View Full Version : Propeller Demo board Rev F restarts anytime an Audio Plug is inserted into audi

02-20-2007, 02:46 AM
I have a rev f prop demo board that restarts anytime a 1/8 " TRS plug is inserted into the audio out jack. The same thing happens even when a "fresh" (no connections) plug is inserted. I originally thought that the jack had a "sense" lead and the behavior was normal. I took a look at the schematic which shows only the typical connections (left right and ground), but when examining the board, there are actually 4 pads soldered to the jack. (one maybe just an anchor?) Anyway, is this behavior normal and if so, why ?

If you insert the plug very quickly it occasionally won't restart, also the same results occur when "disconnecting" the plug.

Mark S.

02-20-2007, 02:56 AM
Sounds like something is shorting when that plug is inserted, killing your power supply. Scope the power supply when you
do the insertion.

02-20-2007, 04:09 AM
Oh Yes, that is my point, a TRS Jack (tip,ring,sleeve) does short during insertion but there should be no + - potential at that jack !


Mark S.

Mike Green
02-20-2007, 04:14 AM
You're right. There should be no +- potential at the audio output jack. There's not supposed to be any such potential, therefore you may have a defective board or defective headphone amplifier chip. I suggest you contact Parallax's support department when they open tomorrow and arrange for a replacement.