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USB Power Supply Contacts

Discussion in 'Audio' started by argon, Jun 24, 2020.

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  1. argon

    argon

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    Apr 14, 2016
    NB: I joined here a few years ago when I had a guitar electronics-related question. I know nothing.

    I have a small bluetooth speaker. The female connector broke free (was only hot-glued in place) and I'd like to secure it back into place. It has five (5) small finger extensions that bend downward to make respective contacts on five small contact areas on the printed circuit board. I've tried to be careful not to bend any of these, leaving the ones that are supposed to be in contact in their downward positions. This USB connection supplies only power; there is no data transfer whatsoever.

    As you can see on the attached photo, I've numbered those "fingers" and you can see how they line up with their respective circuit board contacts. I believe that (as I've numbered them) fingers #3 and #4 are the ones that, when making contact, will provide the correct connections. Would someone confirm or correct my assumption? Thanks.
    IMG_3454a.JPG
     
  2. dave9

    dave9

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    Mar 5, 2017
    5 pin micro-B uses pin 1 for 5VDC (aka VCC) and pin 5 for ground, but I suspect that you have your pins numbered backwards and what you show as pin 1 is really pin 5 and vice-versa. Either way, those two pins are what you need. This is standard for USB, to have power and ground at opposite ends.

    Not only does it look that way from the PCB layout (where a ground plane would be around the edge rather than towards the middle of the PCB, but also because it has connection traces for (your labeled as #3 and #4 which are really pins #2 and #3, which are traditionally used for #2 D- and #3, D+ (D as in data), with (your labled #2 actually being #4) going unused except for implementations of OTG ID function on devices that support that.

    Anyway, I question whether your device may also have some data transmission functionality due to those D+/- pins going somewhere, but that you don't need them in the case of only needing power to run or charge. My point is that I'd still solder them to the pads as they were in the first place.

    Back to the failure itself, didn't the connector have tabs that were soldered to pads on the PCB or slots that tabs sat in? Hot glue alone would be a very poor way to try to secure that. If you can get it clean enough, I might try laying a bead of epoxy along both sides, but also having a greased USB plug inserted into it, to make sure that not only does no excess epoxy get in, but also greased to ensure that the epoxy does not cause the plug to be permanently connected, then after the epoxy has set, you can pull the plug out and use electrical cleaner to get the grease off the plug and out of the socket.... or just be very careful using epoxy and skip that step entirely, but sometimes epoxy wicks and goes where you didn't intend for it to go, especially with thin metal shell sockets that have gaps in them.
     
    Last edited: Jun 24, 2020
    argon and Martaine2005 like this.
  3. davenn

    davenn Moderator

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    Sep 5, 2009
    Looking at all the corrosion everywhere, me thinks you have a much bigger problem that identifying USB pin-outs !! ;)
     
    argon likes this.
  4. dave9

    dave9

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    Mar 5, 2017
    At first I was wondering, how the heck did that connector pull off and leave the pads intact on the PCB, but now that I look at it again, the pads look ripped completely off.

    SO, use an x-acto knife or similar, to scrape off the coating a few millimeters back from the edge of the torn copper for (at least pins #1 & 5) till you get shiny copper, and solder a piece of jumper wire there to bridge over to the USB socket pins. After this is complete, clean and put epoxy over at least the torn edge of the copper pad, otherwise with time it may oxidize and further delaminate off the PCB.

    On the other hand, what I would be tempted to do instead because I HATE PCB mount micro-USB for its fragility, is put a standard panel mount, DC barrel socket on the housing and a mating DC barrel plug on the charger, then air wired to the respective +/- power input copper after the torn areas.

    That would be much more robust, (if you pick a high quality major brand socket) though you then lose the universal USB charger aspect of it. There might be some seller on ebay that makes a micro-USB to DC barrel adapter widget. Something like this:
    https://www.ebay.com/itm/DC-5-5x2-1...nnector-Adapter-Charge-Converter/254021988958

    Or maybe another seller who can get it to you in a month or less.
     
    Last edited: Jun 25, 2020
  5. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    Funny how opposing the attitude towards barrel connectors can be :)
    That would be my favorite to preserve the look of the device and re-use the existing USB power supply without further modification.
     
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  6. argon

    argon

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    Apr 14, 2016
    Re: corrosion... Yeah, I plan to use a pencil eraser to gently "clean" all contacts. But, I had a good laugh (at myself, I guess).

    It's been a while since this thing broke, and I forgot the manner of socket attachment to the PCB; I guess the hot glue mention was an idea I previously had. Just above the opening for the socket you can see white debris on the plastic just above the opening -- this is from a brief attempt to glue a support, but I chickened out and removed my work immediately, not being sure of the contacts (hence, this thread).

