01-05-2006, 05:18 PM
Working against the clock, I tried my best to complete a Model 38-3 on New Year's Eve. Unfortunately, the radio didn't cooperate - upon initial power-up, it would only work on the first SW band - no AM, no upper SW band.
So I set it aside, and returned to the set a couple days later.
Fortunately, I happened to have a 38-3 parts chassis in the "archives." I pulled its RF unit, disassembled it and went over it with a fine-toothed comb, so to speak. Everything that could be replaced, was replaced (resistors, paper AND mica capacitors, wires). I checked every coil and all had good continuity. I did find a high-resistance leakage to ground which turned out to be an interconnecting wire; it, too, was replaced.
(Yes, all paper caps and some resistors had been replaced in the original RF unit, but I admit I got in a hurry and didn't check the coils for continuity as I should have.)
I pulled the faulty RF unit from the client's 38-3 and installed the other one - upon initial power up, Pawn Vanity's voice started coming out of the set's speaker. Success! It works on all three bands. Now for an alignment, and to see if the magnetic tuning works. Still needs a new dial scale, new grille cloth, and repro decals. But at least the worst is behind me now on this one.
Although this RF unit is a bit easier to service than some others I've worked on, I still think David Grimes (the Philco engineer responsible for the 1937-38 "Unit Construction") should be brought back and forced to spend every day, for many, many years, rebuilding several of his not-so-wonderful inventions.
So I set it aside, and returned to the set a couple days later.
Fortunately, I happened to have a 38-3 parts chassis in the "archives." I pulled its RF unit, disassembled it and went over it with a fine-toothed comb, so to speak. Everything that could be replaced, was replaced (resistors, paper AND mica capacitors, wires). I checked every coil and all had good continuity. I did find a high-resistance leakage to ground which turned out to be an interconnecting wire; it, too, was replaced.
(Yes, all paper caps and some resistors had been replaced in the original RF unit, but I admit I got in a hurry and didn't check the coils for continuity as I should have.)
I pulled the faulty RF unit from the client's 38-3 and installed the other one - upon initial power up, Pawn Vanity's voice started coming out of the set's speaker. Success! It works on all three bands. Now for an alignment, and to see if the magnetic tuning works. Still needs a new dial scale, new grille cloth, and repro decals. But at least the worst is behind me now on this one.
Although this RF unit is a bit easier to service than some others I've worked on, I still think David Grimes (the Philco engineer responsible for the 1937-38 "Unit Construction") should be brought back and forced to spend every day, for many, many years, rebuilding several of his not-so-wonderful inventions.
--
Ron Ramirez
Ferdinand IN
