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HeatBed power cable broken  

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serge.k
(@serge-k)
Active Member
HeatBed power cable broken

Hello M. Prusa and forum,

making this thread to report about a problem with my Mk2 upgrade. (self built)
What happened is that during a long print I noticed that the heated plate didn't keep it's temp anymore, from the initial 85° set, it had 74° left, ... this made me watch it closer for a time, and it would drop very slowly like 2-3 in 30 mins more or less ...
luckily my long print finished without any problems, but by the end the plate had cooled basically to room temp.

ofc, the first thing I did was investigate the problem and found pretty fast that one of the power cables below the cover plate, covering the soldering on heat bead was broken, basically it had started melting and was soldered to the cover plate at the removal.
Further investigation showed that it probably was an assembly mistake (my mistake), the broken wire had been squashed and damaged while tightening the cover plate. It then heated up under the load and broke after a certain hours of printing... (eeeps ... could have burned down my flat in worst case)
So even though it seems to have been a slight cable routing issue on my part, I would like to point out that I had no way to notice that there was a problem there, and looking at the cover plate, I must say there isn't much place to pass the cables, or better said, the solution is not optimal, because a slight mistake can have bad consequences (high power current on plate)
a pic in the end of what it looks like
https://1drv.ms/i/s!AmhL7B0FeTgNgtVDtwK4tMQFHRKqog
Maybe M. Prusa can find a better solution for this on Mk3 🙂 ...other wise great machine!!!
KaiTech

Veröffentlicht : 26/09/2016 9:25 pm
erron.w
(@erron-w)
Estimable Member
Re: HeatBed power cable broken

Out of curiosity, did you have the nylon filament inserted in the cable tie put in properly around the cables and cover? This should provide the strain relief to prevent that.

On the whole though that looks to be a pretty easy fix if your handy with a soldering iron 🙂

Veröffentlicht : 27/09/2016 6:57 am
frank.s
(@frank-s)
Active Member
Re: HeatBed power cable broken

Hi Serge

looking on that picture maybe a small second thing to fix:
The resistor R1 seems to have suffered a bit as well. Maybe if you have the soldiers iron hot it might be a good Idea to fix / replace that one as well?

All the Best
Frank

Veröffentlicht : 29/09/2016 4:18 pm
serge.k
(@serge-k)
Active Member
Themenstarter answered:
Re: HeatBed power cable broken

Hello all,

just wanted to let you know that the MK2 is back up and running. I replaced the broken wires with some super flex high current cables from RC shop. thy should be significantly more resistant to any possible movement strain.

and just to follow up on the questions, jes I had the Nylon filament bound in with the cables. and I think it would have worked would there not have been the issue withsquashing the cable while assembly.

Also I had a close look at the R1 resistor, it looked ok to me so left it and it seems to be fine so all good. Thanx for the heads up.

Anyways the problem occurs from the to tight exit for the bundle of cables in the cover plate. After instection I noticed that mine had some hard edges where the cable past through, (3d printed part) so I cut and beveled it out a bit and now it should keep for ever...

cya and have fun printing!
Serge

Veröffentlicht : 01/10/2016 10:57 pm
Linux User Group Oberschwaben
(@linux-user-group-oberschwaben)
Estimable Member
Re: HeatBed power cable broken

Hello all,

just wanted to let you know that the MK2 is back up and running. I replaced the broken wires with some super flex high current cables from RC shop. thy should be significantly more resistant to any possible movement strain.

and just to follow up on the questions, jes I had the Nylon filament bound in with the cables. and I think it would have worked would there not have been the issue withsquashing the cable while assembly.

Also I had a close look at the R1 resistor, it looked ok to me so left it and it seems to be fine so all good. Thanx for the heads up.

Anyways the problem occurs from the to tight exit for the bundle of cables in the cover plate. After instection I noticed that mine had some hard edges where the cable past through, (3d printed part) so I cut and beveled it out a bit and now it should keep for ever...

cya and have fun printing!
Serge

Hi serge,

What cables did you use ? Can you provide a link ?

Thanks!

