Hi all, I'm facing an issue of which I do not have sufficient knowledge. The SKR1.4 is driving the old Replicator wonderfully but when the bed is heating, there's a high pitched sound coming from the electronics board. #define MAX_BED_POWER 255 // limits duty cycle to bed; 255=full current in Marlin. I am afraid to lower it because I understand this will put strain on the MOSFET. Should I check the bed's resistance? I did and it is 4,7Ohms Should I build a circuit with a power mosfet to drive the bed power? Should I limit the current through the firmware? (Marlin). It's a 24v system. I've never heard this noise and don't know if it's good or not. Update: I did some more research and found this: [github.com] It says: [attachment 116330 Screenshot2020-07-31at22.49.05.png] According to this website: [ohmslawcalculator.com] A heated bed with 24v and 4,7Ohms of resistance should pull this: [attachment 116331 Screenshot2020-07-31at22.43.54.png] So, if the SKR 1.4 can deliver 144W to a bed with higher than 1Ohm resistance, and according to the formula my bed pulls 122W and has 4,7Ohms, that should be safe right? So, I'm wondering, where could the high-pitched wine be coming from? And is there maybe a way to limit the current draw of the bed through Marlin by using a lower PWM signal or some tech? https://reprap.org/forum/read.php?13,875697,875697#msg-875697 Sat, 16 May 2026 14:03:24 -0400 Phorum 5.2.23 https://reprap.org/forum/read.php?13,875697,875744#msg-875744 https://reprap.org/forum/read.php?13,875697,875744#msg-875744 Ohmarinus Controllers Sat, 01 Aug 2020 18:44:29 -0400 https://reprap.org/forum/read.php?13,875697,875697#msg-875697 https://reprap.org/forum/read.php?13,875697,875697#msg-875697
I'm facing an issue of which I do not have sufficient knowledge. The SKR1.4 is driving the old Replicator wonderfully but when the bed is heating, there's a high pitched sound coming from the electronics board.
#define MAX_BED_POWER 255 // limits duty cycle to bed; 255=full current in Marlin. I am afraid to lower it because I understand this will put strain on the MOSFET.

Should I check the bed's resistance? I did and it is 4,7Ohms Should I build a circuit with a power mosfet to drive the bed power? Should I limit the current through the firmware? (Marlin).

It's a 24v system. I've never heard this noise and don't know if it's good or not.

Update:
I did some more research and found this:
[github.com]

It says:
[attachment 116330 Screenshot2020-07-31at22.49.05.png]

According to this website:
[ohmslawcalculator.com]

A heated bed with 24v and 4,7Ohms of resistance should pull this:
[attachment 116331 Screenshot2020-07-31at22.43.54.png]

So, if the SKR 1.4 can deliver 144W to a bed with higher than 1Ohm resistance, and according to the formula my bed pulls 122W and has 4,7Ohms, that should be safe right?

So, I'm wondering, where could the high-pitched wine be coming from? And is there maybe a way to limit the current draw of the bed through Marlin by using a lower PWM signal or some tech?]]> Ohmarinus Controllers Fri, 31 Jul 2020 13:31:59 -0400