stepdown converter is giving me ****

PCB problems and fixes
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ChurchOfSolipsism
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stepdown converter is giving me ****

Post by ChurchOfSolipsism » January 12th, 2016, 8:33 pm

So I live in Germany (where we have 230V), which is why I got this stepdown converter for my Egret 3:

http://www.amazon.de/Lianlong-LLD300DT- ... s=Lianlong
(sorry, couldn't find an English source)

Worked flawlessly for a couple of years, then stopped working about a year ago. Today I check out the fuse, my ampere meter says the resistance is infinite (as you can probably see I know next to nothing about electronics components - this is probably how a fuse is supposed to behave?), but when I put it back into the converter, the light behind the switch comes on. At this point I'M feeling intense joy since I'm a stingy ****, I plug in the Egret 3, switch it on, nothing happens, and I see that the light on the converter has gone out again. Whatever I do, I can't get it to work again.

What do you guys think - should I just get a new stepdown converter or is there some hope left? Pretty short on cash right now but would like to play with my EGret 3 asap again...

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Re: stepdown converter is giving me ****

Post by Eddhorse » January 12th, 2016, 11:26 pm

I guess you will have to check the voltage going into the stepdown (any pics?)
Also check the voltage going out to the monitor,

Is there another power supply or PC also?

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Re: stepdown converter is giving me ****

Post by kernow » January 12th, 2016, 11:40 pm

Borrow someone's to check?

But yeah a multimeter is all that's needed.
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Re: stepdown converter is giving me ****

Post by baddy » January 12th, 2016, 11:40 pm

Fuses have very low resistance, ideally 0 as it's just a thin wire. You might want to change it. Check the fuse itself, you can see if it is okay (if there's a line going to both ends it's fine, if it's burnt it's not).

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Re: stepdown converter is giving me ****

Post by ChurchOfSolipsism » January 13th, 2016, 12:38 pm

baddy wrote:Fuses have very low resistance, ideally 0 as it's just a thin wire.
Wouldn't that mean that its resistance is higher than if it was a thick wire? SOrry for the stupid questions...


Thanks guys, I'll do what you've suggested and report back.

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Re: stepdown converter is giving me ****

Post by ChurchOfSolipsism » January 13th, 2016, 1:15 pm

Right, according to my multimeter, the power point the stepdown converter is plugged into provides 227V. But the converter itself doesn't provide any juice at all. Nothing at all changes when I switch it on or off.

The fuse looks alright, the wire's going from one end to the other, but as I said before, when I measure its resistance it's infinite. Does it make sense to buy a new fuse? They're not expensive, but if there's a good reason for why it's pointless I won't bother...

I don't have any pictures of the stepdown converter since all my digicams are broken and I don't have a smartphone, but the link I posted contains a picture.

Do you think that opening it up even makes sense? I've done soldering before, no problem, but tinkering with PSUs and the like, well, probably not such a good idea, no?

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Re: stepdown converter is giving me ****

Post by kernow » January 13th, 2016, 1:34 pm

I'd replace the fuse definitely.
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Re: stepdown converter is giving me ****

Post by Olisan » January 13th, 2016, 2:02 pm

Specific problem on these **** chinese stepdown.
Have issues on 3/4 of them too.

You need to open the plastic part. Down, you will see a small component who is another "fuse" inside the converter. This is the part broken. You don't need to replace it. Just make a solder to skirt it.
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Re: stepdown converter is giving me ****

Post by kernow » January 13th, 2016, 3:40 pm

Hmmm hard soldering fuses?
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Re: stepdown converter is giving me ****

Post by ChurchOfSolipsism » January 13th, 2016, 3:54 pm

Yeah, maybe I'm a big sissy but I wouldn't like to see my cab **** up because I was too cheap to buy a new stepdown converter... anyway I opened the thing up, but I couldn't find the part that Olisan talked about. I made pictures with my **** laptop's cam:

Image
Image
Image
Image

As for the rest, I don't have a replacement and I don't know anyone who might lend me theirs. I think I'll get a replacement fuse and see how it goes from there...

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Re: stepdown converter is giving me ****

Post by ChurchOfSolipsism » January 13th, 2016, 4:07 pm

Ok, turns out Kernow was right: when I bridge the fuse, the converter works again. :shifty:

Thanks fellas, as usual you were quite helpful!

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Re: stepdown converter is giving me ****

Post by cools » January 13th, 2016, 4:09 pm

Kern was trying to say: hard soldering fuses is an extremely bad idea.
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Re: stepdown converter is giving me ****

Post by ChurchOfSolipsism » January 13th, 2016, 4:21 pm

Yeah I was referring to that when I said I needed to get a new fuse. I don't feel comfortable about permanently bridging a fuse either, I just did it with a metal screwdriver to see if the fuse was the problem (if I wasn't so clueless I could have done that first and spared myself the trouble, but oh well...). So no worries!

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Re: stepdown converter is giving me ****

Post by Eddhorse » January 13th, 2016, 8:55 pm

Great work well done !!

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Re: stepdown converter is giving me ****

Post by PascalP » January 13th, 2016, 9:46 pm

For your info:

Infinite resistance means there is NO connection, so broken fuse!
A good fuse would read 0,.. Ohm. This is the opposite of infinite!
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Re: stepdown converter is giving me ****

Post by ChurchOfSolipsism » January 13th, 2016, 11:06 pm

Thanks mate, that's what I figured. Resistance does get higher the thinner a wire gets, and if there's no current at all something's ****. I'm not a complete idiot when it comes to electronics, but reading through the thread again I wouldn't blame anyone for thinking so... :problem:

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Re: stepdown converter is giving me ****

Post by baddy » January 14th, 2016, 9:32 am

Well said :awe:

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