Help identifying Motorola diode.

Hi all, I'm trying to identify a Motorola surface mount diode.

The code on the didoe is 607 with a datecode of 9318. It's a Motorola from the logo. I've not had success with google trying to find it, would anyone have any ides? I think it's azener, or perhaps a schottky.

Thanks Greg (sorry if this posts a second time, tpg doesn't seem to post out)

Reply to
gcd
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I can find a Motorola reference referring to their 1N607 and 1N607a diodes, which the reference states can be replaced with a 1N4001 - far from a Zener! Whether the "607" on your device refers to 1N607 or something entirely different though, is anyone's guess.

The reference sheet's here; click the thumbnail to download the PDF -

formatting link

You might want to contact WES in Ashfield (Sydney) and ask for their thoughts; though I haven't dealt with them in several years, I remember their staff being very knowledgable.

--
Bob Milutinovic 
Cognicom
Reply to
Bob Milutinovic

"gcd"

** Why not test it - if it still functioning.

... Phil

Reply to
Phil Allison

Hi, I'm reasonably sure it's damaged.

I didn't reverse engineer enough of the circuit and found this diode directly across a filter cap after a 2 diode rectifier in a smps after it heated enough to melt the solder on the board. (wound the external supply up to 15V with 100-150mA current limit set).

So the diode now measures around 0.7V forward and breaks down at around

17-18v.

In the circuit it's directly across the filter cap with no current limit resistor so I've either damaged a 15v zener or I've damaged a 15v schottky that was there for some unknon reason.

I've checked all the smd code websites and pdf that I can find but no reference to a motorola diode with code 607.

I'd suspect a 15V zener but I'm loathed to put one in there with no resistor. The smps circuit maintains it's fault without the diode, so I can still do some fault finding.

Greg

Reply to
gcd

Hi, no it's not a 1N400x type didoe, it wouldn't have broken down at around 15v. See my reply to Phil, I expect it's a 15v Zener. Also, looks like the 1N607 is a DO-4 case style, not an SMA or SMC surface mount type case.

Thanks Greg

Reply to
gcd

. . .

Transient suppressor maybe?

Did you try searching for Onsemi instead of Motorola?

Andy Wood snipped-for-privacy@trap.ozemail.com.au

Reply to
Andy Wood

"gcd"

** SMPS often have sacrificial zeners across DC outputs.

When the PSU goes haywire and the DC voltage rises out of control, it fails short and prevents harm to the attached load.

A crude crow-bar circuit, in fact.

... Phil

Reply to
Phil Allison

zener it is then, wasn't aware that such techniques would be used, particularily as this smps is form a rather expensive hf receiver.

thanks Greg

Reply to
gcd

Sounds like maybe a zener, while regular diodes can drop as much as 1.1V at max rated current, 0.7V is regarded as "nominal". In actual fact; a DMM diode check is likely to show nearer 0.65V (even lower for fast diodes) - the diode check will actually show 0.7V on a zener.

Shottky-barrier diodes vary considerably depending on current rating, I've measured as low as 0.1V for big stud mounted rectifiers, and (I think) about

0.4V for the likes of a 1N5817 etc.

The low reverse breakdown adds credibility to the idea of it being a zener.

Reply to
Ian Field

Phil is probably right with "crude crow-bar" - the not so cheap & nasty version uses a zener (taking Vgate into account) to latch a SCR across the rail, a fuse is pretty much essential.

Reply to
Ian Field

Hi, the 15V breakdown also made me consider the schottky, that's a typical schottky breakdown voltage. But a zener sounds more logical than a schottky. However such a brute force approach is likley to cause collateral daamge within the smps than something more elegant.

Cheers Greg

Reply to
gcd

"gcd"

** Like hell it is.

** Wired in parallel with an electro - of course it's a zener.

... Phil

Reply to
Phil Allison

Hopefully your SMPS has an overcurrent trip.

BTW: you're unlikey to find many SB diodes less than 20V, except in VHF/UHF small signal applications.

They do however get used as sacrificial crowbars - I've found them occasionally protecting the G-S of the SMPS MOSFET in PC monitors - more often than not regulation failure caused core saturation and blew the internal structure of the MOSFET and/or the source current sense resistor, if the clamp diode protected anything at all - it was usually the SMPSU chip.

Reply to
Ian Field

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