A10 - GT2560 V3 (!) - no PWM - 24V steady full power

[realfox81]

Hi, i have bought a refurbished A10 were the filament cooler did not work. I have wired in a new filament cooler and now the filament cooler stays at 24V it means it blows the whole time with 100%. I would like to have it like on my other printers that the part cooling fan kicks in when layer 2 have reached so the print sticks better to the bed.

I have read something about firmware updates, yes i did this with the official firmware from geeetech -> fan stays 24v 100% the whole time

I have read about some JP2 jumper, but my board does not have this jumper ist Rev V3 not Rev B they look the same but they are a bit different.

I suspect the mini-connector-board between the hotend and the mainboard is maybe wrong, but without ordering a new one i do not know.

Where are the PWM Ports to the GT2560 V3 wired? There are only Fan1 and Fan2 ports both have 24V the whole time. They are not PWM Controlled. Where are the PWM Ports?

Thanks for helping,
Stefan

[William]

I think it will help you to find it:
https://github.com/Geeetech3D/Diagram/b ... .0_SCH.pdf

[bernte_one]

Hi Stefan,

next days i get an A20 with rev3 Board, i am also interested whre to find the right connections.
Did you find a jumper or so?

Otherwise try the Marlin 2.0.xx firmware from Vertabreaker here in Forum.
You can do most settings by this firmware on lcd.

As i remind from my older A10 and Rev B Boar PWM just work if you set the jumper nearby the fan connection.

best regards from Germany

[realfox81]

Hi all,

i found in an video were the PWM outputs might be. I upload a screenshot from this video. I have to try it out first at home.
Its on the connector which comes from the hotend. It shows the old rev B which might pin compatible with Rev 3!

There is no jumper on my board, this place is empty.

I have somewhere here in the forum read that the connector board near the hotend might be the problem, maybe there are bridges on the board -> i have to check @home first.

I will try marlin 2.x, hopefully the pwm fan will work then.

Best greetings from germany too!

Stefan

05-03-2019 09-51-33.jpg (142.95 KiB) Viewed 10190 times

[Chris81]

Hi realfox81,

Maybe we are from the same age, and same country

Be aware about the screenshot you posted above. GND in the picture is wrong, it is the output of a MOSFET (for example Q2) and depending on the PWM signal it can become a voltage like GND. The "Plus" is VCC (24V) all the time. When the PWM signal is off the MOSFET output will follow VCC, so there is nearly no voltage drop over the fan, fan is off. When PWM is on and the value goes up to 255 (=100%), the MOSFETs restistance will become smaller and smaller, all voltage will drop over the fan =on.

To find your bug, i would suggest the following steps:

• disconnect the extruder cable from the GT2560 like in your picture

• take a multimeter and measure the voltage at pins of your picture

• vary the PWM signal in the printers menu

• if the voltage changes between 0-24V everything is fine on the board and the problem must be in the cabling or the small pcb at the hot end/extruder (maybe a short)

• if the voltage does not vary with the PWM signal the MOSFET is defective (change it) or the PWM signal is not present

• you can try to measure the PWM signal directly at one of the resistors before the MOSFET (see schematic of GT2560). Be careful to not short anything, or your board can be damaged, i burned my main fuse the first time

• if the GT2560 is fine, disconnect all cables from the extruder pcb and disassemble the pcb, look for unclean soldering points at the pcb

If all these steps does not help, you have to check all wire connection for switched cables, but this is a little bit of work. You have to compare the GT2560 schematic with the picture of the extruder pcb (find it in the Geeeetech store) to find out which cable has to go to a specific pin at the extruder pcb. This can be difficult if you do not have practise in reading schematics.

Greetz Chris

[realfox81]

Hi Chris,

i have now 3 geetech a10 and a10m here most of them with the same errors. Seems to be a production problem of early models all of them are 2018 models. The first a10m has no pwm output its always 24v, the second a10m has no pwm output the fan blows all the time. The third a10m behaves normal, the pwm signal seems to be working, as the fan can controlled by the display.

Can you show me were to measure the mosfet on which contacts? I followed the traces from the fan through the small pcb down to the motherboard and this is were the contacts go into the gt2560.

Never had any problems with pwm fans, i used a lot of boards in the last years, but the geeetechs boards seems to have no quality control at all.

I got all of them defect, but most of them has defective fuse (littlefuse 10a) and also defective stepper driver, which is a easy fix, but now the pwm fan seems to be not that easy.

I also installed Marlin 2.0 into the A10 board, but no pwm behaviour at all - fan blows 100% all the time, even if the fan is set to off, either in the display or pronterface by gcode command.

Best regards,
Stefan

[Chris81]

GT2560_V3_Measure.png (725.23 KiB) Viewed 10058 times

Try to measure after the picture i made (see attachment).

1.Disconnect the extruder cable. You can also disconnect the little red pcb with motor driver (like on the picture). Turn on the GT2560 and measure from Pin 9 to 6 of EXT2 (Do NOT take 5 instead of 9 because its more dangerous there to do a short and detroy the board ). Vary the PWM signal in the printer menu, the voltage should drop from 0-24V. If it does not go on with step 2 otherwise go to step 3.

2. Try to measure the PWM signal coming from the microcontroller: Measure from GND (Pin 11 of EXT2) to one side of the resistor R57. It is marked in the picture and difficult to reach(!). Here the voltage should drop from 0-5V (or 0-3V, i´m not sure at the moment) with varying the PWM signal. If it does not the microcontroller must be defective => get a new board . If it does the MOSFET Q2 must be defective=>change it. Double check the MOSFET: Turn off the GT2560 and measure from GND (Pin 11) to to Pin 6, if its shorted the MOSFET can(!) be defective. With your first MOSFET measurement you proved it .

3. Go back to my first answer above "...everything is fine on the board and the problem must be in the cabling or the small pcb at the hot end/extruder ...."

Let me know if this worked for you.

[realfox81]

Hi Chris, i have already read your post, but i didnt had the spare time at home (3 kids) to measure the board. I hope i can do the measurement soon. I will reply. Greets Stefan