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 Forum index » DIY Hardware and Software
Diode ID question
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numbernone



Joined: Aug 16, 2006
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Location: new york city

PostPosted: Mon Aug 21, 2006 11:31 am    Post subject: Diode ID question Reply with quote  Mark this post and the followings unread

My first cloning project is quickly coming to fruition, with one little boondoggle: identifying three tiny diodes!! Everthing I can comb from the net regarding testing and ID only goes so far as verifying that the part is good or bad. Even then it requires removing it from the PCB, which I want to avoid at all costs. It is a very old and small board densly packed with parts and I cant risk botching it at all ( I would dehydrate from crying). I have been able to ID all of the other parts by macro photos, but these damn diodes dont show any outward traits of ID.

Does anyone have any genius ideas regarding how to figure out the values of these buggers? Elsewise I will likely fill out the proto board and test a zillion types until striking gold. Im sure there are way better routes to take but I am merely a newbie tinkerer employing his own "scientific" methods... Smile Any help at all is straight from heaven.

Thanks.
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zipzap



Joined: Nov 22, 2005
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PostPosted: Mon Aug 21, 2006 11:58 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi
Do i understand that you want the exact diode because you want to clone the unit as good as possible?
What do they do (in the circuit)? Most likely you wouldn´t hear the difference to another type if it functions in some controll aspect. If it really does sound - well you´ve got all the rest right - find an old (germanium?) that sounds the same. Propably won´t take that long.
I´m no expert, but i have desoldered a lot of old diodes. No labeling, no ID. At least i can´t imagine. With some good lab you could maybe find out how fast/slow, (non)linear it is...

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zipzap



Joined: Nov 22, 2005
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PostPosted: Mon Aug 21, 2006 11:59 am    Post subject: Reply with quote  Mark this post and the followings unread

What is it, anyhow? Just curious.
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numbernone



Joined: Aug 16, 2006
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PostPosted: Mon Aug 21, 2006 12:19 pm    Post subject: Diode ID question Reply with quote  Mark this post and the followings unread

Its a KEIO sythesizer traveller pedal. Took the best part of 10 years to land it, and I am dead afraid of screwing with it too much, beyond all the prodding and probing so far. I have been able to locate pretty much every component to match, but the diode part has me temporarily stumped. I havent really laid out the schematic yet ( I only just began to run with this idea but I tend to get obsessive and want it sussed out NOW!!) so im not sure what their exact functions are as of yet.
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toppobrillo



Joined: Dec 10, 2005
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PostPosted: Mon Aug 21, 2006 9:44 pm    Post subject: Reply with quote  Mark this post and the followings unread

yes firstly it should be important to know what they do in the circuit, i dont know what the traveler is, is it a guitar effect or something? there are a few different types of diodes, but in your low-voltage/low-amperage type of circuit, it's prolly not too critical stuff at all, unless, of course, they are zeners or schottkys or something!

desoldering isnt too hard if you must, use 'desoldering braid' and dont apply heat too long at a time so you dont lift the trace. check for voltage drop, .6-.7 is silicon, .3 or so is Ge. oh, all the Ge diodes i have seen are bigger than the small-signal silicon type.

take a picture of the board close-up if you can

good luck

josh
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State Machine
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Joined: Apr 17, 2006
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PostPosted: Tue Aug 22, 2006 6:39 am    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
desoldering isnt too hard if you must, use 'desoldering braid' and dont apply heat too long at a time so you dont lift the trace. check for voltage drop, .6-.7 is silicon, .3 or so is Ge. oh, all the Ge diodes i have seen are bigger than the small-signal silicon type.


You may also want to see if it is a Zener diode by hooking it up in series with a 1K resistor, connect a variable power supply to the cathode end and a voltmeter across the resistor. When the voltage starts to rise, this will the Zener voltage of the diode. If you get up to 15 or 20 volts and still no voltage appears to rise across the resistor, then it is a conventional diode.


Power Supply ---------===-----------<><><-----------GRD.
...............................DIODE............... 1K
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