"Hang on, I'm on my hamburger phone. *shakes phone*" -Juno, 2007.
An iconic line from an even more iconic movie, Juno was my main jam when it came out way back in the late '00s right as I was finishing up high school. I related so much to Juno's character: her inability to not be sarcastic, her love of sweater vests and her eclectic collection of tchotchkes. That's why when I tracked down an analog hamburger phone back in 2008 for super cheap I picked it up in a heartbeat. Despite living in an age where the landline is going out of style, I've always found a use for the phone; usually as a buzzer for whatever dwelling I was occupying at the time. That's it's current use at the moment actually: the buzzer for my apartment.
That's why I was oh so sad when I noticed one day that I could no longer hear the person at the buzzer thru the hamburger (more than likely related to an elbowing incident over the winter during a party I held). It still rang, the numpad worked since I could still unlock the door using my code and weirdly people could hear me down at the buzzer, but nothing came thru the speaker which kind of defeats the purpose of having an intercom buzzer.
I finally decided enough was enough and embarked on a repair adventure. I was apprehensive since I didn't want to break it anymore than it already was but it wasn't exactly pulling its weight in its current state. The hardest part was figuring out how to break into the hamburger. It appeared to be solid plastic with little forgiveness. My theory was that there must be a connection somewhere between the main burger and the top bun that had become loose so I knew I would have to get in somehow.
[If you prefer video to written word, you can find the video I did on this adventure here.]
The ProblemAfter struggling to separate the parts using various prying tools from the iFixit tool kit, I ended up trying another avenue by using the SIM bit for the screwdriver to push out the pin that connected the hinge of the phone, which worked quite well and showed me the problem immediately. There was in fact a wire that traveled thru a small hole in the hinge to the bun portion of the phone to connect the speaker to the rest of the phone and it was severed in half. It became apparent that the opening action of the hinge over the years had rubbed against the wire and caused it to slowly rip in half.
Now that I knew exactly what the problem was, I went back to trying to break into the hamburger portion of the phone. Again I started prying the burger portion away from the bottom bun portion. At one point I tried to see if the cheese portion with the numpad was how you accessed the insides, but no dice. Eventually I was able to separate the bottom bun from the burger by using the jimmy tool to slice around the perimeter multiple times to loosen everything, followed by some gentle and slow prying with the blue plastic prying tools and ending with strategic aggressive prying with the metal scalpel tool. It took a while and a lot of patience but I was eventually inside.
Once inside, I saw that the main culprit that caused so much resistance were two plastic stand-offs that were kind of connected to two screws in the body of the burger. I say 'kind of' because they weren't necessarily fused, but they were definitely snapped together with the intent to never separate. A small bit of plastic damage did occur upon opening to the stand offs, but nothing devastating or even really noticeable.
The circuit board for the phone was really fun to look at. I was able to identify the two ICs that make up the board. The first being a HM9102D, which is an 18 pin chip that has the responsibility of being a "Switchable Dialer". When I was first looking at this chip, I assumed it was some sort of multiplexer because of the size and also the fact that the leads from the numpad were connected to it, but this chip actually decodes the numbers to be tones to dial a phone number along with some other functions. If you want more information on this, you can find a datasheet here.
The second IC is a bit smaller in a DIP-8 package and as a result I first thought it was an op amp. It's actually a K2411 Telephone Tone Ringer. It does what you'd except: outputs a tone that rings the phone. For more information, I also found a datasheet for this chip here.
RepairBut after stalling with some circuit board eye candy, it was time to get out the soldering iron and try and repair this phone. During my ogling of the board, three wires fell off their solder points. I say fell because after looking back at the footage the wires basically tore off from their solder points with little to no exertion. The culprits were the two red and green wires in the actual phone line (kind of important, more info here) and one of the leads from the piezo speaker at the bottom of the phone which allows the phone to ring. So now on top of the original problem I had some board rework to do.
Reconnecting those runaway wires wasn't too bad. I just stripped back some of the insulation, reflowed the necessary solder points and soldered the wires back. I was glad that I had taken the time to photograph and film the board so closely, otherwise it would have been more of a guessing game as to where I needed to reconnect the runaway wires. In hindsight, I wish I had replaced all of the wires with more heavy duty wire that I had on hand but I was a bit too preoccupied with making sure I could get the phone back together. If this phone gives me issues in the future though, I'll definitely do that.
Speaker CableFinally, I got to the original problem at hand: the broken speaker cable. At first, I thought I had enough clearance from the top bun portion to access that piece of the wire but I quickly realized I needed some more leeway if I was going to strip back the wire casing. I had also realized that it was a dual core wire carrying a signal and ground, which makes sense but complicated things a bit.
I tried without success to open up the top portion of the phone but it was just impossible without doing serious damage. I could see thru the gap that a similar plastic standoff assembly was inside that was also present in the body of the phone and I just couldn't get the right combination of force and angle to safely crack it open without, um, cracking it. What I ended up doing was using one of the plastic pryers to wedge open the top bun just enough so that I could get my ESD tweezers inside to pull the speaker cable towards the front of the bun, allowing for enough slack to properly strip back the wire and solder the appropriate ends. Once I did this I was in business. Instead of soldering the original wire pieces back together, I used two pieces of jumper wire to lengthen the connection. I had heat shrink tubing ready to go but unfortunately I'm not sure where my brain went while I was putting it onto the wire because I cut two small pieces to go over the solder joints while neglecting to realize that a longer piece that could cover the entire jumper wire extension would have been a much more effective choice for both connection integrity and aesthetics.
Put it Back TogetherWith the soldering done it was time to put everything back together. This was basically without incident except for the neglect on my part to realize that obviously the wire would not fit back thru the hole at the hinge in the top bun portion. I slowly wedged open the top bun to pull the wire as close to the hinge as possible until I finally reached a point where wedging was not an option. I think this is actually a good thing though since the wire is now running out the side and will not be a victim of the hinge chomping away at the delicate connection every time the phone is opened and shut.
I did a quick test with the phone by plugging it into an active landline and success! I could hear thru the phone again! All other functions worked as well so my other repairs were also successful and nothing else was a victim of my teardown. Since then I have also had success with it in my apartment as a buzzer. I can finally know with certainty who is entering my building, which you'd never know was a luxury until you no longer have it as an option.
I hope people that read this will be empowered to repair their own items, even if they're going in blind like I basically was here. Of course, safety is always paramount, but with a little common sense and research, most things can be safely repaired. If nothing else though, I think we all learned why Juno had to shake her hamburger phone so much to be able to hear properly. After seeing the integrity of the wires inside, it all makes perfect sense.
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