have to share that something odd seemed to be going on. The MAX7456 IC is relatively expensive ($13 USD @ 10K pieces) and would not be used in a Chinese made product that sold for $69 USD. So there was a chance that my part number guess was wrong. However a search on the China chip sites found prices at about $3 USD each. So this means that China has copied or cloned Maxim's part. Maybe it was something done under a license agreement or maybe not. The silicon industry vendors warn us about unsanctioned copies due to their reduced reliability; Hopefully the OSD chips used in the module have Maxim's blessing. For sure, my replacement chip will be the real deal.

Before removing the chip I found that the XFB and CLKIN pins were dead. These should have the 27MHz oscillator's frequency on them. For a moment I was thinking that the failure was caused by a bad crystal. But when my scope showed that the SDIN input was being pulled down (severely attenuated) I became more convinced that the OSD chip was the likely culprit.

The old MAX7456 was removed with a hot air rework solder station and the PCB's empty pads were restored to as-new condition. Before proceeding with the chip installation the iOSD was powered up to check the behavior of the status LED. With the OSD chip missing (which simulates a seriously dead chip) I witnessed a solid Red status LED (No green blinking). So I learned that if a iOSD Mini has a solid Red LED then that's one of ways the module reports it has a problem.

A new MAX7456 was soldered in place. On the first power up I saw the Red LED remain on for a couple seconds, go out, followed by the familiar green blinking. This long Red period at power-up only happened one time and has not reoccurred. I suspect that the firmware detected a new OSD chip that needed the character set to be updated and it took a couple seconds to do that.

The new MAX7456 brought the dead iOSD-Mini back to life. My successful DiY repair has voided the warranty, so I might as well go ahead and drill some cooling holes in the plastic oven. So in the end I think this salvaged module will be better than new. :)

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Im about to undertake this repair myself and whilst looking for the Max7456 chip here locally in melbourne, saw this:

FISCHER ELEKTRONIK - ICK SMD A 5 SA - HEAT SINK, FOR SMD, 123°C/W

Its a small heat sink measuring 6x5x5mm.

I am considering mounting it with conductive adhesive to the top of the maxim chip and have the top of it poking through a square hole in the outer casing. The idea being increasing cooling without needing breather holes where dust can enter the casing.

Is this just overkill and a waste of time and effort? Could there be negative affects?

Opinion would be appreciated. Im a novice so don't have a lot of technical reasons to judge the effectiveness of this idea. Just spitballing the idea.

Thanks

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The heatsink is an effective way to help keep the MAX7456 chip cool. I prefer the simplicity of drilling a few holes in the plastic case because cutting the precise opening for the heatsink would be a chore.

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MAX7456 chip replacement

This post has been pretty quiet but I thought Id follow up on my last post on 21 November last year. To recap I had a DJI Mini iOSD that had the dreaded black screen and red flashing light. After reading this post I attempted to try the repair.

It took several weeks for the Maxim chip I ordered from RS in Melbourne to come back into stock but it arrived at christmas. I also asked a friend to buy me a cheap rework station for my birthday in November so by the New Year I was ready to attempt the replacement of the faulty OSD chip on my burnt out DJI mini iOSD.

I was my first effort with tiny SMD's and I found the biggest issue to be seeing what I was doing. This is how it went, for anyone attempting to try this repair:

1. I used the magnifying app on my Galaxy s5 to give me 4x magnification on the work area. Also a bright side lamp to get the right light.

2. Used my 50w soldering iron set at 300 degrees with sharp point tip to desolder each leg of the chip one by one. As they melted almost immediately I bent them up gently to seperate from the board pads.

I was a careless and pushed a bit hard on one, ripping the trace pad from the board. Take your time with this.

3. The chip is attached underneath by solder which I was unable to budge using the rework blower. I had the temp at about 300 deg which may not have been right. I was hestitant to use too much heat for fear of damaging surrounding components. In the end I grabbed the body of the chip with very fine edge side cutters and snapped it off leaving the block of metal which is part of the chip attached to the heat sink pad on the board. I then very easily removed the metal block by touching it with the soldering iron and it came away from the board.

4. Cleaned off the pads and the heatsink pad in the centre of the smd position with braided desoldering wire.

5. Put two strips of liquid solder on the board and a blob under the component to make contact for the heat sink. I put only enough on that it would not squish out when the new Max chip was placed in position. NOTE that when the maxim chip is sitting on even slightly contaminated heatsink pad, the leg dont touch the board. I bent them down very slightly so the chip sat flat and neat with all legs making contact with the board.

6. Then used the rework station to heat the maxim chip for about 20 seconds until all the liquid solder has melted and formed nice clean solder blobs on each leg. The solder will kind of ball up neatly as the flux is burnt off and pulls the chip into position.

7. If you look at the attached pics you will see one very messy pin with a blob of solder on it. That was the position of the trace that I ripped approx 4mm off. Once the chip was in place I carefull laid ONE strand of copper wire onto the leg with the missing pad and melted it to the led with the existing solder. I did this so the copper strand would act as a conduit for solder to bridge the gap to where the trace could be picked up on the board. I just scratch away at the trace until clean copper was exposed. I then put a tiny drop of solder on the tip of the iron and laid it onto the copper wire. It effectively formed a solder extension of the leg.

8. Connected it up to the NAZA, fired up the FPV and sure enough...Nothing..just black screen.

I gave up that day and went to bed.

Next morning with a calm clear head I took another look. Originally the iOSD light was flashed red after it stopped working but since my messy repair the light was now flashing GREEN!