Veröffentlicht : 02/10/2016 11:21 am
serge.k
(@serge-k)
Active Member
Themenstarter answered:
Re: HeatBed power cable broken

hey Manuel,

the cables I used are something like this http://www.ebay.de/itm/6-0-mm-qmm-Silikonlitze-Silikonkabel-1m-Made-in-Germany-Grundpreis-3-90-m-/151302042944 they are silicon cables, just see that they are thick enough to be used with the current U need.

happy printing
Serge

Veröffentlicht : 02/10/2016 4:10 pm
David T.
(@david-t)
Noble Member
Re: HeatBed power cable broken

Serge, I think that 6mm2 is a bit overkill, you need something for about 12-15A. Something around 5mm2 (10AWG) should be enough. 6mm2 will work too, but more expensive and less flexible.

Veröffentlicht : 02/10/2016 4:30 pm
Linux User Group Oberschwaben
(@linux-user-group-oberschwaben)
Estimable Member
Re: HeatBed power cable broken

hey Manuel,

the cables I used are something like this http://www.ebay.de/itm/6-0-mm-qmm-Silikonlitze-Silikonkabel-1m-Made-in-Germany-Grundpreis-3-90-m-/151302042944 they are silicon cables, just see that they are thick enough to be used with the current U need.

happy printing
Serge

Hi,

Well what current do i need ? I'm in Germany and i have 250V but the PSU surely does not relay that to the heatbed. So its 12 V but how much Amps go though the cables ? What diameter should the cables have ?

Does it matter if they are silicone ones or the nes you can not bend ?

Thanks!

Veröffentlicht : 02/10/2016 5:43 pm
serge.k
(@serge-k)
Active Member
Themenstarter answered:
Re: HeatBed power cable broken

Well the Silicon cables are very flexible, and will not break if moved alot, that's why I got those.
Concerning the thickness, I just compared with the original cable I had, and chose one slightly thicker. Works fine here.

Serge

Veröffentlicht : 02/10/2016 6:36 pm
serge.k
(@serge-k)
Active Member
Themenstarter answered:
Re: HeatBed power cable broken

Hi Serge

looking on that picture maybe a small second thing to fix:
The resistor R1 seems to have suffered a bit as well. Maybe if you have the soldiers iron hot it might be a good Idea to fix / replace that one as well?

All the Best
Frank

Hello again,
back with an update,... it seems U where right after all Frank.s the Resistor R1 did take a hit, ...
It actually worked well for the first prints, then I started to notice some wierd temp fluctuations appearing on a print yesterday. I investigated and found after lifting the cover that the Resistor had "disapeared" it probably detached its self due to the printed cover or whatever.... anyways it's nowhere to be found, so I need to get a new one.
Anyone know the exact specs of that part? if I reference the pic I took, it says only 102 on the resistor its self, then on the board there's marked R1 1k.
So would the denomination be resistor "R1 1k 102" ?
Thanx ,

serge

Veröffentlicht : 11/10/2016 1:15 pm
PJR
 PJR
(@pjr)
Antient Member Moderator
Re: HeatBed power cable broken

Serge

102 = 1KOhm so that is exactly the requirement (1 0 and 2 zeros = 1 0 00)

Peter

Please note: I do not have any affiliation with Prusa Research. Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage…

Veröffentlicht : 11/10/2016 2:57 pm
serge.k
(@serge-k)
Active Member
Themenstarter answered:
Re: HeatBed power cable broken

Serge

102 = 1KOhm so that is exactly the requirement (1 0 and 2 zeros = 1 0 00)

Peter

Cool, so that's part of the info I needed aparently, I still need the smd size the guy at the shop says,
here's a size chart,
I'm guessing it must be the 1005 or 1608,... can you confirm this ?

thank you
Serge

Veröffentlicht : 11/10/2016 3:30 pm
PJR
 PJR
(@pjr)
Antient Member Moderator
Re: HeatBed power cable broken

Serge

More likely to be the 2012; measure between the solder pads and anything that fits should be OK. Power dissipation needs to be greater than 0.1 Watt.

