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Power Supply Connection Issue

Posted by jamestay 
Power Supply Connection Issue
November 30, 2012 05:36PM
I bought a sanguinololu board a while ago as I am designing and making a 3D printer for a school project.
I am starting to think this may have been too ambitious as I don't have much electronics experience.
I originally was going to use a PC power supply but changed my mind and bought an AC-DC Switching Power Supply on eBay.
I swapped the power connector for a screw terminal and connected everything up/powered on.
The LED on the board came on and I can use pronterface to check the bed/tip temperature. I have a Sanguinololu kit which is also working.
But I can't do anything with the other side of the board (e.g. make the motors move). I then saw the power supply had stopped working (it had a green LED inside which had been on but is now off). I can't seem to get any action out of the power supply now.

The only thing I can think is that I soldered the screw terminal on badly as it seems not completely rigid but I don't see how this would damage the power supply.

Any ideas why the power supply has/seems to have stopped working?

Also what it the correct method of soldering in the screw terminal?

Thanks in advance smiling smiley
Re: Power Supply Connection Issue
November 30, 2012 06:41PM
An over-current issue is one likely cause. Does the power supply have some sort of inline over-current protection, like a resettable circuit breaker or a fuse?

If you encountered an over-current situation (short circuit or simply too much draw for the supply) IFF there is a fuse it may have blown. If a circuit breaker, it may have tripped. For the fuse replace as necessary. For the circuit breaker, reset it.

If you have a sustained short circuit condition (crossed wires, solder bridge, etc.), regardless of the protection scheme, the supply will fail to work correctly until it is resolved.
Re: Power Supply Connection Issue
December 02, 2012 12:19PM
Thanks for replying.
It has an in-line fuse, but having taken the cover off I think there might be a different problem. There is some kind of white goo (silicon?) which looks like it has come out of the ferrite ring. Don't know if this could be causing a problem?

Because I tried changing the connection from ATX to screw terminals in a rush there are a few other problems I might have created.
I have attached some pictures but basically I couldn't get the solder out of the holes for the screw terminal and ended up magling them to do so. Is it rescuable?
Also I just left the ATX headers in because I assumed they wouldn't affect the circuit but maybe this was a bad thing to do as well... oops.

open | download - IMG_0002.JPG (427.6 KB)
open | download - IMG_0003.JPG (443 KB)
Re: Power Supply Connection Issue
December 02, 2012 12:49PM
The goo is just glue that they like to use in cheap electronics.

Looks like you may have created a short when you mangled the power input on the board. Does the power supply work when not hooked up to the Sanguinololu?

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Re: Power Supply Connection Issue
December 02, 2012 12:51PM
I'm not sure what's going on with that first picture. I'll admit I've never seen that. It sorta looks like something overheated and melted, more like what sometimes happens to a transformer than a simple ferrite. On second look...It actually looks like something got spilled during or after fabrication rather than damage. Is the "goo" hard (literally or pliable but solid) or liquid (flows, whether plastic flow or more liquidy)? If an adhesive, then whomever produced the board is a shoddy mfg and should be avoided in the future. They used way, way too much.

The second pic, showing the damage to the PCB....fixable? Possibly. I'm not sure how many layers were used to design the board, but if it's 2-layer, the fix should be relatively straight forward. If multilayer (ie, 4 layer like is claimed for some designs) it could be a bit more difficult. Your image doesn't give me enough info to make recommendations though, aside from recommending that you purchase a small reel of wire-wrap wire (silvered, solid-core, 30ga insulated wire) to bridge the failed connections. Sometimes the replacement component has to be modified to ensure a solid fix, somtimes it can be done by inserting the new component and doing the repair from the other side of the board. As said before, image doesn't show quite enough info...

In the future, when you make mods like this, I'd remove the component in a way that does not affect the PCB itself FIRST, then carefully de-solder each pin. Finally use a solder sucker or de-soldering braid to remove solder from the holes, then clean up as necessary with a fine drill bit of the appropriate size and use q-tips or similar with rubbing alcohol to remove the lingering rosins leftover from the solder. ALWAYS remember that the board is your weak link. Connectors and components can always be replaced...(same goes, btw, when replacing ICs. snip the pins, then and only then de-solder the pins from the board. It almost guarantees reduced or eliminated damage to the substrate (PCB and PCB traces), whereas attempting to remove a component with an eye to re-use of the offending component is often a recipe for PCB damage.

Edited 2 time(s). Last edit at 12/02/2012 12:53PM by xiando.
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