Fuses fusing musings

[drunkenmugsy]

First major issue - I popped the F3 fuse. It was weird how it did it. I had installed one more layer fan and rebuilt the hotend after a PLA jam. Had to acetone soak the tip and the plastic spacer. I ordered a couple extra but the soak didnt seem to damage the stock original. Got it all back together. Was extruding some black abs. Everything was going fine. Got the jammed PLA micro fragments all out. Extruding just fine. Fans fine, LED ring and hotend led heating indicator fine. I homed it a couple times, fine. I X Tower adjust once, fine. Make a small endstop tune. X Tower adjust again and right before it goes where it is supposed to it stops, about 2cm above the bed and everything goes dark. PSU has power. I checked the fuses. 15amp is fine. Got out the multimeter, F3 is bad.

My question is did adding another layer fan do this? A bad solder? I have both fans going to 1 connector going to the layer fan tab on the rambo. Both stock style fans in the stock layer fan shroud.

Could the thermistor shorting out cause this? When I rebuilt the hotend the thermistor insulation was backed off a couple mms at the hotend. I left it because it was all taped to the hotend wires. It could have made contact with the hotend itself. But it doesnt look melted/damaged at all.

[Eaglezsoar]

See this link: http://forum.seemecnc.com/viewtopic.php?f=36&t=5775

F3 does control the extruder (hotend) and the fans and depending the version of the Rambo it also controls the logic on the board.
Most occurrences of F3 blowing is an intermittent short of one of the fans or the extruder. Check your wiring carefully of the fans and hotend and make sure that
a short does not exist. Shorting the thermistor will fry the particular thermistor logic circuitry on the card but rarely the F3 fuse. If you are troubled that the fans are
pulling too much power you can replace the fuses with 10 amp versions which is permissible according to the manufacturer of the Rambo.

[Earthbound]

The load of a 2nd layer fan will not cause F3 to pop. I run 3 stock type layer fans and have some LED lighting that also feeds through F3.

Shorting the thermistor leads together shouldn't pop F3. Shorting the grounded thermistor lead to the positive lead on a fan circuit or hot end will knock out F3 immediately.

[Eaglezsoar]

The load of a 2nd layer fan will not cause F3 to pop. I run 3 stock type layer fans and have some LED lighting that also feeds through F3.

Shorting the thermistor leads together shouldn't pop F3. Shorting the grounded thermistor lead to the positive lead on a fan circuit or hot end will knock out F3 immediately.

Agreed and thanks for the better wording, shorting any of the components to ground will likely lead to a blown F3 but I like the way you worded it.

[drunkenmugsy]

Thanks for the replies. I was pretty sure the 2 fan load was not enough to trip a fuse based on what I have read. I will stick with the stock 5amp fuses. Ordered them already just waiting on delivery now.

I didnt heat shrink some of the connectors on the hotend yet as I planned to add more stuff. I think what may have happened is as the effector was moving the wires got pulled together, shorted and popped the fuse. Thinking this might happen during the build I have tried to put the connectors at different lengths so they are not all in the same area and height. I will check this more carefully once I get some fuses back in the beast and eventually sleeve them all so it wont happen again.

[Eaglezsoar]

Thanks for the replies. I was pretty sure the 2 fan load was not enough to trip a fuse based on what I have read. I will stick with the stock 5amp fuses. Ordered them already just waiting on delivery now.

I didnt heat shrink some of the connectors on the hotend yet as I planned to add more stuff. I think what may have happened is as the effector was moving the wires got pulled together, shorted and popped the fuse. Thinking this might happen during the build I have tried to put the connectors at different lengths so they are not all in the same area and height. I will check this more carefully once I get some fuses back in the beast and eventually sleeve them all so it wont happen again.

Sounds like a great plan, best of luck to you and your printer.

[415porto]

I did the same thing and couldn't locate a fuse yesterday so I made one (temp only). [img]https://scontent-sjc.xx.fbcdn.net/hphot ... e=55B99FA3[/img]
[img]https://scontent-sjc.xx.fbcdn.net/hphot ... e=5579629E[/img]