Headphone jack problem now solved, but it wasn't anywhere near what I thought
it was going to be, and it was a lot more complex than I thought it would be.
I took apart the entire front panel to reach the front headphone jack,
de-soldered the jack, took it apart, cleaned it up, and re-installed
everything. To my disappointment it did not change a thing. Time to break out
the O-scope.
After about an hour of probing around and reviewing the schematics, I traced
the "end" of the working audio chain to the audio amplifier. The audio is
supplied from the main board on the front panel, and was reaching the amplifier
on pin 8, but there was no output on pin 2, which routes the amplified audio to
the small circuit board mounted at the rear of the chassis, which then
distributes the audio to either the internal speaker, or the external speaker.
To be clear, this audio amplifier (TDA1013B) was NOT the problem. The problem
turned out to be the lack of voltage supplying the chip. It was getting around
2.5mV, where the voltage should have been closer to 12 (13.8V minus whatever
the 3.3 Ohm resistor drops it to). I traced the voltage path to the main
board, where Ten Tec conveniently provides testing pads for the different
voltages needed on this board. All of these pads checked out, with the
exception of one 13.8V pad.
To find out why I had to remove the main board. (If you have to do this, take
care of the small ribbon cable that connects the main board to the LCD panel.
It's small and the connectors are delicate.) After removing the board I
IMMEDIATELY found the problem without even having to look hard. There was a
bulging capacitor and about 3 inches of burned trace that provides the 13.8V to
the 2-prong plug (#43 -- J905/MT2), which in turn powers the audio amplifier.
The repair was relatively easy--replace the 470uF capacitor and re-create the
trace with some enameled 28AWG wire. I followed the original path of the
trace, soldered both sides, and glued the new wire to the board on both sides
where the trace ended. Re-assembled, and was ecstatic that I now had my audio
back.
As to why this trace gave way, I have no idea. That is a mystery yet to be
solved. I just hope that whatever caused it doesn't happen again.
________________________________
From: Marcus Florido
Sent: Wednesday, February 16, 2022 12:04 AM
To: tentec@contesting.com <tentec@contesting.com>
Subject: Headphone jack problem
Hi guys,
After a little work I have my Orion II in (almost) full working condition now.
Nothing a little time and solder couldn't fix. However, I have a problem with
my audio. It appears that my Orion II thinks that headphones are plugged in no
matter what. I get no audio from the speaker or the external speaker jack. I
do get audio from the headphones, though, and the little headphone icons are
present on both receivers in the display no matter what. Master reset does
nothing.
Before I go digging into the front panel, has anyone ever had this condition
before? Any tips or tricks?
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