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Dissasebled DVD HELP Needed

norbyx

norbyx

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Well I had to throw away my car dvd since it wasn't working anymore. Anyhow I dissasemble it compleately and here is what I got:
Obviously a laser, a lens, a couple of mirrors (very small) and something I can't really tell what it is. I don't know if it's the laser pickup module or how it's called. Probably someone can tell me exactly what I am looking at, and what can it be used for. It's obviously that grey thing that looks like a laser diode but 2 times bigger...
BTW does anyone know what 28 TE means on the diode?




Ok so I took the diode off the board. Now I was looking to understand the pinout of this diode but it seems I can't find the information needed (yes I have searched already).
The diode has a big R on the back and it says 28 TEC on the case... any idea what diode it might be? It came from a cheap a$$ DVD player for a car.

 
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Sigurthr

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Re: Dissasebled DVD this is what I got

The larger encapsulated unit is probably the photodiode used to read the reflected laser beam from the disc.
 
norbyx

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Re: Dissasebled DVD this is what I got

That is what I thought. Good for me I actually needed one.
 
Cyparagon

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Re: Dissasebled DVD this is what I got

I'm pretty sure the optical pickup is more than a single photodiode. That is to say I've never seen one with only two pins. You sure it isn't the IR diode?
 
Sigurthr

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Re: Dissasebled DVD this is what I got

Cyparagon might be right. I don't actually know if they use photodiodes or phototransistors for DVD readers, and it depends greatly on the unit whether it used a single combo diode (658/780) or two separate diodes. I remember taking apart an old DVD reader that used a single combo diode for simpler sled construction.

You might want to add additional pictures. Also, simple wide spectrum photodiodes are available from most component sources (including radioshack) rather inexpensively.
 
norbyx

norbyx

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Re: Dissasebled DVD this is what I got

Here are a few more pics:
null_zps1a0ce1e3.jpg

null_zpsbaf0a719.jpg

null_zpsea0e6f15.jpg

null_zps8df8cfeb.jpg
 
norbyx

norbyx

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Re: Dissasebled DVD this is what I got

Well whatever it was it is no more... I took the back part off to see what came out and it was a strange looking thing that in my opinion is nothing near a laser.



So any clue on what the 28 TE stands for on the laser diode?
 
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norbyx

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Sorry this post was wrote by my 4 year old daughter... it wasn't ment as a double post. I just edited it..
 
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norbyx

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Ok new update (hopefully someone will read this). From another thread I read that a way to determine the pinout of a diode is with the diode test feature of the multimeter. Well I did it and off all the possible combinations I just one with voltage going through. Is this a correct way to find the pinout?
 
Sigurthr

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I've never been fond of the diode check method as many LDs have a built in photodiode which will invalidate at-a-glance readings with a DMM.

The way I always used was to make a CC CV 3.3V psu and manually check the biasing of the diode. If you set the current low enough, say 5mA, it is generally safe for any diodes you might encounter. I don't know of any LDs which have a reverse breakdown voltage of <4V, so it is generally safe in that regard as well.
 
norbyx

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well I can do that with my ps, but the question is, if I inverse polarize wont that damage the diode?
 
Sigurthr

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Not if you don't exceed the reverse breakdown voltage. Diodes are designed to allow current flow in only one direction, that is what they do. In a way the LED (and thusly the LD by extension) was a happy accident when they discovered that using special construction and materials diodes would produce photons when forward biased. The diode will conduct when the forward voltage is satisfied, so you can use any voltage greater than the Vf but lower than the Vbr.

Photodiodes are typically reverse biased and then conduct only when exposed to light. LEDs and LDs will do this too to a certain extent, but the sensitivity is greatly reduced.
 
Pi R Squared

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norbyx

norbyx

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It might be correct. I found the pinout, and the laser turned on briefly but it looked red and the pinout is the one of a red diode. Now I just need to get a module to test it better.
 
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