Some of my previous repairs:
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FixReef is now also on YouTube!
https://www.youtube.com/channel/UCMAmpCr_0gSwhmTNGzXTPtg
Enjoy this repair, now in HD
In my previous repair article I promised another episode about random disconnects and shut offs of the Apex head unit. Many of them have to do with power overload on the AquaBus connection, often caused by several modules connected to it causing damage to the power source.
But this time, we have an even more entertaining case. Out of the left field comes an FMM module. A little $100 addon which could... you guessed it, bring the entire Apex setup down, as it usually happens, while you are on vacation or on a business trip.
The story begins as usual, a fellow reefer sent me their FMM module for repair with an issue that the module causes the 2016 head unit to reboot randomly. Huh? My initial reaction was to suspect the AquaBus communication interface. Perhaps one of the sensor inputs got corroded. What else could a fairly passive module component do to the head unit? But let's not judge the book by its cover. Instead, let's start the investigation.
First, the FMM module was primarily designed to attach various specialized sensors that can report their state back to the head unit. But this module also has a surprise: a single accessory port for aux power, similar to those that are commonly found on an EB832. As we all know, the accessory port provides a controllable 24v power. Since 24v can't come from the 12v AquaBus interface, there is also a 24v power supply input on the module. This story is starting to get much more interesting:
The FMM module is no longer a simple boring passive component. Now it is also a power source. But what does the accessory port power have to do with the head unit shutting down? Oh, we are only getting started.
Next, lets plug in the module as is into a head unit over AquaBus:
As you can see, the module is happily connected and communicating with the head unit over AquaBus. The green LED is on solid. What a happy little module. Or is it?
Next, let's plug it into the 24v power supply. In theory, the 24v power supply will power up the module, it just won't be able to connect to the head unit as there is no AquaBus:
But... to my surprise, there was no blinking green LED and the module appeared pretty much dead. Uh oh, I'm starting to get an idea about what may be wrong here.
It's time to take it apart!
This picture is just such a dead give away (pardon the pun). But wait, the punch line is still ahead.
First, lets go over what we see here. On the lower left is the AquaBus connector. On the lower right is the 24v connector and the accessory port. The big box above is the relay that switches the accessory port on and off. And right above the relay, where my pick is pointing, is the power conversion circuit. It's a 24v to 12v converter, implemented with a buck converter, very similar to the way it's done on an EB832 described earlier.
And by the looks of it, the buck converter, pointed to by my pick is already fried. Indeed it is.
But wait a minute. What is the 12v power conversion doing in a module, which is supposed to provide 24v accessory power?
Well, something has to power the controller and the sensors. Normally, it would be done over AquaBus 12v input, but why not help it with a beefy 24v power supply if available?
Except that, as we learned previously, the power supply capacity matters very little here, because the weak link of the entire 24 to 12v power conversion is the buck converter circuit. The buck converter cannot handle high loads, overheats quickly and either fails permanently or temporary, subsequently cutting power to the entire module.
But the FMM module losing power is not the end of the world, right? True, except for one peculiar detail:
The FMM 24v power input, converted into a 12v power output is routed to AquaBus. That's right! The weak buck converter provides 12v power over AquaBus to other modules. Under normal circumstances this doesn't matter as much, because the EB832 is responsible for powering the AquaBus and any modules connected to it, including the head unit. But what if the EB832 gets disconnected accidentally or fails?
That's right, this tiny little FMM module effectively becomes your primary power source for the entire Apex ecosystem replacing the EB832. Sounds great? Not really. The promised punch line is still ahead!
At this point, the burned color buck converter on the FMM module pictured above kind of makes sense. The unit was never designed to replace the EB832, it was put in the position to do so and it failed due to excessive power draw. So I started by replacing the component using my hot air station:
As I'm heating up the area to remove the buck converter, I noticed transparent liquid starting to come out from under the converter and near by inductor. This was certainly not the flux I was using.
And this is when it suddenly hit me. Let's rewind a little:
Before replacing the buck converter, I had to remove the board from the module case. To do this I had to cut through a thick layer of glue holding the board to the back of the case.
Neptune seems to love using this hot melt glue to hold things together in most of their modules (EB832, DOS, FMM, etc.)
The hot melt glue is just that, it melts into a gooey substance under hot temperature and becomes solid once cools off.
