# Diode identification?

J

#### John E.

Jan 1, 1970
0
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,

P

#### Palindrome

Jan 1, 1970
0
John said:
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?
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..

G

#### Genome

Jan 1, 1970
0
John E. said:
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,

Unfortunately a 1N4147 is a small signal glass diode.......

I would take a guess that what you have got is a zener diode.

Try googling for a 1N4747.

If it's fucked then something else might have fucked it so check the rest of
the circuit. However it sounds like it might have been slowly fucked so you
might want to re-design the circuit.

DNA

J

#### John E.

Jan 1, 1970
0
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.

http://www.allcomponents.ru/diotec/zy47.htm

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?

B

#### Ben Miller

Jan 1, 1970
0
John E. said:
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.

http://www.allcomponents.ru/diotec/zy47.htm

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?
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

J

#### John E.

Jan 1, 1970
0
Ben Miller sez:
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. ...

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,

A

#### Arfa Daily

Jan 1, 1970
0
John E. said:
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,

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

D

#### Dave Platt

Jan 1, 1970
0
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.

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.

L

#### Lostgallifreyan

Jan 1, 1970
0
Not wishing to trach granny, but this would be my approach:

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.

B

#### Ben Miller

Jan 1, 1970
0
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.

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

Ben Miller

E

#### Eeyore

Jan 1, 1970
0
John E. said:
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.

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

Graham

E

#### Eeyore

Jan 1, 1970
0
John E. said:
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.

http://www.allcomponents.ru/diotec/zy47.htm

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?

BZY47-C47?

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

Graham

F

#### Franc Zabkar

Jan 1, 1970
0
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,

Go here ...

http://nte01.nteinc.com/nte/NTExRefSemiProd.nsf/Search?OpenForm

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

1n4*47

- Franc Zabkar

A

#### Arfa Daily

Jan 1, 1970
0
Dave Platt said:
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.

That was my thought, and the reason that I suggested a KISS approach with a
1N4007

Arfa

J

#### John E.

Jan 1, 1970
0
Arfa Daily sez:
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 ?

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.
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.

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,

W

#### Werty

Jan 1, 1970
0
Black ? What size ? I guess 1n4007

1KV , ?1amp , 40 amp surge

____________________________________

E

#### Eeyore

Jan 1, 1970
0
John E. said:
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?

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

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

Graham

E

#### Eeyore

Jan 1, 1970
0
Werty said:
Black ? What size ? I guess 1n4007

You would be wrong.

Y

#### YD

Jan 1, 1970
0
Late at night, by candle light, Eeyore
BZY47-C47?

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

Graham

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.

E

#### Eeyore

Jan 1, 1970
0
YD said:
Dunno why the 1 uF cap.

German overkill engineering !

Graham

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