Puzzling diode

One picture is worth a thousand words.

Maybe ...

The "brim" is the cathode.

At a guess, they sound like a voltage reference part.

I'd probe it at low current for zenering behavior. Skinny top-hat DO6 (vs DO1, DO2, DO3, DO210AA) axial parts weren't suitable for HV service.

DO13 lost the top-hat while maintaining hermeticity.

That could also (almost) be a cyrillic marking, given the limited characters used.

RL

The way the supply chain shortages are going, dumpster diving might soon become a major source for components.

That's an old, late 1950's to early 1960's style package. They were called "top hat" diodes. Something like these:

I didn't have any luck finding who in-co might be. I found this:

but that's obviously not a diode manufacturer.

Judging by the lead diameter in the photo, methink the IC1790 is some kind of power diode, zener, or whatever.

Got a curve tracer? I can tell quite a bit about the diode from a curve tracer display:

or just build your own curve tracer:

Good luck.

Long shot ...

This is something in a similar type of package

It's called a transient voltage suppressor (TVS) - a kind of Zener.

Does that the diode logo have a straight thin line across it, or is the line bent with angular tips?

There are also some diode manufacturers that use the diode symbol in their logo.

A picture of that symbol would be great as well.

snipped-for-privacy@gmail.com wrote: ========================

** I guess you have verified it is a Si diode with your DMM? With bench PSUs it is easy to get other specs.

Maybe connect one across a standard ( not alkaline) AA cell a see what happens.

...... Phil

On 4/7/2022 4:46 PM, Adrian Caspersz wrote: > Does that the diode logo have a straight thin line across it, or is the > line bent with angular tips? ... >

No, the symbol is just plain diode (triangle & strait bar)

On 4/7/2022 4:15 PM, Jeff Liebermann wrote: ... > I didn't have any luck finding who in-co might be. I found this: > ...

It's actually IN-COM - the "M" wraps around. But IN-COM can't be found either.

You say it could be late 50's - I think in the 50's there were a lot of transistor start-ups looking to get on the band wagon. If so, IN-COM could have been one of them that just faded away.

When I found them, there must have been a couple thousand of them. A wild ass guess would be that a town resident was involved with IN-COM & took some home. That resident now down-sizing. Or similarly, a resident involved with a company that used this diode in a product.

Some crude bench supply tests: handles 3A forward (1V drop), getting warm. The heat from 5A (8W) discolors it, but it doesn't open (10 minutes). It breaks down with reverse voltage of 80V (peak, 60v RMS full wave).

snipped-for-privacy@gmail.com wrote: ========================

** Hmmm....

You have a pretty ordinary 3A Si diode.

The modern 1N5401 has much lower forward voltage drops.

.....Phil

1N1790 is a 62V 10% 1W zener.

RL

legg wrote: ===========

** Looks a hell of a lot like it. Made by Motorola and IR likely in the 60s or early 70s.

.... Phil

1S1790 is a 150V zener in that case size.

S is C in cyrillic.

RL

Perhaps an abbreviated >...

Oops. I took the name from your photo.

That's possible. However, the late 1950's guess is based on the prevalence of similar looking "top hat" packages. I vaguely recall that this package slowly disappeared in the mid 1960's.

That's exactly what happened to me when I was a senior in high school in 1965. I got a tour of PSI (Pacific Semiconductors). They were in the process of being acquired by TRW:

and were disposing of most everything with PSI printed on it. I went home with a large cardboard box full of floor sweepings. I probably could have gotten more if I transportation. Most ended up being redistributed to the schools electronics students. I went home with two shoe boxes stuffed with mostly diodes, some of which I still have today.

If the reverse breakdown voltage happens abruptly, that's zener action. 79V zener perhaps? However, if the reverse breakdown corner is gradual and rounded, it's an ordinary power diode. Throw together an I-V curve tracer and see what it looks like on an oscilloscope:

Here's another possible diode logo:

On 4/7/2022 9:16 PM, Bob Engelhardt wrote: ...

I was thinking these were plain diodes, since that is the symbol on them, so my test did not control the reverse current and let it vaporize.

I did another, with "pure" DC (instead of full wave) & limited the current. Also measured the current as it approached breakdown. It started at 46V (1ma), growing to 100ma at 62v, just before it broke down at 64v.

Then it went crazy: the voltage across it dropped to 7V (650ma) & 6V at

800ma. Is that the way a plain diode breaks down?

Since I limited the current, it did not vaporize and the test could be repeated.

On 4/8/2022 5:11 PM, Bob Engelhardt wrote: ...

Oh, wait ... once it broke down, the current through the limiting resistor (100R) dropped most of the voltage there.

On 4/8/2022 2:50 AM, Jeff Liebermann wrote: ...

Throw together

I had Googled DIY curve tracer & got really elaborate circuits, so I didn't pursue it. Is the one you linked to really all you need? (AC & 2 resistors)?

Doesn't that have the same problem that I had: once the diode breaks down & conducts, voltage is dropped across the resistors and the voltage across the diode drops, a lot?

==========================

** A 1W zener will not like 6.4 watts.

** That is failure, not breakdown. The Si chip has melted.

...... Phil