No Markings - Identify Part

[AtomSoft]

Anyone can identify this Diode? It has no numbers on it at all.

if this is in wrong section sorry please move it

 

[colin55]

What do you want to use it for?

It all depends on where you want to use it, so that we can advise as to how many determinations need to be made.

 

[AtomSoft]

Im not sure. I was trying to catalog all my parts and came across this. I think its a Zenor but not sure... heh the thing is i have about 80 of these if not 100. So would be nice to be able to label this part.

 

[cobra1]

Thats going to be difficult to catalogue, i use diodes in that package, they look identiacal. The ones i use are general purpose signal diodes.

 

[AtomSoft]

I guess Ill have to label them for that.

 

[Sceadwian]

Those are glass passivated diodes if that helps at all, doesn't mean they're a Zener, many small signal diodes are glass passivated. Zeners are almost universally low voltage so hook it up to a 20-40 volts supply in reverse with a limit resistor to keep it from blowing up and measure the voltage drop, if there is one that will be the Zener voltage, if it smokes it's not avalanche rated =)

I'd lean towards cobra's suggestion that they're just common 1/4-1/8th watt small signal diodes, good for lots of things.

 

[AtomSoft]

Ok ... So i guess i can call them General Purpose. Ill test one tomorrow with a resistor heh.. im so tired today.

 

[unclejed613]

zeners are usually marked, even little surface mount ones. my guess is 1N4148, which is about the most common diode on the planet.

 

[colin55]

A 1N4148 is simply a 140v zener, so you can test it.

 

[AtomSoft]

Heh i feel like staying alive today. Ill assume they are 1n4148 and label / treat them as such. Too much work today to be testing this

 

[Sceadwian]

A 1N4148 is simply a 140v zener, so you can test it.

Really? So they're avalanche rated at breakdown voltage? PIV tests are far different than an avalanche rating.

 

[colin55]

I simply said you can test it for zener breakdown at between 90v and 140v.

I use this feature all the time to pass signals above 100v

Don't try to conjure up more than the OP requested. This is not a synchrotron symposium.

 

[Sceadwian]

I simply said you can test it for zener breakdown at between 90v and 140v.

You failed to mention that the current limit resistor is very different in both cases and the wrong one can let the smoke out.

 

[colin55]

You failed to mention that the current limit resistor is very different in both cases

In this case. No it's not.

You test the diode for zener beakdown at 3mA to 5mA.

 

[Sceadwian]

I stand corrected, your 3-5ma test sounds good for both cases, didn't think it through all the way before contradicting you, my apologies. Where did you come up with the 3-5ma value? Just curious as I've not really studied zener data sheets to any degree and I'm curious how a typical zener PDF states the current it's Zener voltage is specified at.

 

[colin55]

The zener current is specified at the wattage-rating of the zener diode. The minimum current is about 1mA for 300mW devices. 2-5mA for 400mW devices and about 10mA - 20mA for 1w devices.
For a 1N4148 the wattage is about 200mW - 300mW. Only allow 3mA for a short period of time when testing. When the diode (zener) is used in a circuit and it dissipates half or less current than its wattage-rating, you can increase the current 50% or so.
Its all a matter of feeling the diode and if you can't hold it, it's getting too hot. Keep things as cool as possible.

 

[Sceadwian]

The 1n148 is not a Zener.

 

[colin55]

I have absolutley no idea what a "1n148" is.

How do you think they test a diode to determine what its PIV is?

 

[Boncuk]

The packages are MELF or MINIMELF depending on length and width.

I'd consicer them to be 1N4148.

Boncuk

 

[KeepItSimpleStupid]

In any event having a hundred or so, loosing a few isn't a great loss. Reverse breakdown is non-destructive if you keep the current low enough.

What kind of values to you get with the diode test on your ohmmeter?

1n4148's are very common and come in a glass body. Usually Vf is a little high.

Send me one, and I'll measure the reverse current for you. The cost of first class postage.