Diode identification?

It's shorted, burned on the side against the board, the side of the diode that has part of the p/n printed (of course)...

Best I can make out is (reading around the diode: ITT 4? 47

Physically it resembles a typical 1A black epoxy rectifier.

Would this be 1n4147? The "47" is clearly visible, and I think I can make out a "4" in the first part of the poorly-legible digits. No telling how many digits between the two "4"s.

Any possibilities other than 4147?

Thanks,

--
John English
Reply to
John E.
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Not wishing to trach granny, but this would be my approach:

Reverse engineer parts of the associated circuitry until I am reasonably confident of what sort of application it is being used for, eg lf rectifier, hs switch, flywheel, etc. Or more importantly, if it is a zener.. It is normally not to difficult to work out what the diode is doing and what sort of currents, voltages and frequencies are happening to it.

At that point, wire in an external diode with a much, much higher spec than the original - and measure the actual running parameters. I keep a few huge and very expensive semiconductors just for this.

Then match a diode to that requirement, by measuring what is actually happening - with any luck the spec will match to something with a lot of

4s and the odd 7 in its product name.

Assumptions about what things may be tend to bite..

--
Sue
Reply to
Palindrome

Ah, another ITT diode on the board starts with "ZY" (where "Z" could be mistaken for a "4" on the charred carcass). So I looked up ZY47 and get a

4.7v power zener diode, 2W.

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Also, according to a National data sheet I found, a 1N4147 (a.k.a. 1N914A) is glass, and way too lightweight physically compared to my charred sample. Wrong turn, I think.

So it looks like ZY47?

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John English
Reply to
John E.

John You can't just guess at this. As sue suggested, you need to look at the circuitry and figure out what that diode function is. What is the circuit for? What components are near the diode? Can you trace the diode connections to the next devices? What are they? Once that is determined, there are likely substitute devices that will work just fine, even if you can't identify the original. I do this all the time as I restore a lot of old test equipment. It can be a challenge when you don't have the schematic, but generally you can get there with enough patience and logical thinking.

Ben Miller

--
Benjamin D. Miller, PE
B. MILLER ENGINEERING
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Reply to
Ben Miller

Ben Miller sez:

OK, here goes: German-made paper-handling machine, c. 1989. Circuit activates solenoid, taking several inputs from other sensors, signals, etc.

Anode of unknown diode is to ground, cathode to drain of BUZ72 MOSFET. 1uF cap also from drain to ground. Drain connects to solenoid. Drive voltage is

42vdc.

Thanks,

--
John English
Reply to
John E.

Not then, I would suggest, a 4.7v zener ... Sounds like it's just a flywheeling diode and a 1N4007 would do the job just fine. Does the FET source go to ground ? Many power MOSFETS have a diode internally in that orientation across from the source to the drain. It gets there as an integral side effect of the manufacturing process.

Arfa

Reply to
Arfa Daily

Newer designs seem to use a fast-recovery diode (e.g. FRED or HEXFRED or HiperFRED) for MOSFET flyback protection. 1N4007s aren't particularly fast, and reverse-conduction losses can be significant if the switching frequency is high (in e.g. an SMPS). That's probably not all that much of an issue in a solenoid driver, though.

--
Dave Platt                                    AE6EO
Friends of Jade Warrior home page:  http://www.radagast.org/jade-warrior
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Dave Platt

Palindrome wrote in news:LQYFh.91285$ snipped-for-privacy@fe07.news.easynews.com:

I hope it doesn't come to that, if she has any breathing difficulties at all, I imaging it's just due to the rarified air of this place.

Reply to
Lostgallifreyan

The diode is a snubber to bypass the inductive kick from the solenoid when it deenergizes. A 1N4007 will work fine.

Ben Miller

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Benjamin D. Miller, PE
B. MILLER ENGINEERING
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Reply to
Ben Miller

That's not what either a 1N4147 or 1N4447 looks like.

Graham

Reply to
Eeyore

BZY47-C47?

2 watt zener 47V ? The number after the C is the voltage. 4.7 volts would be BZY47-C4V7 btw.

Graham

Reply to
Eeyore

On Fri, 02 Mar 2007 16:49:16 GMT, John E. put finger to keyboard and composed:

Go here ...

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$$Search?OpenForm

... and type the following into the search box:

1n4*47

- Franc Zabkar

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Please remove one 'i' from my address when replying by email.
Reply to
Franc Zabkar

That was my thought, and the reason that I suggested a KISS approach with a

1N4007

Arfa

Reply to
Arfa Daily

Arfa Daily sez:

The source connects to a flame-resistant (blue), less-than 1-ohm, 1/4w(?) resistor (red-violet-gold-gold) that measures about 0.5 ohm. (It should measure 0.27, yes? Maybe candidate for replacement? But maybe it's my Fluke

77's accuracy at that low setting. Resistor doesn't look abused...) The other end of the resistor does connect to ground.

Yes, I've read about the need to short out back-EMF when dealing with relay coils, solenoids, etc.

So, 1N4007 it is.

An after thought... since the diode was cooked (it actually charred the PCB beneath it) but the resistor and the FET are OK, maybe the diode needs to be boosted to a higher A rating? Thoughts?

Thanks to all,

--
John English
Reply to
John E.

Black ? What size ? I guess 1n4007

1KV , ?1amp , 40 amp surge

____________________________________

Reply to
Werty

It seems my post aboutt his didn't reach the group.

It's most likely a BZY47-C47 2 watt zener 47V

Graham

Reply to
Eeyore

You would be wrong.

Reply to
Eeyore

Late at night, by candle light, Eeyore penned this immortal opus:

Spot-on I think. It'll normally have 42 V across it, not enough to conduct. When de-energizing there'll be a spike wich it clamps at 47 V. Dunno why the 1 uF cap.

- YD.

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Reply to
YD

German overkill engineering !

Graham

Reply to
Eeyore

So, if all the conduction it should get is from the odd spike, how come it got the San Quentin hairdo? It takes rather more than static to fry chips.

My thoughts would be that the supply rails are screwed. If the unit has a positive and negative rail, it may be that the ground return to the psu has problems and thus more than the 42v is appearing across the zener, as the ground point has shifted towards the negative rail.

--
Sue
Reply to
Palindrome

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