Electronics > Repair
Help with bricked APC UPS SMT1500
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jeffrond:
I know I am replying to an old post, but I just bricked a SMT1000RM2U.
I have three of these and found the "daughter board" if you will.  I found that swapping the dead board with another units good board allowed the UPS to function normally.
Digging around on the internet I found this page. Seeing the posts from AstroAU, I was wondering about the chips and which one is causing the brick.

Do you think it is the 93LC66 chip, or does that just hold model number, serial number and other data?
Do you think it is the STM32F103 chip?  That is the microcontroller.  Could that be in a weird non-running state?

jeffrond:
Another interesting item.  While running LaunchFUW and connected to the bricked UPS with the "good" daughter card installed, it says that I can update the firmware.  This is odd since the most recent firmware is 15.0 and that is what is showing on the UPS when I look at the version.  When I click on "more information", these versions show (1.jpg) UPS 15.0, MCU 11.0, UBL 08.5, MBL 11.0.
Next, I put the daughter card into the good UPS and ran LaunchFUW.  Again, it says to update the firmware. When I click on "more information", these versions show (2.jpg) UPS 15.0, MCU 19.0, UBL 08.5, MBL 19.0.  Notice the MCU and the MBL.  They are different versions.
Do you think the different MCU version has something to do with it?  Is the MCU version speaking to the code that is on the STM32F103 chip or a chip on the main board?  Do these different MCU versions handle the firmware differently?  Meaning can MCU version 19(good UPS) handle the firmware version 15, where MCU version 11(bad UPS) not handle the firmware version 15?
Does anyone have any idea how the MCU and MBL are updated?
Does anyone know what chip the MCU and MBL are located on?
tom_e:
Hi,
I dont beleive the 93LC66 is modified during update (has constants like model number, battery model string).
MCU is probably the firmware for the 8051 which runs the inverter (it is on many other models, the PLCC chip). I know that UBL and UPS are the STM32, UBL being the bootloader, first few kb of flash, UPS being the main firmware (>100kb). It logically follows that MBL is then the bootloader for the MCU (as it always has the same version number), but im not 100% sure.

I find it very interesting that you have different firmware versions being reported for MBL and MCU across the 2 models. I am assuming it is ID 18 as it let you update to 15.0 (all the more recent of those models are ID 18 afaik).

The latest firmware image (SMT18UPS_15-0.enc) doesn't update the other 3 components anyway, for some reason, APC removed 2 of them (it only has UPS so MBL, UBL and MCU wont be updated). If you want to update them, an older version would need to be used which does include them.

I recall updating to an older version which includes MCU 19.0 & UBL 08.5 (the file is significantly larger & the update takes longer). I should still have it, so pm me if you want to try it.

What behaviour is the bad ups (MCU 11) it exhibiting when you turn it on (e.g. lights, beeper) ? I am assuming the serial port works so you can still update the firmware.

Thanks,
Tom.
jeffrond:
The bad UPS with the bad daughter board does nothing.  The backlight of the display comes on, but nothing is shown on the display.  No other lights.  I cannot communicate with it via the serial port.

When I put in the good daughter board, I CAN communicate via serial, and that is when I see the MCU version 11.  I wonder if the MCU version 11 is incompatible with UPS version 15.

Anyhow, if you have the update that includes the MCU version 19, I would be very interested in that.
AstroAU:

--- Quote from: jeffrond on September 26, 2024, 09:58:17 pm ---The bad UPS with the bad daughter board does nothing.  The backlight of the display comes on, but nothing is shown on the display.


--- End quote ---

I had this issue with a daughter board as well and upon further investigation and using a multimeter, I checked the resistance across the supply rails and found it to be a dead short on the board.
I put the meter across the 47UF capacitor (C606) and this read ZERO Ohms and beeped on the continuity tester.
What I found was that the regulator chip (5500) the 8 pin SOP chip next to C612 had died. so we sourced some from the net, replaced it and then the board worked again. This chip takes the 5V supply and generates the 3.3v needed by the STM32.
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