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Vintage Philco AM Radio Restoration

brickbricker

  Welcome to my first blog post! Constructive criticism is encouraged. For my first post here, i will be talking about an old AM radio my dad gave me to fix up. It works, but the sound isn't that great. Sure, you cant expect hi fi from such an vintage piece of electronic history, but I believe the sound quality could be better. I don't know the model number off the top of my head, but i will post it in the next blog entry. I do know it is a philco radio, and a part diagram is on the inside of the unit. I also have reason to believe it was repaired. If anyone can help me by finding more details about the radio, it would be a great help. Here is a picture of the unit: http://bit.ly/RYXTwy Again if anyone. Can help with identification that would be great! Stay tuned for the next blog post!

  • You should google 'all american 4' and 'all american 5' this device uses six active devices, but I bet the extra one(s) are for the power conversion that was necessary to get this device ready for line operation.

  • I don't seek to be alarmist, but there is this generational thing where most electronics nowadays is powered by 5V or less and current draws are low, so people are wrongly sanguine.  I'm just saying, play it safe.  The potentials here aren't that great, and mostly imply pain rather than mortality.  I went hiking at Garden of the Gods Monday, where a young girl died Tuesday.  I still wouldn't advocate closing nor guard-railing of the facility.  I certainly advocate caution when dealing in dangerous things. I just bought some antique equipment from a guy who touched the HV of an old school TV when he was a kid.  30KV.  It shot him across the room, he was in hospital for a week, but he recovered fully.  When working with high potentials, make sure your work area is very neat.  It would be tragic to suffer secondary issues involved with landing.  Just remember the joke about the physicist who implored the young man not to jump off the Empire State building:  "Don't!  You have so much potential!"  Every time we double the potential, we increase the danger by a factor of four.

     

    The big caps should sit with a jumper across them for awhile before you take them out to replace them.  Don't wanna get shocked?  Don't be lazy and operate your device open-frame.  You can take out your tubes and put them on a tube-tester. replace them, screw the chassis back together, then power-up.  That your device sorta-works now indicates that not too much diagnostic intervention will likely be necessary.  If you are patient, you can use clip-probes to your volt-meter and power-up remotely.  The RF front-end probably cannot be directly monitored anyway, as the energies used there are so slight that the perturbation of the observer would be insuperable.  I think you should check for a torn speaker cone.  Disposable rubber gloves help, they have, typically, a real high dielectric, but don't protect against punctures to the glove.

     

    Also, clean up this device with appropriate solvents and compressed air at no more that 15psi. I knew a TV repairman who insisted upon cleaning everything before allowing himself to have a diagnostic thought, as so many of his client's devices remitted upon clean-up.

     

    Do you understand superhet and AM detection?

  • in reply to D_Hersey

    The other option I've seen used is a light bulb in SERIES with the active.

    Obviously judging the size of the appropriate light bulb is important, and it may be better to use two 100w bulbs in parallel.

     

    The idea is that if there is a short, or other fault, the worst that happens is the light bulb illuminates.

    Its great for fixing switchmode supplies.

     

    The isolation transformer is also a very good idea.

    Mark

  • in reply to D_Hersey

    oh boy.... you've made a very good point there, i will have to ask the family electrican for advice. I have" touched HV "before, but something was preventing me from getting the full brunt of it. i think i will have to put this one on hold. Thanks for the advice though.