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Author Topic: PN3500 by Motorola  (Read 1265 times)
W6EM
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Posts: 1667




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« on: November 15, 2017, 09:35:50 AM »

Have about 50 of these in the parts drawer.  Can't seem to find a datasheet.  I tend to think they might be the same as a 1N3500, but not sure.

Anyone have an idea what they are?
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W6EM
Member

Posts: 1667




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« Reply #1 on: November 15, 2017, 01:52:01 PM »

It's apparently not a 1N3500 as the Vz is much higher than the 6.1V listed for a 1N3500.  With my power supply, I can't raise it high enough to see the breakdown.

It's Vf is 0.77V, which is well above a normal Si PN junction.

I think they might be PIN diodes, as when Googling I get a hit on an HP cross reference.
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KD0REQ
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Posts: 2023




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« Reply #2 on: November 15, 2017, 03:19:02 PM »

is this a diode or a transistor?  the PN prefix on transistors applies to plastic-case transistors that originated as TO-5s.  lower cost, lower dissipation, typically think 300 mW instead of that the TO-5 version carried.
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W6EM
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Posts: 1667




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« Reply #3 on: November 16, 2017, 02:25:49 PM »

It's a diode.  Small, like the size of 1/2w zener diodes.  I think now that it is a PIN diode with its higher than normal forward voltage.

They're old, so wanted to know what they are as I found them in sorting my mixed zener parts drawer.

I know about the PN prefix in lieu of the 2N, but these appear to have a glass or ceramic enclosure, not plastic.  And, I did test them to make sure they weren't another version of 1N3500 zeners.

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W6EM
Member

Posts: 1667




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« Reply #4 on: November 16, 2017, 07:39:56 PM »

W9IQ identified them as likely MPN3500 PIN diodes.  Oddly, they only have "PN3500" on the case.

73.

Lee
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WD4HXG
Member

Posts: 298




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« Reply #5 on: November 18, 2017, 03:50:35 AM »

Motorola as well as many other vendors frequently do not
mark a part with a complete part number but rather their
proprietary part code. Many of the SOT-23 transistors are
marked with designators such as '1LT', '3A', 'J2' etc.  Even
the larger metal T-03 metal cased power transistors were
frequently marked with codes rather than actual part
numbers. It is a pain if you do not have the magic decoder
sheet supplied by the manufacturer. Even more frustrating
is when two parts are very close to each other but one is
labeled 4RT3 and the same package part from the same
manufacturer is also labeled X45Z since it was supplied to
another customer after being screened by the manufacturer
for a customer's unique requirement.

If you have ever wondered why some ops hoard manuafcturer
data sheets now you know.

Chuck
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WB6BYU
Member

Posts: 17192




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« Reply #6 on: November 18, 2017, 10:45:55 AM »

As parts get smaller, it gets harder and harder to fit the full part number on the case in legible type.
We had a specific protocol for choosing which portion of the part number to use, as often we also had
to include a date code and lot number as well.  As parts got smaller, often we could only fit 2 or 3
digits on the case:  that's why for SMD transistors and such, the manufacturer will specify a two
character identifier, as there isn't room for any more.  (And even at that, I carried a lighted magnifier
to read the markings.)

A typical glass diode may be just large enough for 6 digits, in 3 rows of 2 (such as "1N4148"), so
it isn't surprising of a 7-digit part number get shortened.


The 2N... and 1N... numbers are JEDEC standards.  If a 2N2222 is defined to be in a TO-18 metal
case, you can't just put the same chip in a plastic case and call it a 2N2222 because it wouldn't meet
the specs.  But "PN2222" isn't covered under the standard, so a manufacturer can use that for their
plastic part, or "MPS2222", or some other variant.  There is no guarantee that it will meet all the specs
of the original part (heat dissipation, for example, will be lower in a TO-92 package) but typically it
has the same chip inside as the metal can version would.

Then there are the manufacturer part numbers for parts that aren't on the JEDEC standard list.  Sometimes
these are set by the semiconductor manufacturer (the "MPSxxxx" series from Motorola, for example), and
sometimes by a large customer who has specific requirements and may procure parts from multiple vendors.
We see a lot of surplus Tektronix transistors marked, "151-xxxx", some of which cross to standard JEDEC
parts and some don't.  The first three digits indicate the type of part, so we "152-xxxx" for diodes, and others
for integrated circuits, resistors, capacitors, screws, etc.

As a manufacturer building custom parts for various customers, it doesn't make sense to get a JEDEC number
assigned to it (unless it goes into a military product, when it may be required).  In that case you'll probably
just see a manufacturer part number of some sort.
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W6EM
Member

Posts: 1667




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« Reply #7 on: November 24, 2017, 11:50:30 AM »

Many thanks to all for helping me identify them.  If, by chance, any of you would like a few, shoot me an SASE to my home and I'll send some.  For an old guy at my age, 24 of them won't be needed.....

73.

Lee
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