The AM Forum

I can't seem to find a US equivalent for the BD224D transistor.

Anyone know?

mistype

BD244D

ON makes it since 2016, when they bought Fairchild.

They have the datasheet.

--Shane
WP2ASS / ex KD6VXI

listing of BD specs

https://www.futurlec.com/TransPowerSpec.shtml

Equivalent to NTE332

https://www.nteinc.com/specs/300to399/pdf/nte331.pdf

https://www.ntepartsdirect.com/ENG/CATEGORY/SEMICONDUCTORS_TRANSISTORS?gclid=Cj0KCQjwt_qgBhDFARIsABcDjOeTaqWINMsGxsYxClLlUd6H96gykIk67xw6zlaInvvXkCF81YYZF-MaAgZTEALw_wcB

https://www.electronic-spare-parts.com/descript/b/bd_244d.htm

Thanks a bunch.

Only source is Donberg...Ireland.

The "D" version is rated 160V...which is important.

Others that you reference only 100V.

After long search...found that NTE37 will work as replacement.

If the the transistor is used in a complementary amplifier or switch circuit (NPN and PNP), I would suggest also getting the NTE36 transistor.
And you might be able to go and get them locally.
44 Farrand Street
Bloomfield, NJ
https://dilp.netcomponents.com/cgi-bin/nteincsup.asp?supplier=954710&Part=NTE37&updated=3/24/2023
Don't know if they have a "buy in person" at their location. Years ago they did and the location was called "Electronic Barn" at 48 Farrand St. Solid State Inc. is at 46 Farrand St.

The transistor is used in a circuit from the transmitter output to a vintage POWER AMP.
Seems like the T/R relay in our rigs is very current sensitive...and...the T/R relay in the amp can actually 'blow out'
the rig relay.
His circuit only puts 350uamps to the rig relay.

The TRX lab gent is a 'genius' when repairing ham gear!!
Here's his video on the relay protector:
https://www.youtube.com/watch?v=j7Aw0Y_Gan4

Since you never gave us any history in this thread, this post sheds no information on what the problem was.
After reviewing a portion of the video, I see why you want the transistor. He should offer the video for sleep deprived people   :D

Interface circuits for modern solid-state radios to interface with older power amplifiers that run high keying voltages has been around since the middle 90's if not earlier.

I use the Harbach designed interface between my solid state rigs and my Heath SB-200 amps that have a -130 volt keying voltage. The design uses an Opto-Isolator design and works extremely well. MFJ and several other manufacturers and garage builders also have designs on the market.
Here's the Harbach keying interface for the TL-922/922A:
https://harbachelectronics.com/shop/kenwood-tl-922/sk-922-soft-key-keying-interface/
W8JI has also developed an universal relay line buffer:
https://www.ctrengineeringinc.com/universal-relay-line-buffer/

The problem with the simple TRX design, if that, if the transistor breaks down for whatever reason, the high keying voltage of the amplifier will appear on the delicate relay contacts of your solid-state rig and, most likely, will fuse the contacts together.

Well, I don't know what the circuit is but my reference came the latest NTE semiconductor reference.

I captured below the circuit from the you tube video. It's nothing more then a soft key T/R switch interface between a  solid state transceiver and an amp using 100 volts or more in their relay keying circuit.

OK, thanks.

I usually use a 2N6740 for those types of applications

https://pdf.datasheetcatalog.com/datasheet/mospec/2N6740.pdf


Phil