    I've taken a few more photos to give a better perspective of this situation and components. No need for a lot of description; all is obvious, especially the failed spot-welded attachments on both the socket and the PCB. Yes, this attachment method is terrible for a component that necessarily gets a lot of use (abuse).

    Now that I know what the exact contacts should be, I'll be reattaching the socket, most likely using a small block of plastic, gluing it to both the vertical plastic casing and the horizontal socket surface together.

    This bluetooth speaker is pretty niffty; no longer made; pretty small -- fits in a pocket, but has surprisingly good overall sound quality. So, I'd like to salvage it. Thanks, all, for your comments. 1. Control panel.JPG 2. Circuit board.JPG 3. USB socket.JPG 4. Failed attachements.JPG

    PS - Dave9 and Harald - Your suggested fix is way beyond my capability, and soldering equipment. I worry about frying a big cap or resistor on my guitars. I can just see me melting a hole through the board! Thanks, but I'll try repositioning first, using an overkill gluing technique. I'll be sure to follow up with a photo or two.
     
    Last edited: Jun 25, 2020
  7. dave9

    dave9

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    Mar 5, 2017
    Yes I've faced the same frustration with the multitude of barrel connector sizes, and even worse in rare cases when a manufacturer decides they're going to make positive power the outer barrel plug sleeve. At the same time, it beats having a broken connector and I can swap a different barrel plug onto an AC/DC adapter cord much faster and easier than this microsurgery involved in repairing a broken micro USB socket, or there are now $2 adapters on ebay, even less expensive per piece to get a kit with different sizes.

    They just shrunk the micro and now USB-C size too much, saving a few millimeters to build disposable widgets. I'd prefer they used full sized USB-B on anything large enough that it'll reasonably fit, which is just about everything besides cellphones, cameras, and far fewer numbers of random devices.

    It's even less excusable for micro HDMI, where practically nothing using it couldn't fit a full sized HDMI socket. At least in the case of mHDMI, devices are typically less subject to movement or other socket stresses.
     
    Last edited: Jun 25, 2020
    argon likes this.
  8. argon

    argon

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    Apr 14, 2016
    Question: Re: The two relatively large, square metal spots on the PCB to which the two tabs of the socket were spot-welded...

    When spot-welded to the PCB, do these welded socket-to-PCB connections, in addition to physically attaching the socket to the PCB, typically provide any circuitry, i.e., grounding? MUST the attachment tabs of the socket make contact with the contact/welded areas of the PCB?? I can't readily access the other side of the PCB to see if there are leads coming off these attachment areas.

    It occurred to me, having posted here and now thinking more critically about this and examining the photos, is that there is/was no need to determine which finger-like connectors should make contact with the PCB contacts -- just ensure that all are making their respective contacts; which ever contacts required by the connected external device for power and any IO operations will be utilized. If you look at the photo of the underside of the socket, you can see that the ends of all the finger-like projections are discolored, the same color as the electrical contact areas on the the PCB.
     
  9. dave9

    dave9

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    Mar 5, 2017
    No you don't have to connect the shell to those ground pads. With a shielded cable it might provide longer transmission distances for data, but you're not using data. More critical was that this is the only way the socket was mechanically attached, the weak link and why it comes off fairly easily from stress.

    The undersides are discolored because as I noted previously, it ripped the copper off the board and that copper is now still soldered to the pins. You need to desolder that and have fairly clean pins. A quick wipe with a soldering iron is all it usually takes.

    When you previously wrote that what I'd described, to scrape and solder a jumper wire, is beyond your capabilities (if that is what you meant?), that is not really optional but rather required because the copper is torn off the board. You can't just solder the pins back down onto the board as they were with no further effort, without the copper there for solder to adhere to, and electrically conduct to the torn area after the solder pad.

    Well, in theory you could "maybe" scrape the coating off right at the edge of the tear and bridge the gap to the pins with solder alone, but that's a really ugly way to do it and probably harder than using scraps of bare wire instead, and would make it all the more important to coat that edge with epoxy (or something, even hot glue) to keep oxygen from getting to the exposed copper that's lifted still at the tear.
     
    Last edited: Jun 26, 2020
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  10. argon

    argon

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    Apr 14, 2016
    Thanks, dave9. I can barely imagine soldering something so small -- I can envision my 20w Radio Shack iron just melting two or three of those thin finger projections at a single try; I think the tip's diameter is the width of two of those projections. Well, I'll re-read this thread a few times and figure out how to accomplish the necessary tasks. Thanks.

