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Protection diode melted and burnt

wolde cosgrove

Jul 6, 2015
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Hi Experts,
I have been encountering diode protection burn-out, thats the diode D1 OPN:1N4148W-E3-08 got burnt and failed. Further x-ray investigation shows internal wires melted and burnt die which leads to suggestion of electrical over-stress and large surge current. I attached the schematic enclosed.
Please advise what has went wrong and what additional circuit should be included to prevent such burnt-out from happening again. Thanks
Wolde
 

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Minder

Apr 24, 2015
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1N4148 is a little on the light side for that application, the minimum I would used is a 1N4000 series, I usually keep 1n4007 as it covers many eventualities.
Even a little high on the current rating would not hurt.
M.
 

morphingstar

Mar 1, 2012
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perhaps a 10 ohms resistor in series with the diode would limit the the capacitor inrush current initially. 10 is a guess, based on the 100 following.
 

davenn

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1N4148 is a little on the light side for that application, the minimum I would used is a 1N4000 series, I usually keep 1n4007 as it covers many eventualities.
Even a little high on the current rating would not hurt.
M.

agree totally with Minder
and " a little light" would be an understatement ;)
Their repetitive PEAK forward current is only 450mA
continuous forward current of only 200mA and dropping off from there as temperature rises


Dave
 

CDRIVE

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If we're taking a poll I'd leave C2 alone and replace D1 with a 1N400X series diode as others have suggested.

Chris
 

Kiwi

Jan 28, 2013
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C4 has a symbol that I am not familiar with. What type of capacitor does it indicate?

1N4007's are the only diode I keep, so fitting one would be my first move.
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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C4 is just an electrolytic. The diagram seems to use symbols in less than a perfectly consistent manner.
 

Kiwi

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Thanks Steve.
I also see that they use 100E instead of the usual 100R for R1.
 

davenn

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Thanks Steve.
I also see that they use 100E instead of the usual 100R for R1.

that one isn't so bad, I will regularly use it myself ...
Steve's comment on consistency is more important
ie. to use the same symbols / names across the whole diagram :)

Dave
 

CDRIVE

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that one isn't so bad, I will regularly use it myself ...
Steve's comment on consistency is more important
ie. to use the same symbols / names across the whole diagram :)

Dave

Dave, I'm unfamiliar with that. What does it represent?

Chris
 

CDRIVE

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Dave, I'm unfamiliar with that. What does it represent?

Chris
Dave, perhaps you missed this post. I'm struggling with the letter "E" relating to "R". I've always considered "E" as representing EMF.

Chris
 

Minder

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The E is sometimes used in place of R after a resistance value.
The SI or world International Standards indicates R as their standard.
Main thing is consistency and not mixing in a particular DWG or schematic.
M.
 

CDRIVE

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Thanks but still not clear how "E" equates to "R".

Chris
 

Arouse1973

Adam
Dec 18, 2013
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Thanks but still not clear how "E" equates to "R".

Chris

For some reason E was used because printers couldn't print the Greek letter "Ω" reliably. I have heard it was something to do with the Dutch. I don't remember any more. Don't know why they didn't use the letter R. Maybe it's just because they are E series?
Adam
 

davenn

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Dave, perhaps you missed this post. I'm struggling with the letter "E" relating to "R". I've always considered "E" as representing EMF.

Chris

sorry, Chris
I have been and still am really ill

I would only see it for resistors less than 1000 Ohms so eg 100E, 470E, 10E etc
if resistor was 1000 Ohms or greater is had a k 1k, 10k etc

I can find no references on the www other than the vague reference that Adam lists below ... it also reference to clarity of value when photocopying of circuits ( remember photocopying quality has come a long way in the last 30 something yrs
wasn't always as good as today)


For some reason E was used because printers couldn't print the Greek letter "Ω" reliably. I have heard it was something to do with the Dutch. I don't remember any more. Don't know why they didn't use the letter R. Maybe it's just because they are E series?
Adam


maybe ? :)


Dave
 

Minder

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The letters were introduced to replace the decimal point, 2M5 4K7 1R5 etc. due to the concern a decimal point may no be seen.
Max.
 

CDRIVE

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Guys, I want to thank you all for your input on this. I guess the guesses will have to suffice. Actually, since we're a scientific forum I think that I should restate that as an educated hypothesis. :)

Dave, I'm very sorry to hear that. I hate being bugged when I'm ill. Get well soon.

Chris
 

morphingstar

Mar 1, 2012
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E means 1, K means 1000, M means 1000000.
Capital letters for dimensions >1 ! Ignored in North America.
R means Resistance, C means Capacitance, L means Inductance.
m means milli 1/1000, u (micron) means 1/1000000, followed by n and p.
µ µ ascii: alt+230
 

CDRIVE

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I'm left speechless.

Chris
 
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