Desoldering the Darlington

[Titus 170]

As concluded in multiple topics the always on problem for the fan on the hot end lies with the Darlington(UM1) transistor most of the time.So I got a replacement at the Ulti-evening and now I'm trying to desolder the broken one. But it's giving me a hard time.

I've managed to get the bottom pretty much clear, but since there is a via, the top is also soldered. I'm not sure whether to snip the darlington off so I can try to pull each pin out individually and clean up with desolder wick. I'm afraid I won't be able to grab the pins anymore.

Any advice?

 

 

[IRobertI 521]

Yup, I would do as you suggest yourself and snip the legs off. Cut them as close to the body of the transistor as you can to give you something to grab and then pull the legs one at a time.

Or you could add more solder on the back of the board so that you can heat all three pins almost at the same time. Then wiggle the transistor out a bit at a time as you drag your soldering iron across the three solder points on the bottom of the board. The first option is less risky though IMHO.

 

[Titus 170]

Thanks for the reply. I tried the last option already, but I can't really heat 3 pins at the same time. So snipping it is.

What happens when you don't have anything in place of the darlington(i.e. I snip but I can't de-/re-solder)

 

[drayson 75]

I would suggest to snip it of and use some kind of desoldering wire (kind of copper mesh) to clean the holes. I always get the things done pretty clean.

[gr5 2,270]

Be gentle - the traces built into the board are very thin and it's easy to damage/rip them off.

The snip method is superior. Remember - even if you can't get the old pins out you can solder the new pins to the old pins. But don't - just pull them out gently rocking them back and forth after the solder is hot from the other side. Apply liberal amounts of solder to let the heat flow nicely.

 

[Titus 170]

Mission successful, pins are out, soldered a new one in. Assembling now, will let you guys know.

I'm servicing my UM totally, for the first time that I've had time for that since I bought it second handed. So after this I will work on the huge amount of friction while moving the printhead, and the NOT so flat printbed Perhaps I'll open up some more topics along the way.

Thanks!

 

[gr5 2,270]

I will work on the huge amount of friction

 

Check the 8 endcaps on the 4 XY rods in the upper corners of the machine. Often the rod is too long by a tiny bit. There are lots of solutions on thingiverse. Or you can use shims such as washers.

 

[gr5 2,270]

and the NOT so flat printbed

 

Wait for the heated bed upgrade. It's worth the wait.

 

[Titus 170]

:cool: Fan is working like it should now!

EDIT: Perhaps We should fork this post(and your two) into a new topic?

/offtopic:

Thanks for the endcaps idea. I'll pursue that. Also I am going to look at my pulley alignment and the XY blocks, I think there is some friction there too due to the screws. Ideas?

As for the printbed, the wood is curved and when I try to level the bed I can't actually move all four points up and down, some only down, others only up... This is not the main problem, but when a print starts, it zeroes, the Z endstop triggers when the tip hits the printbed. But when going to the start after purging the nozzle, it starts like 3 mm above the printbed. Though I can fix this in the start Gcode, I believe it should be fixed on the machine. Ideas?

 

 

[gr5 2,270]

You should really start a new topic. Also better to post 3 images instead of 1 album - when you click my media brows images (not galleries).

I think you simply need to slide the Z endstop switch. It's in two very long tall grooves so that you can slide the Z endstop switch up or down as needed.