    PS - If this socket were the size of the old computer serial or parallel connectors, this would be easy. I guess there must be micro-sized solder and soldering equipment....
     
  11. dave9

    dave9

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    Mar 5, 2017
    If your Radio Shack iron is the cheap type that has a screw in *nail* type of tip (which uses nickel plating over a copper core), it might help a bit to file, grind, or sand either a flat or sharper point on it, as solder can erode that type of tip away to a concave surface that is difficult to use, as is old exposed copper that has oxidized and conducts heat poorly as well as poor solder adhesion.

    Otherwise, it's mostly in the technique. If you wanted to forget about the data pins and just do the two outer pins, you could even clip (or bend back and forth until they break) the data pins off to give you more working room, but leaving them in place you would just start in the middle and work your way out, heating the pin and touching thin diameter solder to the pin to flow it. It may be more difficult with this tiny connector socket that is held together by plastic, in that case you might want to put the soldering iron on the jumper wire and flow the solder from that to the connector pin.

    The best use of your big crude soldering iron tip would be to use soldering paste, then you just align the pins to the jumper wires, smother the area with the solder paste, then when you heat it, the metal in the solder paste moves as it melts, then clings to the pins and you don't have excess solder causing solder bridges. Granted that is much easier to do using intact solder pads rather than a jumper wire touching the pins. For now if you can acquire some desoldering braid, then if you end up with bridged connections you can just wick the excess solder away, remembering that you have precious few seconds to work with before the plastic in that tiny USB socket melts and is ruined.

    Keeping this in mind, I refer back to my idea about getting a panel mount barrel socket and using that instead of a PCB mounted mUSB socket, then putting a mating plug on a charger if you don't already have one that's regulated 5VDC with a barrel plug already on it to guide you in what size barrel socket to acquire to match it.

    Then again if you are expecting to do more electronics work in the future, eventually you'll have to hone your small soldering skills and move up to a soldering iron with different tips, and learn some techniques for gluing down copper foil or just take a piece of copper wire, on a hard flat surface, and hit it with a hammer until it's flat and thin, then you have a piece of thick copper foil to glue down where the pad was.
     
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  12. argon

    argon

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    Apr 14, 2016
    Thank you for your in-depth reply -- lots of good information and ideas to consider.

    Actually, my 20w is my small iron, which is too small (heats too slowly) for most guitar work, but I imagine it would be plenty enough for these fragile connectors. (I use my 40w Radio Shack iron for guitar work -- pots, resistors and caps; I need those 40 watts to heat the back of a pot to attach a ground wire.) But, I think I will be doing more soldering in the future--not just this project (more guitar stuff) and so perhaps I should pause here--as you seem to suggest-- and buy a good, versatile soldering kit. A lot of guitarists like one by Weller (I'd have to search for the most popular model). I do have flux, paste for tinning my tips, and de-soldering braid (I could never get the suction bulb to work for me). I'm in no rush to repair this speaker; acquiring the proper equipment will only enhance my success.

    I'll be using your ideas, but having thought as I wrote this, yes, it's time to pause and get that new soldering kit. If you have a suggestion, please offer it. I think the Weller irons are of a pistol grip design, and for me, probably will not offer the greater eye-hand control that a pencil grip type would offer. But then again, with the gun type you could rest the butt of the grip on a table to steady the soldering gun, and simply lean/rotate the soldering tip down to make a precise contact.... Nah, I'm pretty sure I need a pencil grip iron. (Well, those Radio Shack irons are the only ones I've ever used, resting my forearms/wrists on the table edge to steady my hands.)

    Anyway, thanks for all this info.
     
  13. dave9

    dave9

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    Mar 5, 2017
    The guns are more for larger electrical work, like use a butcher knife to cut the steak on your plate as you eat it.

    Best value bet is pencil style on a temperature controlled solder station from a major brand like Weller or Hakko, which are roughly $100. You can still get by with less, there are cheap generic clones of older Hakko models which are quite usable for their ~$25, and take Hakko and Hakko clone tips so there is a wide assortment available, like a "936 soldering station" on ebay, or there are some wand-only soldering irons that take the hakko style cylinder w/iron tips that are easier to use than the Radio Shack. It's an entire topic onto itself, what soldering iron or station for what purposes and budget, but a pistol style is not very good for electronics work.
     
  14. argon

    argon

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    Apr 14, 2016
    I've started to look a little. I'll try to find a thread or two on this site. So far, the second one on this "best of" evaluation looks overall pretty good: X-Tronic Model #3020-XTS-ST. Comes with 5 tips, good power. Link:

    https://www.electronicshub.org/soldering-stations/

    No rush -- I'm going to look around. Thanks.
     
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