I'm looking for suggestions (preferably other than "Trace the internal
wiring, Idiot!" or "Next time, buy a radio with a manual, Idiot!) on how
to determine the pin-outs of a Delco AM/FM radio "about 10 years old"
that came with NO manual and has NO identification other than MTD-1316
stamped into the metal on the rear.

On the rear, in addition to the standard antenna jack, there is one 13-pin
recessed (mostly?) male connector (I do NOT have the matching connector)
for which (I'm hoping) someone will recognize the pin-outs. If =
represents a horizontal flat "pin", o represents a slight dimple (but
NOT a hole) in the plastic which holds the = pins, 0 represents an
actual hole which goes through the plastic, and everything else represents
the shell and keying plastic, the plug kinda looks like this:
___________________
/ = = = | 0 | = = = \
| o o o o o o o |
| = = = | = | = = = |
+-------------------+

I'm NOT going to try to "draw" an actual ASCII picture of the front of
the radio, but it has the following controls sorta in the indicated
positions:
+----------------------------+
+---+ TREB SET | |
|PWR| | |
+---+ BASS AM-FM | |
| |
BAL +----------------------------+
UpArow UpArow ==== ==== ==== ==== ====
VOL FADE TUNE
DnArow DnArow SEEK RCL SCAN
========= ======= =========

CONCLUSIONS SO FAR:
* It is obviously digitally-tuned and probably has only five digital
memories for each band.
* The BALance control implies the radio has at least two speakers.
* The FADE control implies the radio has four speakers.
* Because the PoWeR switch BARELY depresses and does NOT have two
distinct positions (instead, it has a plastic-covered hole probably
for a pilot-light to show through), the switch probably controls
some electronic circuit to turn the radio on and off.

GUESSING:
* Each group of three = = = pins probably belongs to one speaker,
and an internal examination may show the middle pin is ground.
* The HOLE in the top row EITHER
* doesn't have a connector hidden behind the plastic (in which
case the chassis will be GROUND) OR
* if there is a hidden connector, it will be GROUND (like a U-GROUND
outlet) (My reasoning: one would NOT want the matching connector
to have a hot 12-volt pin sticking out like a sore thumb!)
* The pin immediately below the hole will then be for +12 volts.
* Since all 13 pins are now "accounted" for, there probably is no
antenna-control power wire.

I am definitely open to other possibilities!

--Myron, W0PBV.
--
Five boxes preserve our freedoms: soap, ballot, witness, jury, and cartridge
PhD EE (retired). "Barbershop" tenor. CDL(PTXS). W0PBV. (785) 539-4448
NRA Life Member and Certified Instructor (Home Firearm Safety, Rifle, Pistol)