Now let's put it all together. The 24v power is being converted into 12v using a weak buck converter circuit and then routed to the AquaBus port. The higher the power load on the buck converter the hotter it gets. We've seen temperatures north of 158F (70C) on the buck converter under just 350mA load. The buck converter in the FMM module is placed on the board in the corner, right next to where the hot melt glue is applied to hold the board to the case. As the buck converter heats up, so does the board melting the glue and making it flow towards the buck converter. The buck converter is now covered in hot glue, there is now almost no heat dissipation. Finally, the poor buck converter boils itself to a certain death.
This is exactly what we see once the failed buck converter is removed from the board:
First, the burned glue is scraped off from under the converter exposing the melted away and burned top layer of the board as well:
To make matters even worse, the buck converter for this FMM module circuit was used with the lowest possible temperature specs, even worse that that of the EB832:
Oh well... It's now time to fix this mess. As always, the weak buck converter is replaced and upgraded to the highest automotive grade the money can buy:
All of the glue around and under nearby components has also been removed:
And now the 24v power works as expected:
The AquaBus power output produced by the new buck converter is tested under load:
And this FMM module is back into operation once again.
But as always, there is a very important lesson here. By the design decision, which I'm unable to comprehend or justify, this FMM module can be forced to essentially replace the power source of the EB832 and attempt to power all of your Apex modules, including the head unit, display, and many other addons. The module is unable to handle such high loads to begin with, but it also has an even weaker 12v conversion circuit and is held together by hot glue, which melts and further damages heat sensitive components on the board. Thus, I highly recommend using dedicated power on other modules, specifically the head unit. Also avoid any scenarios, where the power to the Apex network can only be provided by the FMM module.
Repairing EB832 AquaBus Power Issues or Why Head Unit Reboots Again
Some of my previous repairs: https://www.reef2reef.com/threads/eb832-attempting-to-communicate-with-apex-bootloader-mode.811958/ https://www.reef2reef.com/threads/another-attempt-at-fixing-apex-eb832.804717/...
www.reef2reef.com
Another attempt at fixing Apex EB832
Some of my previous repairs: https://www.reef2reef.com/threads/radion-xr30-complete-no-light-repair.792711/ https://www.reef2reef.com/threads/radion-lights-board-level-repair.774331/ https://www.reef2reef.com/threads/ai-hydra-fan-connector-repair-significant-corrosion.793402/ First off, let me...
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Apex Display Module Causes Head Unit to Reboot Repair
Some of my previous repairs: https://www.reef2reef.com/threads/eb832-attempting-to-communicate-with-apex-bootloader-mode.811958/ https://www.reef2reef.com/threads/another-attempt-at-fixing-apex-eb832.804717/...
www.reef2reef.com
FixReef is now also on YouTube!
https://www.youtube.com/channel/UCMAmpCr_0gSwhmTNGzXTPtg
Enjoy this repair, now in HD
In my previous repair article I promised another episode about random disconnects and shut offs of the Apex head unit. Many of them have to do with power overload on the AquaBus connection, often caused by several modules connected to it causing damage to the power source.
But this time, we have an even more entertaining case. Out of the left field comes an FMM module. A little $100 addon which could... you guessed it, bring the entire Apex setup down, as it usually happens, while you are on vacation or on a business trip.
The story begins as usual, a fellow reefer sent me their FMM module for repair with an issue that the module causes the 2016 head unit to reboot randomly. Huh? My initial reaction was to suspect the AquaBus communication interface. Perhaps one of the sensor inputs got corroded. What else could a fairly passive module component do to the head unit? But let's not judge the book by its cover. Instead, let's start the investigation.
First, the FMM module was primarily designed to attach various specialized sensors that can report their state back to the head unit. But this module also has a surprise: a single accessory port for aux power, similar to those that are commonly found on an EB832. As we all know, the accessory port provides a controllable 24v power. Since 24v can't come from the 12v AquaBus interface, there is also a 24v power supply input on the module. This story is starting to get much more interesting:
The FMM module is no longer a simple boring passive component. Now it is also a power source. But what does the accessory port power have to do with the head unit shutting down? Oh, we are only getting started.
Next, lets plug in the module as is into a head unit over AquaBus:
As you can see, the module is happily connected and communicating with the head unit over AquaBus. The green LED is on solid. What a happy little module. Or is it?
