Fixing a broken APEX Classic main unit

theatrus

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A few weeks ago my APEX Classic (it wasn't classic when I bought it!) had failed, in a disastrous way: the system had effectively locked up and did not respond to inputs or control any outputs. Upon further debugging, it was even latching up after rebooting, usually a short while into the boot process.

I swapped it with a spare "Lite" unit I had kicking around from a planted tank (really, how much control do those need anyway?) and at least was back in business for the most part.

If you have ever opened up the unit, you'll know there isn't much there:

- LPC2368 main CPU
- NatSemi Ethernet PHY
- An ATTiny for each of the isolated sensor channels (it uses an optoisolator to communicate unidirectionally)
- Maxim CAN transceiver (AquaBus) (MAX3059)
- Various power supply bits (MC34063 DC/DC)
- Atmel "DataFlash" AT45DB161D SPI flash unit

After dumping the unit in the ultrasonic bath (flux everywhere, also some years of salt splash took out one of the VDM connectors), and probing voltages there wasn't much really going on. The unit would reliably hang after about 30s at boot, and now to the point it wasn't even displaying anything sensible on the remote display unit.

This roughly left two options:
- Main MCU had bit the dust. I don't think Neptune ships the bootloader used for this with their firmware update files, so recovering this part would be a hard.
- The data flash had developed a fault due to years of data logging to it.

I went for option 2: DataFlash was dead in some way. Thankfully replacements are easy to source:

https://www.digikey.com/product-det...gies/AT45DB161E-SSHD-T/1265-1034-1-ND/3847271

I pulled the old DataFlash off the board - a mere 10s with hot air, even easier as Neptune did not use lead-free solder here. I attempted to read-back the unit with a handy TL866A universal programmer, and ended up with valid data for many portions, and was able to successfully blank the chip (erase to FF), however programming in one area of the flash back to 00 was failing. Bingo.

Swap the new part in (which is _smaller_ than the original in width - the wider one is no longer readily available), and... it lives! The smaller width requires some careful alignment to cover the existing old pins.

Location of the DataFlash for those interested:

apex_fix.jpg


Old flash above the board, new one installed. Back to the races.

Notes:

- I removed the battery for this picture (it won't wash well :))
- You need to use the firmware update utility to reload the "web pages" (which are stored here as well)
- Doing this will obviously wipe all settings out.
- I haven't tested Apex Fusion functionality since doing this.
 
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Maggie321

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Was it luck you had the universal programmer? Fate? Or proper planning... I don't think I would have one of those laying around.
 
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theatrus

theatrus

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Was it luck you had the universal programmer? Fate? Or proper planning... I don't think I would have one of those laying around.

If you dabble in random electronics bits they are extremely handy. You could also use an Arduino, Bus pirate, etc.

In this case there was no need to preload the external flash with any data - the APEX firmware self bootstraps.
 

kyleinpdx

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I know this is an old thread, but I just saw it pop up.

Kudos, great job man. This type of thing is what got me into my career (enterprise IT infrastructure), when you know the rules of the game, you can begin to bend them to your outcomes. Its nice having a hot air rework station at home. I used to have a Weller WHA3000 w/ a heated build plate as well for reflowing BGA graphics chips in the mid 2000's.

Did the repair hold up?
 
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theatrus

theatrus

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I know this is an old thread, but I just saw it pop up.

Kudos, great job man. This type of thing is what got me into my career (enterprise IT infrastructure), when you know the rules of the game, you can begin to bend them to your outcomes. Its nice having a hot air rework station at home. I used to have a Weller WHA3000 w/ a heated build plate as well for reflowing BGA graphics chips in the mid 2000's.

Did the repair hold up?

Yup, still running! I expect several more years before salt eats the uncoated boards or the flash wears out again :)
 

BZOFIQ

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Great work, Did you replace the battery while at it?

It's my understanding that hey tend to go bad on old units and not hold time when losing power. Have a LITE brain on the shelf with that exact problem and no time to address.
 
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theatrus

theatrus

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Great work, Did you replace the battery while at it?

It's my understanding that hey tend to go bad on old units and not hold time when losing power. Have a LITE brain on the shelf with that exact problem and no time to address.
Probably not. It literally just acts as a pH for Ca reactor and heater/chiller controller so I wouldn’t notice if the time was very wrong :)
 

JohnP68

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Hi Theatrus, mine was broken too and I followed your instructions.
Works fine now and saved me €450.

Thanks Thanks Thanks

JohnP
Netherlands
 

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