MiSTer FPGA Forum

Long story short, the micro USB on my mister has never been great, and I think it's reached the point of unusable (despite everything being hot-glued and wiggle-free in my case). From what I've gathered during my research, there is no other way to get USB via GPIO pins or the like. Rather than spend money on getting a new mainboard which are impossible to find anyway, I thought I'd try to solder the USB OTG cable directly to the USB contacts.

However... while I can do some basic soldering, this is by far the most delicate soldering job I've ever undertaken. Those pins are tiny, and while the port itself is through-hole, it looks like the pins might be a surface mount? I've done some basic research, and ordered some 26 AWG solid wire, a super-fine tip for my old Weller, and a flux pen. I'm looking for any tips people are willing to give me on how to not screw this up, but specifically:

1. Is this even a good idea? Is there some better method I've overlooked?
2. It looks like I'll need to remove the USB port to access the contacts. Are the pins themselves surface mount, or is there some weird shenanigans going one where they attach somewhere in the silicon sandwich?
3. Am I an idiot? Is this even possible with human hands?

Thanks in advance for any info that increases my slim chance of success.

You can do it! Soldering is the solution to everything. If you are unsure about soldering surface mount check out GadgetUK on youtube. he has tons of soldering repairs. Flux is your friend for sure. Go slow, it's good you are using a decent iron as opposed to charging in with a 12 quid job from ebay.

If your eyes are going like mine, spend about 15 quid on Amazon for a head magnifier. I'd also practice a little before going straight in. Find an ol clock radio or something and unsolder/solder a few bits that don't matter.

Is replacing the port not an option? Or even reflowing the existing solder?

I totally did this and took the opportunity to wired in a power button too. Flux is key in my experience. I removed the micro usb port on the DE10 under it the pad are surface mount but they are large enough to do pretty easily. On the USB hub there are through holes you can solder pins into and use a 4 pin connector to make it easier to remove. If i get a chance I'll take mine out of the case and send attach some pictures.

RascalUK wrote: ↑Wed Mar 16, 2022 2:06 pm You can do it! Soldering is the solution to everything. If you are unsure about soldering surface mount check out GadgetUK on youtube. he has tons of soldering repairs. Flux is your friend for sure. Go slow, it's good you are using a decent iron as opposed to charging in with a 12 quid job from ebay.

If your eyes are going like mine, spend about 15 quid on Amazon for a head magnifier. I'd also practice a little before going straight in. Find an ol clock radio or something and unsolder/solder a few bits that don't matter.

Is replacing the port not an option? Or even reflowing the existing solder?

Excellent idea about practicing on some junk first, and the magnifier. Just ordered one, and I'm sure that will help a lot.

In theory, replacing the port could be an option but sounds harder to me. Also, I have plenty of USB cables to chop up and use for this purpose, where I'd have to special order whatever part is used on the DE10. As for reflowing it, I don't have an over or a heat gun that I'd be comfortable using and generally that scares me a bit anyway as I don't want to cook the chips if I don't have to. I suppose I could attempt to touch the soldering gun to the pads in an attempt to fix any cracks... If that's what you meant, that is a good idea too. I'll try that first, assuming I can even get the tip in there, and that's a big if.

espo83 wrote: ↑Wed Mar 16, 2022 2:22 pm I totally did this and took the opportunity to wired in a power button too. Flux is key in my experience. I removed the micro usb port on the DE10 under it the pad are surface mount but they are large enough to do pretty easily. On the USB hub there are through holes you can solder pins into and use a 4 pin connector to make it easier to remove. If i get a chance I'll take mine out of the case and send attach some pictures.

Thank you! The fact you've done this before makes me feel better; I know it's at least possible!

Yeah I actually meant with the iron rather than a heat gun. I only have a cheap heat gun and never truly trust the temps.. I'd be inclined to douse it in flux and flick the iron over it if you can get at it. It's prob failing from cracked joints from stress, bound to be a mechanical problem I'd bet.

If you do go the wire soldering route, take some pics too, I'd like to see it as might even have a crack myself in an effort to future proof it a bit. Watch you get the right wires to the right pad though with no bridging, sounds like it will be tight.

Here's the USB board Data coming down from the DE10Nano to the header and power going to the underside of the board to the barrel connector


Then on the DE10 Nano the micro usb port has been de-soldered and the data lines soldered. A new barrel connector installed (you can see it in the upper left) that goes to a push button (its in the lower right) and to DE10 power and the USB hub power. I plug the adapter that came with the DE10Nano into this barrel connector and everything is operated by the one button.

RascalUK wrote: ↑Wed Mar 16, 2022 4:21 pm Yeah I actually meant with the iron rather than a heat gun. I only have a cheap heat gun and never truly trust the temps.. I'd be inclined to douse it in flux and flick the iron over it if you can get at it. It's prob failing from cracked joints from stress, bound to be a mechanical problem I'd bet.

I did this last night and initial tests are great! I didn't use flux though... I don't understand the purpose of it in this case. I mean that literally, BTW... I'll trust you that I should have but didn't know until I reread this. Why should I have used it?

Flux is used to clean/prepare the surface that is going to get soldered so it will create a nice bond. If your solder wire contains a flux core, as a good portion of them do, then you don't really need to add any yourself.

In my, limited experience, flux helps solder flow better and stick where I want it to stick. When I'm soldering small contacts that are close together it helps to prevent a solder bridge between them. It may not needed but It has helped me.

Here's an example,
https://www.youtube.com/watch?v=9SboSxxRpfY

Yeah for the reasons described by espo83 above. It just tends to make the solder go where you'd ideally like it to go

Sorry all, I didn't phrase my question well. I know flux is great when you're trying to solder two things together, but in this case I was just reflowing existing solder on existing connections. I was still advised to douse it in flux which I didn't understand. But I know I'm ignorant of a lot of things in electronics, so I'm just looking to learn.

Flux cleans oxidation off the solder and the contact points, which allows for better solder flow and better mechanical and electrical bonds. Metal oxidizes quickly when heated, which can lead to crusty, brittle, unreliable joints if there isn't enough flux. Sometimes you won't be able to get solder to stick at all if there isn't enough flux. That's why flux is useful when making new connections *and* when re-flowing old connections. Both situations require clean surfaces, good solder flow, and good bonds.

This is my favorite video on the topic: https://www.youtube.com/watch?v=tfIwHuGzUEk

The video doesn't get into the science behind it, but it very clearly demonstrates what good and bad joints look like, how flux helps in the creation of clean solder joints, and how joint quality decreases if you don't use flux or as your flux gets used up during re-work. This is why you'll see people regularly adding more flux as they work on stuff.

Obviously flux can be a pain to clean up (and the residue can be potentially corrosive and/or conductive depending on what kind you use) so you don't want to use *too* much, but you'll learn how much to apply and how often to re-apply through experience.