Re: AMC Radio Testing

> +12V onto the power wire.  BTW, if there is an ORANGE wire coming out (like
> on the 67-69 radios) that's JUST the light, ignore it.
>
> Connect ground to the metal case.
>
> A wire shoved into the center hole of the antenna plug will work as the
> antenna or you can use a real antenna.  No antenna ground necessary.
>
> There should be a two wire plug hanging off the radio (green and brown wire
> probably) hang a speaker across those two wires and your all set. Turn on
> the radio and see if it works.

Ayup.

One caution -- on the early transistor radios (63 up) you must use
ONLY an 8-ohm speaker. DO NOT use a 4-ohm speaker (which are more
common these days). The power transistor (2N176, diamond-shaped,
usually towards the front, often gold-colored) is primitive and
will overheat and die if you use 4-ohm and crank the volume. You
might "get away with it" but I wouldn't.

Also don't short that big transistor's case to the chassis, or
battery.  It won't shock you or anything, but it's got power on
it.

The physical size of the speaker doesn't matter, it's the
impedance (8 or 4, etc) that matters. If you somehow found a 16
ohm speaker, it would work, but probably not be loud and maybe
raspy.

The early AM only transistor radios -- how do I say this nicely --
suck.  Seven (7) transistors! Not atypical or anything of the
era, but not exactly high quality sound or reception.

Reception might suck also with just a wire or antenna on the
bench, but don't worry 'bout that. If it works at all it'll be OK
in the the car.

ANd don't turn any of the screws in the junk inside; the radio will
need a complete alignment if you do that.

When you install the radio, you do need to adjust the antenna trim
capacitor thingamabob on the back of the set (sometimes via a hole
in the front). On back, it's a little metal knob near the antenna
jack; the procedure is to tune to a weak station near the top of
the dial and adjust the trim for best reception. It can make an
INCREDIBLE difference. You do this on the car when you install the
radio or a new antenna.

I have the factory service manual for the early Motorola AM
radios, schematic and all that. I can scan and put on the web if
anyone needs it. Technical service info only.

Tom Jennings <tomj@xxxxxxx>