Peter

Please note: I do not have any affiliation with Prusa Research. Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage…

Veröffentlicht : 11/10/2016 5:31 pm
serge.k
(@serge-k)
Active Member
Themenstarter answered:
Re: HeatBed power cable broken

Serge

More likely to be the 2012; measure between the solder pads and anything that fits should be OK. Power dissipation needs to be greater than 0.1 Watt.

Peter

Thanx a lot Peter, that was all I needed for the guy at the shop to know what I wanted, now I only need to figure out how to convince him to sell me 2 or 3 of those and not a batch of 1000... like he wanted to 😛

if I do not succeed in this or I don't manage to re-solder a new one, is there a way to buy a new MK42 heatbed? I didn't see it listed in the parts shop ....

Thanx again,
Serge K.

Veröffentlicht : 11/10/2016 9:25 pm
PJR
 PJR
(@pjr)
Antient Member Moderator
Re: HeatBed power cable broken

Serge

You don't actually need a surface mount resistor, any resistor will do in the range 820 to 1500 ohms, with the dissipation mentioned previously.

Peter

Please note: I do not have any affiliation with Prusa Research. Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage…

Veröffentlicht : 11/10/2016 9:44 pm
serge.k
(@serge-k)
Active Member
Themenstarter answered:
Re: HeatBed power cable broken

Hello Peter just wanted to let you know that the problem is fixed.
I didn't manage to find a SMD resistor as specified, so got a conventional one with the same specs, was a little creative as of how to place it, and so it ended up below the heatbed, but I think it's more solid than before actually:-) and it seems to work, so not to bad for a total electronics rookie ... ( I guess 😛 )

pic to show of our work 🙂

https://1drv.ms/i/s!AmhL7B0FeTgNgusUUSmZxU2LmR3Ujg

Veröffentlicht : 27/10/2016 12:27 am
PJR
 PJR
(@pjr)
Antient Member Moderator
Re: HeatBed power cable broken

Brilliant!. Nice solder joints...

Peter

Please note: I do not have any affiliation with Prusa Research. Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage…

Veröffentlicht : 27/10/2016 9:41 am
Marc
 Marc
(@marc-9)
Estimable Member
Re: HeatBed power cable broken

From what I see on the pictures you also should solder the left pin (view from back) of the LED. On the first picture I can see that the resistor and LED are not soldered on the left hand side. This is still the case with the LED on the second picture.

Veröffentlicht : 03/11/2016 11:49 am
serge.k
(@serge-k)
Active Member
Themenstarter answered:
Re: HeatBed power cable broken

From what I see on the pictures you also should solder the left pin (view from back) of the LED. On the first picture I can see that the resistor and LED are not soldered on the left hand side. This is still the case with the LED on the second picture.

Hello Marc, 🙂 (wierd coincidence, my colleague who helps me soldering etc is also called Marc)

we also were quite lost as to why the LED was only soldered on one side, but thought it was meant to be that way cos the contact on the heatbed is not free (U don't see copper to solder to, only insulation coating on the board side) and it does work while printing.

Also the left side of the resistor had the same wierd coating on the left solder spot, we did remove some of it before putting the new resistor on, and again it seems to work now ...

so now I'm eaven more confused,... what do U think about this Peter?
do U maybe have a reference pic to show us how it's supposed to look ?

pic to show that it is working atm...
https://1drv.ms/i/s!AmhL7B0FeTgNgvdNj_aGW0W7kBURkA

thanx and happy printing 🙂
Serge

Veröffentlicht : 05/11/2016 10:07 pm
PJR
 PJR
(@pjr)
Antient Member Moderator
Re: HeatBed power cable broken

Serge

The key here is that it's working. Leave it alone; if it stops working in the future, then you fix it. If it's not broken don't fix it.

These boards are wave soldered (or reworked with solder paste and heat gun) with a lacquer coating, so there is likely to be a soldered connection underneath the LED connector.

Peter

Please note: I do not have any affiliation with Prusa Research. Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage…

Veröffentlicht : 05/11/2016 10:53 pm
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