Anet A8 motherboard died

[James Shoemaker]

     Was printing happily and the printer stopped and went black.  The power supply is still putting out 12V, but if you leave it unplugged for a bit, then plug it back in, the printer boots, then when you turn on the heaters it goes black again.

    I think I need a new control board.  Do I just get the same one again or do I look for an upgrade board?

James

[Caroline Longnecker]

Kinda sounds like it might be a power supply issue. Do you have a spare you can test with?

Caroline

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[James Shoemaker]

   I stuck a meter on the supply and it sits rock solid at 12.5 through bootup and even when you turn on the heaters and the screen goes blank.  Wouldn't the voltage drop if it was a PS issue?

[James Shoemaker]

   was looking at one of these  https://www.ebay.com/itm/3D-Printer-Anet-A8-Plus-DIY-Motherboard-V1-7-Ramps1-4-Update-Version-Mainboard/303616326831?hash=item46b0f17caf:g:T-oAAOSwREZfAq7E

[beernutz]

Could the voltage stay the same but the amperage drawn still be a problem?  Asking because i am not sure.

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[James Shoemaker]

   I don't think so, if the supply can't deliver the Voltage would drop.  My first thought was Power Supply also, but when it tested at 12.5 with no noticeable ripple when the heaters cut in and the board shuts down I didn't think so.

[Ray Scheufler]

If the 12V rail is stable, I'd recommend checking the 5V rail. The anet board has a 7805 equivalent surface mount linear regulator that makes the 5v rail from the 12v rail. I suspect that something has gone wrong with one of the heater mosfets and it causes the 5v rail to drop when the fet turns on.  You will have to find a schematic of your board so that you can find a 5v pin to probe. The anet board doesn't have a bunch of unused pins so you might have to unplug things to find a 5v pin.

Tests to try:

Turn on the printer but do not turn on heaters, use the LCD to command movement and homing. My theory is that everything will be fine and this narrows it down to the heater circuitry. 

Turn on only one heater at a time (either the bed or the hot end). Again, narrowing down to what has failed.

If you have isolated it to a single heating output, try unplugging that output from the board and seeing if it still dies. This is trying to isolate board issue vs some other external issue.

I have an anet a6 in my basement. I believe that it has the same main board as your a8. I also have a btt 32 bit board that I bought as an upgrade for the anet that I'd be willing to sell you. I'd have to look up what I paid, but pretty sure it was < $40. I also have a couple of external fet boards that you might be able to use instead of thr bad outputs on your board.

Ray Scheufler 

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[James Shoemaker]

   I thought about digging into the board, but a new board was $30 on ebay.  replacement exact match board on the way.  Though the new one seems to be able to support running on 24V, would that be a good upgrade?

[James Shoemaker]

   There was a strong burned electronics smell in the enclosure when I opened it to check on why things stopped printing.

[Ray Scheufler]

Replacing the board is probably the best idea. If you dont want to wait for the slow boat from China I can loan you the electronics off my anet. I dont use that printer (and honestly if someone wanted to buy it from me I would entertain offers).

Converting a 12v printer to 24v would require that you replace the heater cartridge in the hot end and replace the heated bed. Since the hot end and bed are both just resistors when you double the voltage that will double the current which will end up quadrupling the power. You probably dont want to quadruple the power draw on those. There is a chance that the heated bed can be converted between 12v and 24v. Some models have the pcb trace split in half and you either run them in series for 24v or parallel for 12v.

In theory the stepper drivers and stepper motors themselves are fine with 24v, you have to just make sure that the board is compatible. 

Ray Scheufler 

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[James Shoemaker]

   the 2-4 weeks of shipping will allow me to concentrate on other hobbies, it is spring and as the big room with the blue ceiling warms up my thoughts turn to boating anyway.