MRF 255 Transistor.

[Raverrst]

Hi all, as in title I’m on the hunt for a Mrf 255 transistor, hens teeth I know! Has anyone got a known possible reliable supplier or know of a suitable equivalent, I’d even consider a good working used transistor if anyone has one.

Many Thanks for any help..

[ANDREWB]

Hens teeth? Dinosaur feathers, more like. Motorola stopped making things like these years ago, There will be plenty on a "well known" auction site, but will all be fakes.. Think you are bu**ered my mate.

[Raverrst]

It’s abit like it I know, There must be a equivalent out there??

[lbcomms]

The SM724 Polyfet is a very close replacement that should only need a change to the gate bias voltage - we got some from RFparts in the USA about 5 years ago. The 255s were used in the first gen "dc to daylight" Yaesu mobiles (FT100D?) sold in the early 2010's sometime, we replaced a blown pair with SM724 devices. If you are not in the USA, you'll need to use a shipping agent, RFParts do not sell to non-US addresses.

Vague memories of that repair being a bit of a challenge to get clean, a spectrum analyser good to the third harmonic of the radio it's in (in the case of the Yaseu, that would mean 1.5GHz) would be essential.

The MRF255 was discontinued as it contained lead, and therefore not be used in products sold in the USA or Europe that had to be ROHS compliant...

[Raverrst]

Thanks for the info, I’ll definitely look into that, radio in question is a Alinco dx 70.

[lbcomms]

Never seen one here (Alinco not a huge name down here in Oz), but similar to the Yaesu. Just checked the RFparts site, they still have the SM724.

[26mb04]

Try Knights, silicon ark, etc.

There is a company, somewhere, who will make batches of obsolete transistors. Unfortunately they aren't cheap either, and they tend not to make many. If I can remember the name I will update this post.

Stay away from e-bay, most will be fake.