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Valve/tube car radio AM to FM conversion ideas?

Discussion in 'Electronic Repair' started by N_Cook, Jun 5, 2008.

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  1. N_Cook

    N_Cook Guest

    For appearance and modern day use in a vintage vehicle.
    That is adding an FM IC inside somewhere rather than RF converter plugged in
    aerial socket.
    Assuming there is somewhere around the volume control to switch out the AM
    and switch in an FM IC o/p audio . How to secrete that switch and a step
    through the band switch as channel changer.
    Maybe possible to change the LW/MW switch to MW/FM and if some part of the
    dial scale is flexible then hide a switch behind that.
    Any other ideas without affecting the external appearance of the original?
  2. If you want someone else to work on your radio you might check with
    Gary Tayman in
    he does these conversions on a regular basis, and is a frequent poster
    over there.

    Also If you are in Canada, you might contact Larry Wood I think he has gone into doing something similar as

    In consumer radio restoration , replacing the innards of a tube radio
    with a bunch of IC's is kind of frowned upon, as most of us strive to
    restore the radios instead.
    What I am saying is that you do have a choice, if the car is stock ,
    personally I wouldn't go this route unless I couldnt' fix the
    orrigional radio for some reason, but it is a personal choice. I have
    an old volvo with an AM radio that was a transistor set, and my choice
    was to plug a FM tuner into the antenna , which the radio recieves on
    AM at a set frequency. That way I still can have the stock radio in
    place and tuck the FM unit away . If the car is old enough to have
    tubes, it will also have a vibrator and solid state vibrators are
    available. Either Gary or Larry might be able to give you the option
    of restoring the set for you as well if that is what you want. any old
    radio will probably need to be re-capped and alligned to work right.

    gongrat likes this.
  3. N_Cook

    N_Cook Guest

    I should have said retaining the original in working order but just adding
    in somewhere, the guts from one of those matchbox size fm radios. No display
    just 2 buttons on/off and channel step and an earpiece. Maybe requiring some
    buffering or something to drop it in the existing (mono of course)
    amplifier. Preferably no holes drilled through the front pannel.
  4. Engineer

    Engineer Guest

    Surely the real fun is to use the FM to AM converter Rx so that yiou
    can listen to the "old 'un". I use my AMT3000 Tx the same way at
    home. Feed it with a s/s FM tuner and listen on one of several
    refurbished AA5's and AC-only sets to "exercise" them - the converter
    tube, IF amp and det/AF and OP tube all a-pumpin' away! <g>
  5. Gary Tayman

    Gary Tayman Guest

    You have just described the FM Module exactly! Just one fly in the soup --
    these haven't been available for several years.

    I do stereo conversions on these radios. Vintage Wireless in England
    (mentioned elsewhere in this thread) also does these, hopefully quicker and
    for less money than it would cost to ship it to me.

    All of these products originated at a place called Antique Automobile Radio
    in Palm Harbor, Florida. Dan Schulz, the owner, began as simply a dealer
    who repaired old car radios. As replacement vibrators became scarce, he
    started making solid state replacements. Then, as customers were asking for
    FM, he designed an FM Module that would fit inside the radio. Eventually he
    designed a stereo PCB, and the popularity of these soared -- to the point
    where only two dealers in the entire world were still asking for FM Modules
    (me and one other). They were finally discontinued. Now Dan is making
    reproduction radios for certain cars -- radios that look exactly like the
    original, but are complete new radios with the AM/FM stereo technology.

    The FM Module was a neat little device. It was a tiny PCB with an FM tuner
    built onto it. Connections were to the antenna (with a 6.8 uH choke for
    separation), to the grid of the converter tube (or to the LO coil for
    transistor sets), to +12 volt power, and to the top of the volume control --
    and the wire going to the volume control is rerouted to the PCB.

    Switching is done by turning the radio off and immediately back on. PCB's
    could be set up for FM first, or AM first. In AM mode, relay is off and the
    AM audio is connected to the top of the volume control. In FM mode, the
    relay is energized, and the FM output is fed to the volume control. FM
    tuning is performed with the radio's original tuning knob -- it uses the
    radio's LO frequency to tune FM.

    This Module was actually quite a performer, and a very likeable product.
    The one and only "bug" of sorts was the fact that it could drift, and the
    amount of drift varied with the radio model. The radio's LO drift is
    usually not enough to notice, but when multiplied for the FM frequencies it
    could make a difference. Even so, it still was a nice product.

    At one time, about a third of the radios sent to me wanted the FM Module
    installed. It was also handy for early Bendix, and early Delco AM/FM radios
    with awful FM front ends. If repair of these was difficult or impossible, I
    would simply disconnect the FM entirely and install an FM Module to the AM
    coil. The only thing customers ever noticed was that their radio performed
    better than ever in FM!

    The day the FM Modules were discontinued, I discontinued offering service on
    car radios. I've since offered service again on radios, but not on AM/FM's.
  6. Jim Adney

    Jim Adney Guest

    Just curious, would it be possible for you to duplicate those modules
    yourself, or did they require that NLA FM IC?

  7. Gary Tayman

    Gary Tayman Guest

    These modules did indeed use specialized IC's, which were part of their

    AAR had just introduced a new version of the Stereo PCB, which had a digital
    tuner. It worked fine on the bench but went crazy in the field, so Dan had
    to quickly redesign it. It so happens this "quick redesign" was by far the
    best version to date, and sales suddenly went through the roof. However
    during this time Dan was going through some family problems, and if that
    wasn't enough the IC's used in the FM Modules were discontinued. So
    suddenly the FM boards became unavailable.

    Dan eventually managed to redesign a new FM board, and this was cool as it
    was the size of a postage stamp. But it also had a bug. I was given about
    three or four to experiment with; I think one actually made it to the field
    and worked (in a Mopar 802) but the others are still here. Dan eventually
    decided that, with sales of Stereo PCB's going wild, and with waning
    interest in the FM boards, he scrapped the project.

    The remaining FM Modules went pretty much to experimenters, some of which
    installed them in home radios, and they worked. Someday when I have lotsa
    time I'll tinker with the ones I have to see what happens. Installation
    isn't hard, except it needs 12 volts DC for power, and the radio must have
    an oscillator (meaning I can't put one in my AK-60 -- darn).
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