Taking apart a Nokia 105

· by joe · Read in about 5 min · (933 Words)

New year reflection led me to the conclusion that perhaps having email, twitter, facebook and the Internet at large following me round in my pocket all the time wasn’t a great idea, so I thought I’d get a phone that wasn’t afraid to revisit issues of self-identity. The Nokia 105 makes phone calls, sends texts, has an FM radio and not much else. I’m very happy with it.

One problem I noted in reviews was that the ear-speaker was too quiet. I found this to be correct. In their pursuit of the bottom line (this phone really is very cheap indeed) they combined the loudspeaker with the ear-speaker. The result is that it’s easier to hold a conversation by holding the phone back-to-front than with the screen to your ear. I felt felt a bit strange having conversations knowing that my phone was broadcasting more sound away from my ear than into it. This is a failing, I think.

I opened my phone in an attempt to solve this problem and to see how it was put together.

This is the front of a Nokia 105. The screen is nice and bright. The keys are tactile, but the single piece of rubber means it’s difficult to type by touch. Light in the hand, good mouth-feel.

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This is the back with the battery removed. There are two obvious Torx screws which need removing. There are clips inside.

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I stuck a knife in the gap and … just kind of got it apart. It helps that the phone is so cheap. I’d love to say that I carefully prized back the clips but it was more of a holistic process than that. Here are the tabs (from memory, there may be more).

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The back is another piece of injection moulded black plastic in a special shape determined by one or more designers and engineers employed by Nokia or its agents or subcontractors. Nothing much to note except for the slightly alarming crocodilian spring-contacts for the headphone jack.

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Oh, except, you know, the large speaker. Yes, you are looking from the front of the phone. Yes you are looking at the back of the speaker. Yes it’s facing away from your ear. Yes that makes it hard to hear your conversation partner.

Here is the back front of the speaker

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One surprise I found when using the phone was that, upon plugging in standard issue headphone+microphone (four conductors) into the headphone socket I was greeted with ‘accessory not supported’. It fits into the socket but it isn’t a supported accessory. Here’s proof that only a standard three-conductor length plug fits.

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It’s a cheap phone, don’t push your luck. Still, slightly disappointing and wouldn’t have cost them anything to support my accessory.

And so onto fixing (or ameliorating) the speaker problem.

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The speaker sits diaphragm-down in that circular bezel retained by those clips. Beneath it sits a gauze, through which you can see the table behind. This is how sound escapes backward. The hole at the top is where sound comes out at the front. Sound heads through the channel (right-hand blue arrow) into my ear (or yours if you can imagine the arrows pointing to the inside of your phone). It also heads through the entry (left-hand arrow), maybe into a sealed enclosure, maybe into the earpiece. I didn’t check.

I imagine there’s some clever acoustics going on. I didn’t remove the foam gasket that seals the sound-chamber. But I do know that the letting the sound from the front and the back of a speaker diaphragm meet without taking extra measures is a bad idea.

There’s no point trying to flip the speaker to face the other direction. Instead I decided to fill the back-grilles with sugru. I put the putty in the holes and scraped off the excess.

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And the back:

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I’m aware that this will have a detrimental effect on the sound quality, turning the speaker from an open-back to a closed-back design. However, I think it’s an improvement in overall usability and I stand by the decision.

I then did something stupid which I don’t stand by, which is try to enlarge the speaker grille size on the front.

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Like I said, it’s a cheap phone. I don’t mind a cracked screen that much.

Finally, here’s some exciting pictures. First, the reverse of the PCB. Notice the microphone at the bottom. All the chips are inside that RF enclosure behind the sticker. That white thing right at the top is an LED for the ‘torch’. Bottom left looks like an antenna connector.

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And immediately beneath that. Is that an antenna-on-a-PCB? With overlapping traces and vias?

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Draw your own conclusions. There’s something right at the bottom of the PCB that looks more like an antenna. In which case what’s the thing on the bottom-left?

Finally, the keypad in a blaze of glory, loosed, temporarily, from its rubber prison.

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My conclusion? It’s a good phone, you should get one. I got about 4 days out of the battery with about an hour’s talking each day. It feels light in the hand. You should make the speaker modification, although you should probably do it with blu-tak and you should probably do it without taking the phone apart.

My conclusion about having a phone without a data connection? Do it. It’ll put years on your life.

One outstanding mystery. There is a vibrator in the phone. I couldn’t find it anywhere. If you take your Nokia 105 apart please have a look and let me know, I’m baffled. Unless it’s hiding in the keypad somewhere.

 

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