So I figured the chip was being recognised buy the iOSD at least. I checked every pad and found that the one that had been torn off did not look great. I persevered with this contact and put a drop of liquid solder on the board where the wire met the trace.

Tried to fire it up again and ..MAGIC! On screen display in my fatshark goggles.! Very exciting moment.

Light keeps flashing GREEN. Connected the iOSD up to the computer with iOSD assistant. It recognised the iOSD and upgrade it to the latest firmware.

I cut a rectangular hole exactly the same shap as the body of the Max chip with the intention of putting a small heat sink on it which will come flush with the outer casing to hopefully keep this new chip cooler.

I flight tested the unit without the heatsink for about 35 min on ambient temp of 35 degrees and it did not appear to get more than warm to the touch and worked without fault.

Not the prettiest job in the world but will worth the challenge of fixing one's own tiny circuit if you fancy some DIY electronics. Then Maxim was $25. The Yihua rework station with soldering iron was about $70.

Im really a novice at this but reasonably skilled at basic solderwork. Minimum things that you might need to make this work is a very steady hand, a good magnifiying system to see what you are doing (particularly if it doesn't all go smoothly), a good bright work light/area, some cardboard so dont melt the girlfriend's table top, some electrical tape to hold down the iOSD circuit board during the operation, pointy soldering iron, Maxim7456 chip. The rework station with a 5mm nozzle definitely made this job alot easier as the chip is sooo small its quite a challenge to direct a soldering tip under a magnified image of the work. ( for me at least).

If anyone has any criticism of my technique, heat settings etc Id be pleased to have your input. Any tips for future projects are welcomed.

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I personally use a slightly different technique so here are the main differences:

1. I cut the legs off the dead chip right next to the chip body using fine wire cutters and then carefully remove each leg from the pcb using the iron.

2. Clean up the pads.

3. Align the new chip and solder one of the corner legs and check that all the pads are aligned.

4. Solder all the other legs without bothering about solder bridges.

5. Using desolder braid apply to each set of chip legs and run a hot soldering iron the length of the braid to remove excess solder.

I also use a jeweler's loupe to inspect each leg before applying power.

It's very satisfying when it works isn't it?

Peter

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Glad to hear about the success. Regarding the difficulty removing the chip, the 300C degree hot air temp was too low. The PCB has lead free solder plus the MAX chip's bottom bonding pad sucks all the applied heat. I used 400C on several iOSD Mini chip removals and that has worked out fine for me.

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I dont have a hot air tool so cut the legs just the same, less scary too :)

Terry

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The pin cut technique is fantastic for DiY through-hole rework. But something to consider is that this SMD chip has 26mil pin spacing and the traces leading up to it are very delicate. So I expect that some traces might tear off when using the pin cut technique. Also, there is a large soldered bonding pad under the chip that needs to be reflowed during removal (and installation). Although Atwin80d was able to cut his chip apart to break the bonding pad, this technique increases the chance of PCB damage.

That's why the pin cut method on this chip replacement has me nervous. Hot air wands are reasonably priced, so anyone that does SMD soldering or rework should consider adding one to their work bench. After a bit of practice you'll wonder how you lived without it.

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Thanks for the comments..WIth regards to heating the smd enough to melt the heat sink solder underneath, how do you go about applying enough heat without damaging the surrounding close components? When appying the rework heat directly to the top of the chip I was concerned that it was taking too long to absorb enough heat to melt off. I also felt that direct heat was not effectively getting underneath. I also noticed that the heat was melting the clear coating on/around the Maxim chip. Was I being too gentle? Would 400 deg applied though the 5mm nozzle melt it if I had waited a bit longer? I tried a couple of times by grabbing the sides of the chip with sweezers while applying the heat but I couldnt get it to move.

Having just reviewed the Maxim specs it suggests soldering heat to be 300+ deg 10s. Does that mean at least 300 deg for a maximum of 10 seconds? Im not familiar with the lingo..

Is it possible to damage SMD if you have to repeatedly heat them up for soldering?

rgds

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You picked a difficult part for your introduction to SMD rework using a hot air wand. It's a fine pitch IC with a hidden bonding pad (heat sink). Usually a new rework tech would start with some 0603 & 0805 SMD resistors and caps, then progress from there.

When applying the rework heat directly to the top of the chip I was concerned that it was taking too long to absorb enough heat to melt off.

Temperatures that are a bit too low will require unnecessarily long dwell times, so you have to use a temperature that is appropriate for the part. My experience has shown that 400 deg was good for this particular chip removal. But variations in the hot air wand and user technique may require a different temperature. As a rough estimate, I'd say that if the OSD chip has not achieved reflowed within 25 secs then the temp is too low or the technique is wrong.

I don't just point the wand at the top of the chip. I move it around in a circular pattern and evenly heat the pins and component body. I also apply ample liquid solder flux to the pins before removal. The flux will help distribute the heat and promote solder reflow. You'll also need the flux to re-install the new component. The flux is easily cleaned off after the repair using flux removal (sold in a spray can) and an old toothbrush. Spray it on the toothbrush, scrub the area around the newly installed part, then quickly wipe off any excess cleaning liquid with a soft rag.

What's the best temp & dwell time? It all comes with experience and practice. I recommend that you remove some boards out of discarded electronic products and practice on them. You will soon see how different parts need different temperatures and dwell times. Some parts will reflow in five seconds. Others take more time.

Is it possible to damage SMD if you have to repeatedly heat them up for soldering?

In the wrong hands a hot air wand can cause problems. But with a few hours practice anyone can be successful at it. So grab some old boards and pretend you need to repair them. Remove various components, then re-install them. When your rework has a factory made appearance, your training is complete.

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