rfc@briar.philips.com (Robert Casey;6282;3.57;$0201) (08/09/89)
As you would expect, just like the ham radio synthesized trasncievers,
synthesized stereo recievers can have some simple modifications done. (I
assume that you're handy with a soldering iron, and knowledgable of CMOS
digital circuitry. Like avoiding static discharge into the chips, etc!)
I have an Akai AAR32 stereo reciever, which is a synthesized tuner for AM and
FM. In the service manual (which you should always get before you consider
doing anything inside), it describes two other recievers, the AAR22 and 42.
The 42 has all the features (random tuning and 10 presets) and the 22 has the
least features (no random, and 6 presets). My set, the 32, has no random and
8 presets. All these sets use the same comtroller chips, so all you need to
do to get all the features is add some push-buttons. I put mine on the back,
as I couldn't figure out how to add them to the front without it looking ugly!
What to do: for the AAR32:
first, get the service manual!
turn off the power!
then:
-Do not remove any screws that mount the pc boards to the chassis, or you may
end up fighting with buzz noises (comes from the digital stuff).
-get some momentary contact switches (I used a push-button, and a momentary
contact center off double throw toggle switch), use normally open.
-find a good place to locate the new switches (I removed the AM antenna
bracket, and mounted the switches in that hole.)
-plan a good route for the wiring of the switches (like avoiding going near
audio signal lines, especially phono inputs, and AM and FM inputs)
(shielded multiple cable would be wise)
-find on the controller board J5 and J9
-wire the random push-button across pins 1 and 6 of J5 (what I did was solder
the new wires to the ends of cables going to J5 and J9 on the controller board)
-wire the common of the momentary contact toggle to pin 6 of J9
-wire the "0" side of the momentary toggle to pin 3 of J9
-wire the "9" side to pin 4 of J9
-reconnect the cables
-inspect your work, make sure you're not shorting out something, etc.
connect the power, AM and FM antennas, and speakers or headphones.
Turn on the power. You should hear the station you were listening to
last. Hit one of the old presets, and you should get whatever you had
programmed for that preset. Ok, so that seems to work, right? Tune
another station in random access style like this: Press the random
button. The tuner will mute and the frequency display's first digit
will flash, and the other digits will be 0s. Type in the freq of the
station with the preset buttons. The last digit is always a 0, don't
type it in. The tuner should take a second to find that station, and
then you should hear it. If you type a not valid frequency, like 144.7
Mhz, the controller won't try to tune it, but will make the freq
display flash. Hit "random" again, and type a valid freq. Then you'll
get that station. You'll find that the controller puts the reciever in
"auto scan" mode if you make this error. Hit "manu scan" if you want.
You can program the 9 and 0 buttons as presets, like the other presets.
For the AAR22 (which I did not try, I don't have one. The following I got by
looking at the diagrams in the service manual):
-do the steps for the 32 above, except don't do the steps wiring the switches
to J5 and J9, as these are different on this set.
-for the "7" button: wire pins 3 and 8 of J6
"8" pins 4 and 8 of J6
"9" pins 1 and 9 of J6
"0" pins 2 and 9 of J6
"random" pins 4 and 9 of J6
Finding a place to mount these new buttons may be a problem. Don't forget
about static discharge if you decide to make a wired remote box. You'd be
wiring direct to CMOS circuitry, which is easily ruined by static from carpets
in winter.
Disclaimer: Proceed at your own risk! So be careful when you do this, like
avoiding static (use grounded soldering irons), shorts, solder spashes, etc
73 de WA2ISE