Lint – the unseen foe

I’ve seen this a few times and it’s always surprised me until I’ve figured it out. Hopefully this brief post helps someone else one day.

Years ago a friend of mine had me over to help take his phone apart. The headphone jack had stopped being reliable (yeah, way back in the day when it was normal for you to plug in headphones). We had fun taking the phone apart, but in the end it turned out that the headphone jack was jammed full of pocket lint. Yup. Some careful digging with a pin and tweezers and we cleared out an alarming amount of lint that had jammed up the port. This fully restored the headphone jack function.

One of my kids had the same thing happen to them. Janky headphone jack, and yup – the bottom was stuffed full with pocket lint. Just be very careful poking around in the port. It’s not very big and you can mess stuff up. Lint is soft and will come out with some gently coaxing.

Lately my ~1.5yr old Pixel 4a had stopped reliably charging. The USB-C cable would fit in fine, but not stay put. It would also pop out very easily. This morning after another failed to charge overnight incident I again inspected the USB-C port. It looked fine. Probing very gently with a pin, it soon became obvious there was some lint in there. Then I pulled out more and more.. an alarming amount. There was a lot of lint. Now I can look into the port and see the shiny plastic bottom, not a dark matted blackness. The USB-C cable seats nice and deeply and doesn’t pop out easily.

Given phones probably live a good percentage of their lives in your pocket, this isn’t a surprising outcome. Still – cleaning out lint wasn’t even close to the first thing I thought of doing in any of these cases. I’d even checked what my warranty and repair options were. The fix was 2 minutes of careful work.

Samsung Galaxy S7 Battery Swap

Sure, the Samsung S7 is a 6 year old phone at this point – but it’s perfect for my son who’s in grade 7 and doesn’t really need a phone. The other day it stopped turning on – when you plugged it in, it would indicate the battery was at 100%. I could even get it to power on while plugged in, but removing the USB power would result in an immediate black screen as it powered off hard.

I sort of dreaded opening this phone up because it’s one of the ones that is glued shut. I was pleasantly surprised, as a little heating with the heat gun and the all metal back came up pretty easily using a suction cup. After that there were some phillips screws to remove and I was able to see the battery.

It was clear there was a problem here – the connector should be squared up with the rest of the circuit board. If you look closely – you can see that the battery has also shifted down significantly within the phone, nearly 2mm.

Taking a close look at the cable – you can see the connector is a little busted up despite my photo being a bit out of focus.

I attempted to reconnect the cable, but soon found out that the connector was badly damaged and it snapped off the cable completely.

Oh well. Off to search up buying a new battery for this phone. A quick look around and it seems there are lots of choices – some as low as $16 (eBay), and the normal crazy mark-up ones at $60-$90. I opted for one of the Chinese made knock off brands off of Amazon that came with tools (junk) and the adhesive to re-attach the back. It also claimed to be 3300 mAh vs the stock 3000. It was at a slight premium vs. eBay, but only a couple of bucks and the reviews were good. Worth the $25 and it shipped to me the next day.

My pricing logic for stuff like this is to avoid the cheapest prices – these are often very cheap for a reason. There is a step up from the cheapest where you’re going to get basically the same part up to the next price plateau – if you can discern the price notches you can basically buy at certain quality levels. The danger with all of these is that lots of unethical sellers will slap OEM labels on parts that are not, so often paying a high premium is not buying quality at all. It’s always a gamble which is frustrating.

The battery I’m replacing was already previously replaced. I think this is why the battery didn’t fit very well in the phone.  The poor fit is likely what resulted in it breaking off (when the phone was dropped, probably multiple times if I know my son). If you fit the broken battery into the compartment properly there is a significant gap at the bottom.

Again, this is nearly 2mm gap. The OEM battery is tape/glued in – but I suspect it also fit much more snugly in the space. If you are replacing a battery – consider if it will slide around and either tape – or pad it – to avoid the battery moving. I know that I’ve done battery swaps and left a gap in the past – I probably won’t in the future.

The new battery fits like a glove. Top to bottom, almost no space to move around. So I didn’t bother taping it in place, I’m pretty confident it’ll stay put.

While I’m not a fan of glued shut phones – I did use adhesive to re-seal the phone. Hopefully I won’t have to go back in at all. In a couple of years this phone will basically be too old to use. While it’s still running stock firmware, it does appear that there is an unofficial but current LineageOS build for it.

The S7 got a 3/10 score for repairability – but it wasn’t really that bad to get at the battery. The places where it got hit on the score was replacing some of the other components – I’ve certainly had more than 1 USB charge port go bad, and gluing that to the screen seems like a really bad idea. There really needs to be a better trade of for waterproofing and repairability.

Consumer Electronics and Leaky Batteries

Recently I’ve been working on some IR remote control stuff, this has me digging through my bin of old remotes looking for one I could use as the controller.

I had one of these classic Haupauge remotes which I’d used a long time ago with a MythTV setup. I’ve long ago retired this machine and tossed the remote into the bin. Sadly I didn’t remove the batteries, and when I opened up the battery compartment I saw that they had leaked and corroded.

This has happened to me before, and usually cleaning out the battery compartment and putting some new batteries is all that’s needed. Unfortunately not this time.

It turns out that opening this remote is easy enough, but I needed some force. The top part snaps onto the lower part – no screws. I used a metal blade to get the two parts separated a little and then was able to get a pry tool in to pop them apart. The case was surprisingly durable and it did need more force than I was comfortable using – but in this case, I figured it didn’t work so I had little to lose.

Here you can see the circuit board before I’d cleaned it up. There was quite a bit of white build-up around the chip and generally around the circuit board at the bottom. There was a recent hackaday post on restoring an old gameboy that had similar problems.

Unfortunately I was not as lucky with this remote.

The chip lost an entirely leg – and this is the power pin as well. I suppose if I was highly motivated to repair I could try grinding off the corner of the chip and then soldering a bridge inside. However, this is a bit beyond my ability to work at microscopic levels.

The lesson here is that when you stash an old remote control away – remove the batteries. For me, the remote is junk – I might strip out the IR led and re-use it somewhere, but that’s about it.