Next, let's plug it into the 24v power supply. In theory, the 24v power supply will power up the module, it just won't be able to connect to the head unit as there is no AquaBus:
But... to my surprise, there was no blinking green LED and the module appeared pretty much dead. Uh oh, I'm starting to get an idea about what may be wrong here.
It's time to take it apart!
This picture is just such a dead give away (pardon the pun). But wait, the punch line is still ahead.
First, lets go over what we see here. On the lower left is the AquaBus connector. On the lower right is the 24v connector and the accessory port. The big box above is the relay that switches the accessory port on and off. And right above the relay, where my pick is pointing, is the power conversion circuit. It's a 24v to 12v converter, implemented with a buck converter, very similar to the way it's done on an EB832 described earlier.
And by the looks of it, the buck converter, pointed to by my pick is already fried. Indeed it is.
But wait a minute. What is the 12v power conversion doing in a module, which is supposed to provide 24v accessory power?
Well, something has to power the controller and the sensors. Normally, it would be done over AquaBus 12v input, but why not help it with a beefy 24v power supply if available?
Except that, as we learned previously, the power supply capacity matters very little here, because the weak link of the entire 24 to 12v power conversion is the buck converter circuit. The buck converter cannot handle high loads, overheats quickly and either fails permanently or temporary, subsequently cutting power to the entire module.
But the FMM module losing power is not the end of the world, right? True, except for one peculiar detail:
The FMM 24v power input, converted into a 12v power output is routed to AquaBus. That's right! The weak buck converter provides 12v power over AquaBus to other modules. Under normal circumstances this doesn't matter as much, because the EB832 is responsible for powering the AquaBus and any modules connected to it, including the head unit. But what if the EB832 gets disconnected accidentally or fails?
That's right, this tiny little FMM module effectively becomes your primary power source for the entire Apex ecosystem replacing the EB832. Sounds great? Not really. The promised punch line is still ahead!
At this point, the burned color buck converter on the FMM module pictured above kind of makes sense. The unit was never designed to replace the EB832, it was put in the position to do so and it failed due to excessive power draw. So I started by replacing the component using my hot air station:
As I'm heating up the area to remove the buck converter, I noticed transparent liquid starting to come out from under the converter and near by inductor. This was certainly not the flux I was using.
And this is when it suddenly hit me. Let's rewind a little:
Before replacing the buck converter, I had to remove the board from the module case. To do this I had to cut through a thick layer of glue holding the board to the back of the case.
Neptune seems to love using this hot melt glue to hold things together in most of their modules (EB832, DOS, FMM, etc.)
The hot melt glue is just that, it melts into a gooey substance under hot temperature and becomes solid once cools off.
Now let's put it all together. The 24v power is being converted into 12v using a weak buck converter circuit and then routed to the AquaBus port. The higher the power load on the buck converter the hotter it gets. We've seen temperatures north of 158F (70C) on the buck converter under just 350mA load. The buck converter in the FMM module is placed on the board in the corner, right next to where the hot melt glue is applied to hold the board to the case. As the buck converter heats up, so does the board melting the glue and making it flow towards the buck converter. The buck converter is now covered in hot glue, there is now almost no heat dissipation. Finally, the poor buck converter boils itself to a certain death.
This is exactly what we see once the failed buck converter is removed from the board:
First, the burned glue is scraped off from under the converter exposing the melted away and burned top layer of the board as well:
To make matters even worse, the buck converter for this FMM module circuit was used with the lowest possible temperature specs, even worse that that of the EB832:
Oh well... It's now time to fix this mess. As always, the weak buck converter is replaced and upgraded to the highest automotive grade the money can buy:
All of the glue around and under nearby components has also been removed:
And now the 24v power works as expected:
The AquaBus power output produced by the new buck converter is tested under load:
And this FMM module is back into operation once again.
But as always, there is a very important lesson here. By the design decision, which I'm unable to comprehend or justify, this FMM module can be forced to essentially replace the power source of the EB832 and attempt to power all of your Apex modules, including the head unit, display, and many other addons. The module is unable to handle such high loads to begin with, but it also has an even weaker 12v conversion circuit and is held together by hot glue, which melts and further damages heat sensitive components on the board. Thus, I highly recommend using dedicated power on other modules, specifically the head unit. Also avoid any scenarios, where the power to the Apex network can only be provided by the FMM module.
