Hi all,

I have a problem with my Anet A8 Mainboard, I soldered the net Atmega 1284P-AU Chip on it because it was bad. When I connect the mainboard to my DC Power Supply, I can see that it draws about 0.7-0.8A current on 12 Volts. The spare mainboard I have (working good) is typically on 0.2A. How can this be? Is there a possible short to ground? The component Q4 gets extremely hot I think it is because it is under high load of the 0.8A. My low Electrical toughts about this are that there is a short to ground, like a capacitor or resistor maybe?

https://github.com/ralf-e/ANET-3D-Board-V1.0/raw/master/ANET3D_Board_Schematic.png

Maybe somebody can help me. Thanks !

 

That is the regulator so it is getting hot from the high current.
What killed the original U5, and why do you think it was bad?
Are you sure you have soldered the new U5 on orientated correctly, with no solder blobs?
Check for other heating of ICs too, not just the regulator.
What does the 5V supply measure?

 

Hey thanks for the reply, I did not change the U5 i changed the Atmega chip. I killed the chip when I hooked up a sensor to 12V but left the COM hooked at Z_Stop Pin 3 which goes to the IC Chip. My thinking is that somewhere a condensator or resistor got fried too. I flashed the new chip with firmware it is working but as I said it drains too much current and the regulator gets too hot. Any idea what component could cause that?

Thanks again!

 

According to the circuit, U5 is the Atmega chip. I was just too lazy to type "Atmega 1284P-AU Chip"
With the power off, measure the resistance across each cap. And each Atmega 1284P-AU Chip pin to 0V.
Did you carefully check to see if there are no solder bridges?
When you programmed it, was the chip on the board and did you have it powered from USB or the 12V.
Can you unplug the motor drivers on your board?
If so, try with them removed.

 

Ok thanks I will do as soon as I get home...but with measure the resistance across each cap u mean capacitor or resistor? Sorry not that pro with terminology Yes i did it under a microscope and looked at the end on all legs, they look perfect no bridges.
The chip was on the board when i flashed it using my arduino uno, just used the connector to flash it with a bootloader, then hooked up 12V and usb to flash it with actual firmware from pc.
I dont have anything connected to the board except the 12V power supply :-/

 

caps = Capacitors.
Depending on their circuit placement, there sold not be any short circuits.
How did the board die to start with?
Have you checked all the other ICs for warmth? I would expect them to be quite cool.
The idea is to see if you can find where the excess current is going.

 

I made the following error so the board died.
I have an autolevel bed sensor, took the positive lead, hooked it up to 12v power supply, but left the COM/N/Negative lead at the pin: S_Z-3 which is going to the chip instead of using ground. Thats how I think I fried the chip, but now I think that something else is damaged aswell just no clue what it could be.
All other ics are cool, the u5 is the only who is getting hot...maybe the excess current goes all the way through the chip to the z-stop circuit?

 

Checked all caps, no shorts here. Checked all pins of chip with ground no shorts here :/

 

Just hooked up my DC Power Supply and set it to 12V and 0.2A, it wont drain all 12V just about 4.3V... anyway while "powered" I took my DMM and measured Voltages. I found out that there is a fluctuating Voltate (I know that this means there is a short). I first noticed this fluctuation from 0V to 0.2V up down up down.... I looked at the schematic and saw that it goes to the LCD jack, I measured the other test points arount the u5 chip and saw that there are some of these... Measured the LCD Jack pins and found that I get Voltage fluctuation on pins 4,6,7,8,10... So I think that the u5 chip may be broken? Cause the LCD Jack solder joints look good... just strange I bought 2 chips and both behave the same...

Any suggestions?

 

The fluctuations may be ok. The signals to the LCD are changing as it is written to.
With the display unplugged, is the current still high?
The 12V may have damaged something else.
Is the printer trying to work? Does it read the SD card, drive the LCD and move the motors?
If some parts work and others don't, that may be a clue.
Are you sure the replacement Atmel processor is the exact model? Without checking, I don't know if there are differences between various ones that could cause problems.
It is pretty hard trying to remotely debug a board
Unplug everything you can to see if you can find it. Just have the power supply, no LCD, SD card, motors or anything else attached.

 

Thanks for the reply. That sounds logical... I will try to plug all in and see if everything works. The chip is the same as far as I can tell from the model number. I just ordered another one from another guy on ebay will try that one too. Yeah I know its hard but maybe it will work . Another strange thing I noticed is that sometimes when I touch the multimeter probes on my board somewhere the amps on my power supply drop to 0.20A from 0.8A and it stays there... when I unplug it and reconnect it is again on 0.8A and wont drop anymore...all is disconnected except the power.

 

Hooked up all wires, display shows all good can control the menu but it wont do anything, no motor is moving nothing... i can see that the D1 led is sometimes only lit verryy small, usually it is not lit at all but typically it should shine bright when i pkug in power... can it be possible that i damaged the led d1 when i used my heatgun to desolder the u5 chip? Since then it only lights up very little but only sometimes...

 

Hmm.
A close inspection of the board is in order as surface mount parts can move when the heat gun is applied. My attempt to repair a board blew caps off the board. A good idea is to cover the board with aluminium foil, with just a hole where the part you want to remove is. press the foil down over the other parts to direct the hot air away.
Have you measured the 5V?
And, the current dropping from 800mA to200mA is a clue. Is it just mechanical? Try pushing the board with an insulated rod, like a plastic pen. See if it changes the current when moved. That sounds like a way to find the problem.

 

I looked all parts unter microscope all are in place... yes I get 5V... when i apply 2v and 0.2A to the led d1 it lights up nice... used a plastic pencil nothing happens...when i use 1 of my dmm probes and put it somewhere it dropped to 0.2A but next time i touch it there nothing happens...when i touch somewhere totally different it drops again...but now i tried to touch all and nothing happens...no dropping just sometimes.

 

Any other thoughts? :/

 

I now found out that when I measure the voltage with my dmm the Y1 either sides the current gets down to 0.2 and stays there. Is it possible that Y1, C30 or C31 are broken? Its that circuit where Y1 is located.

 

That would be stopping the crystal oscillating when you put a lead on there.
So it does show the high current is dependent on the processor running.
You did not yet say if your board has removable motor drivers or not.

 

Ok. So chip u5 is problematic u think? I have the motor ics soldered on the board with a heat sink for each motor. Did you mean that? On schematics its U1 U2... thanks

 

I have the motor ics soldered on the board with a heat sink for each motor. Did you mean that? On schematics its U1 U2

Yes. On some boards they are plugged in and it would help to unplug them for a test if you could. But that is not an option.
Other than U5 being crook, I don't know what else to suggest.
There may still be a short somewhere so as you have another board, one thing could be to measure the resistance to oV and +5V of all the processor pins and compare that to the good board.

 

Nice thanks again for the reply I will try that. One more thing I notice now when you tell me about the motor control chip, when I let the current at 0.8A the regulator gets hot of course, the u5 chip but I feel that the motor control for the X axis is getting hot too...cant tell if burning but i can feel it. The other control chips are not hot at all...could that be my problem? I could remove the control chip and resolder it, but how to put the heatsink on again?

Thanks mate I really appreciate your help!