Solved Fried SB2040 badly - need some help

[Andreas]

Cheerio my friends, building a 2.4 and still not done.

I went for SB, Tap, Rapido hotend and a Fly SB2040 including UTOC board.

When I tested the hotend without LED, everything works fine. Hotend heats up, all sensors seem to be working. As soon as I connect the Neopixels to it, my SB2040 throws sparks. The first time I thought I had got the wiring of the LEDs wrong, therefore I tried it a second time with a new SB2040 and new LED string. The same happened, the chip throws sparks. The picture shows the component that will be fried (picture shows board being intact...)

I run the SB on 24V.

Question: Is there anything obvious I havent noticed? Is that a typical error? Dont want to do this a 3rd time...

Also: Do you know what type of component that is? Would like to repair the boards if possible

 

[Neil_I]

Which pins did you use to connect your LEDs?

 

[Andreas]

What do you exactly mean? I used the standard pads on the SB2040; Checked the wiring several times, used 2 different LED strips with the same result.

I also asked the guys over on the discord: my current guess is, that the origin used to be on the second part of the board and that there was a short between the 5V and 24V rail.

I'm kind of scared to fry the 3rd board now, but I will give it another try tomorrow. New board (both parts), new LED.

 

[Neil_I]

What do you exactly mean? I used the standard pads on the SB2040; Checked the wiring several times, used 2 different LED strips with the same result.

I also asked the guys over on the discord: my current guess is, that the origin used to be on the second part of the board and that there was a short between the 5V and 24V rail.

I'm kind of scared to fry the 3rd board now, but I will give it another try tomorrow. New board (both parts), new LED.

Just asking as you hadn’t posted a photo of the smaller board. I’ve seen a post in the past where someone had misaligned the 8 pin connector when refitting the SB front onto the printer, so that it connected to the wrong pins on the main board, and that made some magic smoke. Worth double checking yours, if you haven’t already done so

 

[Andreas]

Ah ok, I see. Well I checked the 8 pin connector and everything worked fine before connecting the LEDs.

I've setup a new SB2040 yesterday. No shorts between 5V and 24V; Hotend works fine, LEDs not attached. Kind of scared to try a 3rd time now... I measured resistance when power is off: no short between ground and 5V and no short between 24V and 5V rail. Live circuit shows 5.3V on the 5V rail.

 

[Andreas]

Ok, works now.

I checked everything I could beforehand. Replaced both parts of the SB2040 boards. Checked the LED beforehand on the PB0 pin on the Octopus board to confirm the LEDs are working. Checked the voltage on the SB2040 and it was fine. Connected the LED without the hotend (beforehand the sparks flew when both connected) and no sparks , but also no light . I did that in increasing durations, starting with the printer being on only for a second while watching the circuit with an IR heat camera When I felt safe I also connected the hotend and still no sparks but still no lights . Checked my wiring, found a dumm mistake which I corrected. Switching the printer on while watching with IR camera for increasing durations and finally everything works.

So the issue was a bad front board of the SB2040; I don't know for what reason but renewing not only the side board, but also the second one did the trick for me.

 

[xmonster]

That 5V power stage on the SB2040 seems quite bad, which results in unstable voltages. I tried to run rainbow barf + 8 Neopixel Fanboard behind clear 5015 housing and SB2040 got really hot and the LEDs glitched out if i gave them any brightness at all.

I suspect this is also why temperature readings are all over the place on that board, jumping around up to 1°C in my case.