On Wed, 7 Oct 2020 19:49:14 +0100, Roger wrote:

On Wed, 07 Oct 2020 10:51:22 -0700
Jeff Liebermann wrote:

On Wed, 7 Oct 2020 16:53:26 +0100, Roger wrote:

Hi, I'm hoping that someone out there will have some info on an
ON Semiconductor 5105FA

Not exactly what you were asking:
https://www.onsemi.com/products/discretes-drivers/mosfets/ntr5105p
If you inscribe "5105" in the search box, you'll get a list of other
possible matches.

It would be very helpful if you would describe the package,
application, and provide a photo. I don't think you're reading the
part number or manufacturer correctly.

It's on a dashboard PCB from a Lincon Navigator, it seems to be a
one of a identical pair of switchers driving a transformer primary.
Here's an identical one to mine:

http://www.tehnari.ru/f39/t256954/

Well, that certainly is a readable ON Semi part number. That package
is a TO-220:
https://www.onsemi.com/pub/Collateral/221A-09.PDF
with a "style 1" pinout where the silk screened ECB suggest a bipolar
power transistor. The problem is that searching the ON Semi web pile
yields a clock generator and a tiny SOT-23 MOSFET, neither of which is
available in a TO-220 style case. There is such a thing as a 2N5105,
but it's an ancient low power JFET in a small TO-72 can.

Dead end, I guess. Back in the stone age, I would have taken the
possibly matching device, put it on a transistor curve tracer, and
tried to deduce the device characteristics. There daze, there are so
many different transistors, that such an exercise would probably be
futile. I suggest you try to find a repair shop that refurbishes
automotive electronics.
https://www.google.com/search?q=lincoln+navigator+refurbished+dashboard+m odules
or buy something from your neighborhood chop shop (used auto parts
dealer).

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558