REBUILDING JOHNSON & other gear

[Richard Arland, W3OSS]

I have to echo Dee's remarks, especially about the resistors, and double especially (hmmm..is that a word?) when dealing with Hallicrafters gear. 

I have restored over 30 Halli receivers/transmitters/transceivers over the last 15 or so years and in almost every instance, when dealing with 1950-60s gear, the majority of the resistors were out of tolerance sometimes by as much as 300%. 

The most unique thing happened while restoring my last SX-71: after replacing almost every carbon comp resistor on the chassis, and better than 80% of the caps (ceramic & electrolytic) it fired up fine. I then put the HP sig-gen on it and had virtually NO adjustments to make to align it! This is the first time that this ever happened to me. I was amazed! 

Does anyone have information on crystals? I understand that they can shift Fo with age? This would lead me to believe that any of the first generation synthesized radios (CBs, MilCom gear like the PRC-74Bravo, etc) could be a real pain to get aligned. 

73 Rich W3OSS

  Dear AM'rs
    I rarely make suggestions but.... ANYONE overhauling BA's should keep in mind, these rigs are many years old. And even though the capacitors look ok is being mislead & lots of frustration. My shop policy is (especially Johnson) CHANGE OUT ALL CERAMIC BYPASS CAPS & check every resistor for value. 

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