05-13-2008, 07:01 PM
In early Philco books, I see the characteristics are slightly different between the XXL and the 7A4. Later books list them with identical characteristics. Like Randel, I have some XXL/7A4 branded tubes in my 42-350. You will not notice any difference. XXFM is identical to 7X7 so no problem there. FM1000 is unique and nothing replaces it. Another Philco equivelant is 14AF7 and XXD.
I built an FM converter off of Chuck's website. The pre-war Philco FM sets are just so-so performers. There is no limiter stage so they are sensitive to noise but it is neat to hear them play.
Fred
I built an FM converter off of Chuck's website. The pre-war Philco FM sets are just so-so performers. There is no limiter stage so they are sensitive to noise but it is neat to hear them play.
Fred