Solving the TO3 direct replacement and obsolescence problem

Over the past years I have been faced with a continual problem during repair and refurbishment of older Transistor and FET based power amplifiers and power supplies, so much so that in many cases really rare equipment sometimes does not get repaired and we think twice before taking them on for full refurbishment. This is due to the obsolete nature of the TO3 and its derivative (TO204AA) Transistor, FET and Regulator packages.

Over the past year we have developed a TO3 carrier that will carry a standard D-Pack device and mimic exactly the foot print and mechanical considerations of the TO3, we have found that there are many equivalents to the old TO3 devices available in D-Pack. One good example is IRF244 which can be replaced with a IPB600N25 3G OptiMOS at a cost of US$1.32 (ZAR18.02) and about US$10.00 (ZAR135.00) for the carrier and assembly.

How it works:

We machine a TO3 body from brass flat-bar, Nickel plate the machined housing, find the equivalent D-Pack device, solder it into place in the TO3 carrier housing, connect the pins with wire leads, place it into a precision machined  mold and fill the housing with a 125°C polyurethane electronics potting compound.