Voltage regulator for fans

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jkcab95
Posts: 9
Joined: Sat Jul 11, 2015 6:17 pm

Voltage regulator for fans

Post by jkcab95 » Wed Nov 11, 2020 12:32 am

I have a GT2560 board from 2015 with not a lot of time on it. It is on my i3 Prob kit I built. I updated the firmware to 1.1.9 so I could add a BL Touch in the future and to be able to use Linear Advance.
I was having trouble with my part cooling fan and was able to finally figure out what was going on in the firmware to get it going again.
While I was tweaking firmware and doing pid tuning I noticed all my fans stopped working? Q5 is still receiving a signal and it varies with speed adjustment from .5 - 5 volts. I have looked at the schematic for the board but am having trouble determining where the voltage regulator is that supplies the 12 volts for the fans. I disconnected everything from the board except the power cable and measured the voltage at the fan pins. I get 10.3 volts. When I connect a fan they all drop to 3.7 volts?
I was wondering if someone could tell me where in the circuit is the 12 volt regulator for the fans? I see an 1117l-3.3 low dropout linear regulator that supplies 3.3 volts. I see an LM358 opp amp but no regulator?
I have spent a considerable amount of time on this printer doing upgrades and getting the firmware working correctly. At this point it is starting to nickel and dime me or I would just buy a newer board.

Any help here would be most appreciated,
JKCAB

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