[Elecraft] K3 - No speaker output

[Joe Subich, W4TV]

> Elecraft now has an Audio Protection Assembly circuit board, Part
> Number E850506 for $2.36 plus shipping.

The Audio Protection Assembly replaces the 470 uF output capacitors C2
and C3 on the RF board with a series combination of a 1 Ohm resistor
and 470 uF capacitor.  The same thing can be accomplished by replacing
L13 and L16 (surface mounted "beads") on the KIO3 Audio IO Board with
the appropriate size 1 Ohm surface mount resistor (or potentially even
a leaded part).  The advantage t modifying the KIO3 Audio IO Board is
that it is not necessary to disassemble the K3 (and remove sub R and/or
2M transverter) to gain access.

Note - the bead to resistor modification is my own adaptation and not
recommended by Elecraft.

73,

    ... Joe, W4TV


On 1/14/2014 12:21 PM, Dave Hachadorian wrote:
> The speaker amp is U1 on the DSP Board.  The IC is an LM4950TS. The pins
> are very closely spaced, too close for me.
>
> Elecraft now has an Audio Protection Assembly circuit board, Part Number
> E850506 for $2.36 plus shipping.
>
> Dave Hachadorian, K6LL
> Yuma, AZ
>
>
>
> -----Original Message----- From: Stewart
> Sent: Tuesday, January 14, 2014 9:36 AM
> To: Elecraft Reflector
> Subject: [Elecraft] K3 - No speaker output
>
> My K3's speaker audio seems to have gone West. Audio out of the phones, but
> nothing out of the internal speaker.
>
> It happened when I was installing a new external speaker, a DSP Desktop
> speaker
> from BHI.
>
> Having read some recent posts about the audio chip blowing up because of
> using a
> mono plug instead of a stereo one, I made sure that I used a the correct
> one.
>
> Following guidance in the K3 users manual I connected the speaker to the LH
> channel as I want to use my headset in stereo.
>
> I also took the covers off and checked for the modification involving
> 470ohm
> resistors. That mod was in place OK.
>
> I switched the K3 and the speaker on and got audio from the speaker.
> However,
> when I advanced the AF gain on the K3 to about 12 o'clock there was a
> pop and no
> more speaker audio from the K3.
>
> I have checked the BHI speaker with another rig and it works fine, so my
> K3 has
> developed a fault.
>
> I can't believe how sensitive it is to damage in the audio output,
> particularly
> with the care I took to try and avoid this sort of thing happening....
>
> As I am quite OK with SMD's I would appreciate advice on what to change,
> where
> to get it and how...
>
> Not a happy bunny !
>
> 73
> Stewart G3RXQ
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