Are you pretty sure it's a Zener?

Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com

I'm going to guess it's a fast switching diode, like a 1N4149.  I used to pick those up from Radio Shack back in the day...

Dan - Owner
http://www.Hi-TecDesigns.com

Is it dead? Or can you take a few short measurements? That will usually tell what sort it is.

Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

It's dead so it has no conductivity. I didn't think it was a zener or a dual, but based on the numbers on the case that's all I could find.

I was thinking of just replacing it with a 1n4001 or 1n4148, 1n4149

It's in a power supply for a solid state audio amplifier so I guess it's pretty obvious what it is. I just wanted to figure this code out on the case to find out exactly what these are...

I find it odd to have no way to determine the diode # from the printing on the case.

I wouldn't say that it's obvious what it is. It's very dependent on how it's used in the power supply. You may have problems just replacing it with an ordinary diode. If it's a schottky in a switching supply, the performance of the supply would suffer with an ordinary diode. If it's a zener in a linear supply, replacing it with a non-zener would cause the supply to be unregulated and a higher output voltage would result.

Well, what can I do at this point? All I have to identify the diode is the numbers on the case and the physical dimensions of the case (4mm length and approximately 1.5mm in diameter)

I forgot I had a good board laying on the parts shelf. The diode measures 649 ohms and on the silkscreen it has a normal diode symbol not a zener symbol - I guess that's not saying much for this chinese outsourced board though.

The supply itself has two rectifier bridges with Ac in(2) and DC + out and DC - out (rs405L)

It has two large filter caps 4700 63V and two smaller caps next to those 4700 35 volt

If the good board works, measure the voltage of the diode while it's running and pay attention to which way the anode/cathode is pointing in respect to the higher voltage.  A higher voltage on the cathode side says it's most likely a zener.

Dan - Owner
http://www.Hi-TecDesigns.com

All the diodes on this board measure an equal voltage on each side.

This particular diode measures 2.3volts anode (+lead of dmm) to cathode (-lead of dmm) and of course with leads reversed measures -2.3volts

This diode connects between the emitter of a pnp (cathode) and the emitter of an npn transistor (anode)which then is connected to the base of another npn then goes through a few resistors eventually leading to a +dc source a ways down the line.

So would this be a switching diode? It seems that way to me.

Yep.
Just a blocking diode I think.
Try a 1N4148.

Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com

You got a circuit diagram? It would be reasonable to take a guess at likely function and performance requirement if we can see the surrounding circuit topology, although if it is a switcher then that might make the task somewhat trickier.
 

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  Sometimes I only open my mouth to swap feet...

I described the circuit above, I do not have a diagram, I could take some pictures though.

I just got my 4148's in - this is definately not a 4148. The case is larger than the 4148. I will try to get some good pictures and I will post a link soon if anyone is interested in solving this mystery.

Lay a 4148 next to the problem child for your picture.

Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com

http://www.bright.net/~jarc is the link to my pictures.


The two diodes grouped together are the 4148's and the smaller one with the thick glass case is the chinese bad diode.

Come to think about it they use g-luxon caps in this thing and the only decent brand of components I see are the ST microelectronics mosfets.

So maybe this is just some diode we have with a cheap junk chinese packaging on it... But regardless, it's great to receive these two diodes from mouser clearly labeled 4148 and then look at the case of these diodes and see "3 2c" maybe it's some code for the all the f grade diodes. (haha)

I forgot to add D102 is what we're looking at it's below the inductor(covered with heatshrink) on the top pcb picture. And on the bottom pcb picture it's near the bottom right (to the left of where the wire tie goes through the board)

Most of the bad diode looks to be glass compared to the 4148's, but it is indeed larger externally. But, the cores could probally be very close to the same size.

I'm just making a guess here, but these might be a higher power version of a 4148 style diode...?

Hey!

This isn't design work? Is it?

Or making valuable machinery work so as to save a company?

Is it about getting one piece of junk electronics up and performing again. Isn't it?

Is it really worth all effort?

It is against site policy. That's for sure.

Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

Nope.

Just a case variation since the whole thing is just in a "blob-oh-glass".

Since you don't have a schematic and those two look as close as many 4148's I've seen, stick it in and give it a try.  That's what you do here on a system that's um, this, ah...cheap.

If it was an expensive, important board you could spend hours actually drawing a schematic, then analyze it.  But this board?  Just try it.  The sooner the better.

Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com

Skogsgurra, I see nothing in this thread against site policy. A forum is a place to lend your knowledge to others faced with questions and discuss topics of interest. I had a question for personal use and design.

That's what I plan on doing, accuracy in this section shouldn't be of much importance as long as it serves its purpose. The other transistors near this one are different and look very much like the 4148, but these are slightly different. I am going to sort through a couple different styles and see if I come up with anything closer.

But in the meantime I am going to stick this 4148 in and thanks a lot for all your help itsmoked, macgyvers200.


P.S. It's not really that cheap, it's a nice Klipsch piece, but outsourcing these days...