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Heating problem MKS 1.3

Posted by Bernie 
Heating problem MKS 1.3
May 31, 2019 08:56PM
I have a corexy RepRap custom built printer. I have only one problem. The hot end will not heat. The thermistor functions perfectly. The hot end heats when voltage applied separate from the MKS board. The tft screen reads the correct temp and shows when the user calls for heat by raising the setting. The hot bed works in entirety perfectly. All other systems/functions also work perfectly. Jog all directions home all axis’s. Fans work perfectly. My original attempt was from pin 2.7 on the MKS 1.3 board. When it failed to work I moved to pin 2.6. It does not work either. I have used a multimeter on both pin set and the 12vdc required is missing. I am at a loss. Please help
Re: Heating problem MKS 1.3
May 31, 2019 11:08PM
from the fact that your pin numbering is for eg 2.7, ill presume your talking about a MKS sbase 32 bit board

the schematic [github.com]

looks like its gnd switching like most repraps... so the 12v side should always be 12v and its the same line as power to the stepper drivers... check with respect to gnd on power supply.
Re: Heating problem MKS 1.3
June 05, 2019 08:30PM
I have a 24vdc power supply. 12vdc is created via a boost Buck unit. Not positive what your saying. The 12vdc goes directly to the power terminals of my MKS 1.3 32 board. The terminals are labeled pos neg and are connected positive coming off the boost Buck to positive on the MKS board, likewise the negative. Doesn’t the MKS board distribute the positive 12v to the appropriate terminals/contracts/etc. ? Am I missing something? All the devises, power supply, boost Buck, mosfet, tft are all isolated on plastic mounts. I don’t believe I have a common ground throughout. Just trying to understand what your saying. Thanks for taking the time to help me. I am so close to printing. This single issue is frustrating me.
Re: Heating problem MKS 1.3
June 05, 2019 10:57PM
I presumed you had a 12v supply not 24v

From what I see on the circuit diagram there is a 12v generated, but it is only used to power the buffers to turn a 3.3v signal into a 12v signal to turn on the mosfets.
If one mosfet works they all should.... (unless there is a hardware fault)

So on your mosfet outputs should be 24v on the + pins and a switched gnd on the - pins.
Check you have 24v on the + pins of your mosfet plugs with respect to the power input gnd.
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