Author Topic: Astral Pool Robot SMPS exploded - some repair guidance sought  (Read 253 times)

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Offline Lorenzo_1

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Astral Pool Robot SMPS exploded - some repair guidance sought
« on: October 12, 2019, 02:45:58 am »
The control unit for my Astral pool robot expired recently with a loud bang immediately after being connected to power.  Pictures show visible damage on SMPS and microcontroller board.  I’ve annotated the reverse side with the main primary side components and added blue lines where black mask obscures the traces or there’s ambiguity. Some primary side components are hidden by heatsinks.

I’m no expert on SMPS but it looks like this unit uses some of the design elements found in this link - https://datasheet.octopart.com/EVAL6599-400W-T-STMicroelectronics-datasheet-148140.pdf.  It has a sub-board with an L6599AD controller specific to series-resonant half bridge configuration, an L6563 PFC controller and the blown IC turns out to be a Viper12A.  The blown cap was 50V 47uF.  The board outputs 28V to drive the robot and has a 5V three-pin regulator (IC2) supplying the power switch, LED etc (some models have fancier display panel options). Haven’t found a schematic etc for this board.

I have a few questions before I try and repair it:

What is the likely cause? Perhaps indeterminable but might help pin down other components to check.

Do I need to strip components out and clean the board really thoroughly, or will a good was down with circuit board cleaner, IPA etc suffice?

Blown diode D2 is marked A6 and seems likely to be a BAS16. It has an open triangle with T inside as Mfr mark, but I couldn’t tie this down.  Would a BAS16 suit here? R20 looks damaged but reads OK at 1kOhm, consistent with some evaluation circuits I’ve found.

Blown Zener Z2 is unidentifiable but the Viper12A datasheet indicates that Vdd can be between 9 and 38V and switch on/off voltages are typically 14.5V/8V.  Can anyone suggest a suitable replacement value?

Most of the other components appear to have survived. I’ve not tested MosFETs Q2 & Q3, which are 12N50NZs.  Do I need to desolder these to test them out of circuit?  And to what extent would it make sense to desolder other components to clean the board more thoroughly or test them out of circuit? It’s still showing some superficial carbon marks round the blown IC, which won’t come off easily. It’s pretty clean now but not spotless.

Lastly, is this an SMPS that I can start up on a Variac? I have an isolation transformer and lightbulb current limiter I can use with it.  But I understand some SMPS units don’t like low-V startup.

Appreciate any advice members can offer.  Not come across this type of SMPS before and its design and operation appears quite complex.


 

Offline amyk

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Re: Astral Pool Robot SMPS exploded - some repair guidance sought
« Reply #1 on: October 12, 2019, 08:45:36 pm »
What is the likely cause? Perhaps indeterminable but might help pin down other components to check.
Power surge. Those single-chip mains switchers are known to blow relatively often because they're quite sensitive to overvoltage transients.
 

Offline Lorenzo_1

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Re: Astral Pool Robot SMPS exploded - some repair guidance sought
« Reply #2 on: October 23, 2019, 12:57:07 pm »
Thks for the feedback.  I've ordered a 14V zener that I think should do the trick, BAS16 diode, Viper IC and cap.  Will fit them and see whether they're enough to bring it back to life.  Will be a while before I get more time to spend on it.
 


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