What transistor is this?

[pucho812]

Looking at the photo looks like a national but looking up the numbers 417 shows up as bd417 pn3568 shows up as a transistor as well.

I am thinking pn3568, but a second opinion is good.

 

[pucho812]

sorry for  fuzzy photo....

top numbers are 417
then a PN
then 3568

 

[Brian Roth]

I definitely vote for pn3568.....I seem to recall "PN" numbers being same/similar as "2N".  471 would be a date code.

Bri

EDIT...my memory may be faulty, but I think a "PN" transistor may have a different pinout compared to a "2N".

 

[pucho812]

I definitely vote for pn3568.....I seem to recall "PN" numbers being same/similar as "2N".  471 would be a date code.

Bri

EDIT...my memory may be faulty, but I think a "PN" transistor may have a different pinout compared to a "2N".

yes, I was thinking pn3568  as well but got confused because of the 417 being first...

 

[Brian Roth]

https://www.mouser.com/ProductDetail/Central-Semiconductor/PN3568?qs=sGAEpiMZZMshyDBzk1%2FWiw99kSkYzPxmOHeqHB5vyQ0%3D

Seems that it may be  "end of life".

Bri

 

[pucho812]

https://www.mouser.com/ProductDetail/Central-Semiconductor/PN3568?qs=sGAEpiMZZMshyDBzk1%2FWiw99kSkYzPxmOHeqHB5vyQ0%3D

Seems that it may be  "end of life".

Bri

thanks Brian. I am sure it is, but there is always the occasional stash or NTE part...

 

[JohnRoberts]

I vote for national semi PN3568... there are data sheets around the internets...

JR

 

[RuudNL]

https://www.mouser.com/datasheet/2/149/PN3568-98271.pdf

 

[PRR]

> I seem to recall "PN" numbers being same/similar as "2N".  .... I think a "PN" transistor may have a different pinout compared to a "2N".

"PN" was a standard 2N metal-can part reissued in a plastic blob. The die inside should be the same. The pinout depends on the package; the two types wire the die to the legs different. But of course you always look-up the pinout for the part in hand, and verify it with ohmmeter, or now one of those $13 testers.

 

[CJ]

that's right the old motorola cans like the 2N3440

i was wondering why I-c was so hi

 

[clintrubber]

You was just curious to the transistor-type, or does it need replacing... or just for circuit-tracing?

 

[JohnRoberts]

that's right the old motorola cans like the 2N3440

i was wondering why I-c was so hi

The  3568 is what is called medium power. While rated for 1A of collector current the PN (plastic) package has a thermal resistance of 200'/W junction to ambient. A maximum 150' junction temps suggest that 1A collector current is not available with much (any?) voltage drop.

Further, the beta is only specified at 150mA. Another hint this is not a 1A pass element device. Perhaps used as a saturated switch for a major fraction of one amp (like relay/lamp driver).

I have seen medium power transistors used for low noise applications way back when (due to their low Rbb to handle peak current), even though they make no such low noise claims. As I recall such users had to sort through numbers of these to select out devices with significant process noise. 

JR

 

[pucho812]

You was just curious to the transistor-type, or does it need replacing... or just for circuit-tracing?

these transistors are all over relay cards in a desk owned by a studio in town.  The cards themselves are usually duel channel with 2 x relays and about 6 of these transistors on them, 3 per channel. While I do have a card that stopped working we were able to replace it with a spare card for now.  I don't have a schematic but will get to tracing one in the future...  At the immediate, I was just confirming what transistor this could be as both sets of numbers came up as a possible transistor and the desk is over 30 years of age and still holding up quite well.

 

[clintrubber]

these transistors are all over relay cards in a desk owned by a studio in town.

Ok, so they're not in any signal path providing eventual ehh, mojo... 

... at least I haven't seen any company promoting their gear by claiming sonic benefits of the utility components around the signal path (as long as they're transparant and not introducing any disturbances when doing their utility-thing)

 

[pucho812]

Ok, so they're not in any signal path providing eventual ehh, mojo... 

... at least I haven't seen any company promoting their gear by claiming sonic benefits of the utility components around the signal path (as long as they're transparant and not introducing any disturbances when doing their utility-thing)

No, no mojo in these just working the relay cards that switch things...

 

[JohnRoberts]

No, no mojo in these just working the relay cards that switch things...

sounds like a good application for a GP medium power transistor. 

As I mentioned relay/lamp drivers are typical applications.

JR

 

[clintrubber]

No, no mojo in these just working the relay cards that switch things...

I heard that for a very limited time, a special run could be ordered of these relay cards, using metal can types for these switching transistors... not hard to imagine that these are the ones you want  ;D 8)

 

[moamps]

.... the PN (plastic) package has a thermal resistance of 200'/W junction to ambient...

I've always wondered why  fully metal TO39 package (2N3440 mentioned for example) is rated to so poor/high RθJA (175°C/W to 220°C/W).

 

[pucho812]

good question...

 

[JohnRoberts]

I've always wondered why  fully metal TO39 package (2N3440 mentioned for example) is rated to so poor/high RθJA (175°C/W to 220°C/W).

Thermal resistance junction to ambient is basically about heat radiation from the surface of the device package, to the surrounding air. A similar size metal and plastic package will have similar surface area thus similar thermal resistance to ambient.

For today's TMI, back in the early days of plastic packaging, the devices were only rated up to 150'C junction temperature due to package instability, while metal packages were rated up to full 200' C (where the silicon die becomes unstable.) 

In the early days of plastic power transistors, eclipsing metal can power transistors in audio amps, there were designs that appeared to exceed the conservative 150'C peak junction temperature. Modern plastic packaging has caught up to metal for peak temperatures.

OTOH, thermal resistance Junction to case is a whole 'nother story. A metal can will transmit heat from the junction to an external heat sink far more effectively than a plastic package. Plastic power transistors use a familiar metal tab to help conduct heat from the junction to an external heat sink.

Back in the early days of plastic power devices I killed a bunch of brain cells chewing on thermal resistance calculations related to the less rigorous physical attachment of one screw power devices versus the standard two screw to-3 metal package. On paper it didn't look like plastic could ever work as a one for one (same die in new package) replacement for metal. I figured a roughly 3 for 2 device count to keep peak junction temperature below 150'C.

Not only did plastic work better than my calculations suggested, but forget about even one screw with spring clips providing suitable attachment force for adequate heat transfer. Spring clips are far more factory friendly than screws, that must be torqued precisely, etc.

These days this is mooted by class D switching topology that eliminates most of the massive output stage heat dissipation. Class D required years of development in the switching devices to meet current/voltage/dissipation requirements to perform the entire job in one pair of switching devices (class D amps don't parallel output devices well). 

JR