Re: [Amc-list] Testing Old Radios

[Tom Jennings <tomj@xxxxxxx>]

-- Mark Fox <Mark.Fox@xxxxxxxxxxxxxxx> wrote:
> I was trying to test out some old AMC/Motorolla radios before putting
> them on Ebay.  These were being tested on a work bench.  While the radios
> turn on (The lights come on within the radio), I get absolutely no sound.
> I have the radio attached to a 12 volt power supply, the antenna plugged
> into the radio and the speakers attached to the radio.  Is there anything
> I am missing - such as do I need the antenna and/or speakers grounded to
> the radio?  If not, then I have a couple of dead radios.  Anyone know how
> much voltage should come out of the radio to the speakers?  I was only
> measuring .4 volts.


Some of those old radios are very fussy about speaker impedance, and tend 
to be high impedance (20, 16, or newer ones 8 ohms). Most current speakers 
are 4 or less, it could pop the final audio transistor.


Make sure that your 12V supply remains 12V when the radios are on -- they 
draw a lot of current (2A or more) and "wall wart" type supplies wont' 
work. You need a "battery eliminator" supply or a car battery. They also 
rely on clean, quiet battery to work right.

With the volume cranked to 11, even with no antenna you should have a faint 
hiss at least. I find they work with not much antenna and no ground (I use 
4 feet of wire) but only get local stations that way.

With an antenna in , real 12V power, volume cranked to max on the correct 
speaker, tuning from 530 to 1600 you should find SOMETHING loud enough to 
hurt your ears...


> Mark Fox
> Flextronics
> 1000 Technology Drive
> West Columbia, SC 29170
> Mark.Fox@xxxxxxxxxxxxxxx
> +1 (803) 936 5976 Office
> +1 (803) 397 7814 Cell
> +1 (803) 216 1347 Fax
> Creating value that increases customer competitiveness
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