Power supply cable problem - GT2560 a+ nearly burned !

[Dilbert0815]

Hello

Thanks for your replys Dilbert

I have a nice milliohm meter somewhere in that horible pile of stuff in my basement. I will try to find it and mesure the resistance of the heatbed, let's says hummm in 20+ more hours (because it's printing atm).

Maybe we have a problem of very low resistance with the heat bed ? Really i don't know.

From the pics i send, i "seems", but i can be wrong, that the connector already got a nice solder bridge between the two +12V pins. Maybe the solder joint was not good ?

Got an answer email from geeetech :

Hello,
Thanks for contacting us!
Hope you have a great day!
Thanks for your feedback!
1.We think the issue lead by the poor contact between PSU and motherboard
2.There is a problem with the PSU input soldering of the motherboard
3.The 180W psu is not suit for your printer(We have upgrade it to 230W)
4.If it allows, we suggest you upgrade your PSU to 230W.
5.You can contact the sales to send you the new motherboard.

Regards

2.There is a problem with the PSU input soldering of the motherboard
This one !

Bad solder joint can result in lost of contact inside the joint (cold solder anyone ?)

I still think that the board desing should joint with a PCB trace the 2 +12V rails, and the schematics clearly not showing this joint. AND a better connector + more gauge on the power supply cable could definitly solve the problem.

No, your pictures show there was a problem in the connector. Most likely its the two tin foil connector pieces carrying the whole heat bed current.
The solder getting week on your board is the RESULT of the connector overheating. If the solder would be the problem then the burn marks would be lower at the board surface.
Moreover you solder showed it has melted! A cold solder would not cause melted solder, because then the cold solder would have healed itself!
Your pictures clearly show the problem is in the middle of the connector, not at the board.

I haven't told that in my case the connector pin pulled itself from the board after the tin got liquid, cutting of the heat bed of.
The thermal runnaway reacted to the heat bed dropping low while being supposedly powered.
So we two had almost the same case of connector failing.

Disecting my failed connector clearly show that the heat center was at the connection between the two connector metal parts. So it's the contact itself.
What I havn't measured yet is the actual current draw of the bed, but I have a power meter at the socket and that shows around 260W total when the bed starts. That excludes the hotend (Slic3r code starts head bed first), but includess the motors and base electronics.

Assuming 230W for bed, I get around 0.85 Ohm bed and ~16A current. Agreed, thats realy stressing to the max.

[Gingko]

May I ask for more detail?
It happened during printing or heating before print?
What kind of material? ABS?
If it's during printing, how long has it printed before burned the connector?

So that we can make a reproduce.

[Dilbert0815]

May I ask for more detail?
It happened during printing or heating before print?
What kind of material? ABS?
If it's during printing, how long has it printed before burned the connector?

So that we can make a reproduce.

You may, but these data is rather useless to reproduce anything.
We are speaking here about connectors that change parameter after several connections.
As for my printer the board was assembled/disassembled already a few times during upgrades and modifications.

When it burned the bed was just set for 55°C for PLA at the begin of a print. But It survived ABS and 120°C bed some weeks earlier.

What you can believe from the practitioners here is that using a connector thats rated for 10..12A max at this current for longer time is critical and should be avoided. Using single connector pairs makes this worse as a degrading connector after several disconnections has no fall back.
Just read carefully the suggestions and learn.

[_kaktus_]

...
Just read carefully the suggestions and learn.

This is very rude on your
If you don't know and don't understand why Gingko collects this data, don't judge.

Allow me not to explain to you the reason for these questions.

[Dilbert0815]

...
Just read carefully the suggestions and learn.

This is very rude on your
If you don't know and don't understand why Gingko collects this data, don't judge.

Allow me not to explain to you the reason for these questions.

Sorry, I didn't ment to be realy rude.

But these printer sets are just kits. They are mostly not assembled and left this way like preassembled products.
So when it actually failed it has rather few to do with what went wrong.
You got quite a few data already in this thread for a engineer to have a good picture of what are (potential) root causes. Both reporter (exodius and myself) have an engineering dergree and delivered quite a lot of detail data.

The questions from ginko are in contrast rather basic usage questions. They would not give you any real inside what went wrong, as these connector problems have a high degree of randomness and depend on the further history of usage and assembly. They may be statistics, but not realy more.
Moreover, for someone with an engineering background these questions rather tell me that the quite detailed posts here have not being realy read casefully. I would also think that kind of rude to the reporter of the problem

[_kaktus_]

I understand it all.
So I'll explain the stuff. The Geetech team wants to create similar conditions to experimentally investigate the case of this defect.
It is often the case when we do not know certain facts, the matter looks different.

Personally for me, the subject is clear, as I expressed in my statement at the beginning of the thread.

I am glad that you have apologized our forum gem Gingko.
And I greet you cordially.

[keyser187]

mine hasn't melted or caught fire yet, so what do us non-engineers (stupid people) do to make this safe?
i have also done what i've seen other people do and turn the board around so the stepper drivers were aligned with the fan, so that molex connector is at the top on mine, will this affect it somehow?

[_kaktus_]

Hello.


This definitely does not affect the power connector. But there is a recommendation for stepstick modules.

ps.
No man is stupid

The problem with the power connector is the weak contact between the pins of the socket and the plug.

If you often disconnect the power cables, you can pull out the pins of the plug and tighten them gently with a pair of pliers.
To pull out the pins, you must release the latch.

[keyser187]

ok thanks,
whats the recommendations for the steppers? ,i thought you just had to keep them cool along with those mosfet things
i know you have to release the latch before pulling the molex out, i'm not that dumb, i've just never done electronics or engineering so its all new to me
(but that's what YT is for i suppose )
also is it a good idea to print off a housing to go over the board with a fan attached to keep it cool?
because dont coiled/bunched up wires get hotter as the heat is concentrated in one spot?
https://www.thingiverse.com/thing:2557414
https://www.thingiverse.com/thing:1720745

Ps. ive seen some VERY stupid people in my 38yrs of being in this messed up world, and im probably one of them

[_kaktus_]

New problem / question = new topic