What is this?

M

munkle

[H]F Junkie
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Jan 16, 2005
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This thing is dead on my fan controller, all the others have voltage at both ends this one doesn't. I'm not sure exactly what it is?
 
When you say "dead", do you mean that when the fan controller is running, there's no voltage across it? Did you measure both ways?

I think you're reading the number upside down. A lot of diodes are 2N<something>. In this case, though, it looks like all the diodes are the same. There are two things you need to look for: Vf (forward voltage), and either continuous current rating or continuous power rating. Since this diode is likely the same as all the others, you can find Vf by measuring it for the other diodes. Black multimeter lead goes on the end with the silver stripe, red goes opposite. The current rating you'll only be able to get from a datasheet, which is why you need the number off the diode. Can you post more pics of the fan controller, along with the model? Do you have any specs for the fan controller?
 
Mohonri said:
When you say "dead", do you mean that when the fan controller is running, there's no voltage across it? Did you measure both ways?

I think you're reading the number upside down. A lot of diodes are 2N<something>. In this case, though, it looks like all the diodes are the same. There are two things you need to look for: Vf (forward voltage), and either continuous current rating or continuous power rating. Since this diode is likely the same as all the others, you can find Vf by measuring it for the other diodes. Black multimeter lead goes on the end with the silver stripe, red goes opposite. The current rating you'll only be able to get from a datasheet, which is why you need the number off the diode. Can you post more pics of the fan controller, along with the model? Do you have any specs for the fan controller?
Click to expand...

It's a 6 fan fan controller, one of the fan controllers doesn't work. All the diodes have voltage on both ends except the one with the arrow, it only has voltage on one of the ends. If I bridge both sides with a piece of metal the fan turns on, removing the metal the fan turns off on that channel.

This is the fan controller.

I didn't get any readings putting the black on the end with the silver strip, and the red on the opposite side. However if I ground the black and use the red on the side with the stripe I get 12.00v and on the opposite side I get 11.66v on the diodes that work.
 
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Hmmm. To be honest, I'm not sure what's going on, then. Is there any chance you can post pictures front/back of the whole circuit board?
 
Here's pics: The wire bridge is power, ground, and the 2 sensor wires for 2 of the fans.




 
You were right I was reading it upside down. I went down to radioshack and I found a matching diode what is written on it is actually IN4001. I was having a hard time trying to figure out what the upside down 4 was haha. :p
 
Ok, I think I understand how it's supposed to work, although that doesn't help me understand why it's not working. The big black plastic things on the board with the diodes are transistors (either PMOS or PNP), and the six knobs are potentiometers which control how much current goes to each fan. The six diodes are freewheel diodes--they're there to protect the transistors if/when the fan is spinning faster than the transistor expects it to.

I suspect that something caused the diode in question to fail, and because it could no longer protect its transistor, the transistor also failed.

Next step: measure continuity between the not-silver end of D4 and the pins on Q4 (assuming they are paired). If there's no continuity there, then poke around the other transistors until you get continuity. That'll be the transistor you need to replace. Note: The middle pin of the transistors doesn't count! It has to be one on either side. If you can read the part number off those transistors, it'll help greatly in finding a suitable replacement.
 
Looks to me like typical lm317 circuits. Any readable part number on rectangular parts? Run a diode test on the diode, should read something like 0.6v for forward voltage drop
 
I replaced both the diode and the transistor and it is working now. Thanks for the help! Hardest part was finding the transistor it was either buy a pack of 10 on ebay for $7 from china, or pay like $5 shipping on one for 50 cents from a electronics site.

I finally found a nice electronics parts store in my city and got one for $2. Since I bought this thing I think for $12 I didn't want to spend $5 or $7 to fix it.

If I remember correctly I may have 2 had two fans plugged into that header at one time so maybe I overloaded it?
 
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munkle said:
Do you know what the specific one I need is, everything I can make out on them is readable in the pictures 10 something
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its a 1N4001 diode... its a common high voltage rectifier diode...... this is a very common diode just search it and you should find all the info you need....
 
thaltek said:
its a 1N4001 diode... its a common high voltage rectifier diode...... this is a very common diode just search it and you should find all the info you need....
Click to expand...

umm... I did replace it, and the transistor too, right above your post.
 
munkle said:
I replaced both the diode and the transistor and it is working now. Thanks for the help! Hardest part was finding the transistor it was either buy a pack of 10 on ebay for $7 from china, or pay like $5 shipping on one for 50 cents from a electronics site.

I finally found a nice electronics parts store in my city and got one for $2. Since I bought this thing I think for $12 I didn't want to spend $5 or $7 to fix it.

If I remember correctly I may have 2 had two fans plugged into that header at one time so maybe I overloaded it?
Click to expand...
Glad to hear you got it working. It's possible that you overloaded the fan controller-it all depends on what kind of transistor it was that failed.
 
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