Hi. Does anyone know what part the transistor SRF772 really is? They are in a TPL5010 RF amplifier. SRF772 is mentioned nowhere on Google or Bing. I was told that more than likely, the transistor might have that weird designation because when TPL bought a certain amount of these transistors, Motorola stamped a different part number on them for that specific brand, so when people needed a replacement transistor, they would have to go to TPL for the part, and not Motorola, to protect the OEM agreement.

It’s a neat little amplifier, designed to work from 21-30Mhz, class AB, so it can work on AM, FM, CW, SSB. 60 watts carrier/140 PEP. I use it with an old Realistic (Radio Shack) HTX-100 transceiver on SSB on ten meters, which gives it a good boost from the radio’s max output of around 20 watts. Thanks for any help.>The TechForum Cross Reference category is for parts that Digi-Key does not sell or parts that have gone obsolete. Our Engineers and Techs have reviewed the specifications for these parts and made a recommendation for a replacement. Please review the suggested part to ensure it will work for your application.

Hello Adam,
Thank you for your inquiry and welcome to Techforum. I am sorry the part does not come up in our system. When I enter SRF772 into Google it does have a few hits from other forums.

Your Reference number is # T4280339.

I couldn’t find anything in old cross reference books or searches.

BTW it is very rare for any product sold in small volumes like an RF amplifier to have custom marked parts to prevent inexpensive repair. It is a very costly option in low quantities and the whole benefit can be had for far lower cost by simply removing the makings from standard components (that was very common in the last century).

More often than not, an unidentifiable number is because it’s a semi-custom or full custom part. Often the part will have only a few specs different than the standard part upon which it is based, Frequently it is simply that additional testing was done by the part manufacturer to sort parts and allow them to guarantee one or more tighter specs than the standard part would have.

In both these cases the only solution is to either get more information from the product and/or component manufacturer (in this case I think they have both been out of business for decades), or reverse engineer the circuit.