Fried component U19 - Replacement viability?

[griffinboyle]

Hello,

Yesterday I made the unfortunate mistake of wiping an aluminum chip off of a desk surface, after which it proceeded to land directly on the Kogna and release a plume of magic smoke (I think near JP4/JP6, but I only discovered the aluminum chip after unmounting the damaged board so it may well have moved from the original problem location). Closer inspection seems to reveal that U19 was the only damaged component, so I figured it might be worth a try swapping in a new part.

Thus my question is two-fold: What is the part number for component U19, and are there any upstream/downstream systems which may also have been damaged while/after U19 fried?

Thanks,
Griffin Boyle

[TomKerekes]

Hi Griffin,

Sorry to hear that. U19 is a SN74LVC1G11DBVR 3 input AND gate having to do with resets so unfortunately connects to a few devices including the DSP and Ethernet Transceiver.

Reset.png (9.79 KiB) Viewed 80 times

Good luck.

[griffinboyle]

Hi Tom,

I've just replaced U19 on the fried board. When 5V is supplied it draws ~850mA, and on power-up the two LEDs alternate blinking and then go solid as they should. However, even after booting, it continues to draw ~850mA, and U26 (which I assume is the Ethernet PHY) fairly hot over the next few seconds.

The board is not recognized by KMotion over Ethernet, and Windows Control Panel indicates that "Network Cable is Unplugged" while connected to the Kogna.

When I open the serial COM port over the USB connection, I am seemingly able to establish a connection. However, on startup it just prints "▒▒]"SL▒9q▒Q" and it does not appear to respond to user input.

In your personal opinion does this sound like I just need to re-flash the firmware, or do you suspect that this is a more systemic hardware issue such a the PHY being damaged? Furthermore, if you have any diagnostic recommendations I'm all ears.

Best,
Griffin Boyle

[TomKerekes]

Hi Griffin,

For the LEDs to flash means that a lot of the board is working. DSP, FPGA, Flash, DRAM.

Hard to say what else might be bad.

The Ethernet Transceiver is a:
LAN8741A-EN

Are you sure you have the baud rate set on your Terminal program to 115200?

[griffinboyle]

Hi Tom,

Thanks for getting back to me. You were right to question the baud rate, I had mistakenly set it to 9600 instead of 115200. After changing to 115200 baud I get this output from the serial port:

Code: Select all

Jump to Secondary Boot
KOGNA 5.4.1 Build 17:11:16 Oct  7 2025
Flash Reading from Block 16...
Board Serial Number/Domain Kogna_SN159
Requesing IP Addr 192.168.0.11
KOGNA IP Address Assigned 0.0.0.0
No Ethernet Link

I imagine that this mean it is much more likely that the LAN8741A-EN is damaged, right?

Thanks,
Griffin Boyle

[TomKerekes]

That would be my guess