Anyone better at the EE side than me willing to take a look at this?
I think this board is shot, but I’d like to better understand what is happening here.
The white “<-” points to the “FAN0” connection. It’s the connector for the part cooling fan. It should be at 0V until it receives an M106 SXX command setting a voltage between 0V->12V. As you can see the voltage is inverse to the SXX value. The decrease is voltage is linear so some control is still present, but I’m at a loss to figure out where the rogue voltage is coming from.
Only things connected to be board besides the “FAN0” I’m measuring here, is the power supply and the USB cable.
I can swap to the “FAN1” connector and change the pin in the firmware, but I’d like to get a better idea of why this is happening and how to measure it.
Is there a schematic available? I’m thinking the device controlling the power to FAN0 is not being controlled properly. Check to see if the power transistor attached to FAN0 has a resistor that keeps the transistors control pin high or low, and see if its working. The transistor controlling the fan may be floating, and the CPU may not be able to control it because of that damaged component.
If the part in question is a relay, the relay may be damaged or faulty, and just needs replacing.
This is a dirty board. It also looks multi-layered. Lets start with this.
Take a soft small paint brush and a vacuum and clean the dust off the board and especially away from the IC pins.
Then i would take a soldering pencil and retouch each of those connections. The diode above the 100 resistor, both ends look like it has bad solder connections.
NOTE: This is where it comes in handy to have a cheap usb microscope to zoom in on each component to look for cracks. SMD parts can crack from too much soldering iron heat. If you can do that, then have a look.
Then take a multimeter to check each of those components for stable readings. Unstable components are most likely damaged and need replacing.
Retest the board for correct function. If problems persist, while under test, use a freeze spray with the narrow straw to spray each component (including the cpu) The cooling spray will cause a temperature differential in the SMD part and any component with an intermittant connection will highlight the failure when hit with the spray.
This is how any electronics tech would identify a faulty component. I am assuming you don’t have an oscilloscope either, and you don’t need one for this test approach. If this (1-4) does not identify a faulty component, then more problems are happening with the board.
@MidnightVisions Wow, cannot thank you enough! This is unbelievably helpful. Those techniques and tools needed are what I need to know at the moment.
Yes, it is multi-layered and it’s very dirty. The Delta it came from did not have an enclosure for the board and sat exposed under the build-plate. I’m already planning on a printed enclosure for the Deltesian, whether this board or a new one.
I could get a hold of an oscilloscope, if it was really necessary, but it’s such a cheap board, I’m more than fine with replacing it. I’m more interested in understanding what wrong, and fixing it is a secondary concern.
If you get a second board, use a multimeter to compare the components of the new board with the old board. Direct comparison will also help you find the differences.
I’m seeing the Mosfet on FAN2 looks like it released the magic smoke.
But I’m not really understanding anything else I’m seeing. Is there somewhere that I could reference to get an idea of what good connections look like?
@MidnightVisions Alright, I got it. The FAN0 104 resistor is only reads 0.479kΩ when it should be 100kΩ. FAN1 reads 98.7kΩ and FAN2 reads 53.3kΩ.
It seems I can just swap the FAN0 pin to FAN1 pin and not use FAN0. Is there any issue there?
Also, does FAN2 reading 1/2 the expected resistance mean it’s failing?
Also, knowing the FAN0 resistor is now 1/200th of the expected value, would it be possible to still control it, or even just accept it and use the 8v output?
The resistor is cracked, so needs replacing. The easiest thing to do is just replace the bad resistor and don’t do any other changes. If you don’t have access to a replacement part, you can swap the bad resistor with one from FAN1 or FAN2. If you just use FAN1 instead of FAN0 you will have to go through your g-code file and manually change each command for FAN0 to FAN1.
