[Elecraft] KX1 speaker output with superimposed oscillation

[Francisco Barros]

Hi to all,

The scope shows a superimposed high frequency oscillation just on the 
negative peaks of the audio signal.
It produces a distorted and annoying audio when the signal peaks, specially 
when listening a loud station on the external speaker.
This happens when the volume is close to or at maximum volume. I fails just 
with Panasonic RP-HT60 20 Ohm headphones and external 8 ohm speaker (both 
work fine with my K2).
It works OK with Panasonic earbud type headphone and with an external 8 Ohm 
load !!.

I have re-check every component all around LM386 audio amp: values are OK, 
soldering fine.
It doesn't matter if the KX1 is working with external power (7-12 V) or 
batteries.
At 12 V the RX current drain is about 35 mA (minimum volume). I raises to 71 
mA at maximum volume with the external 8 Ohm resistor, and 75 mA with the 
external 8 Ohm speaker.

Hope somebody can help me. Thanks in advance.

73,
Paco Barros

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