[Elecraft] K2: No audio after fitting KDSP2

[Matt VK2RQ]

Forgot to mention, do your audio tracing with the K2DSP and dummy rework boards removed, in order to isolate the later AF stage from the rest of the radio.

73, Matt VK2RQ

> On 28 Apr 2015, at 6:50 am, Matt VK2RQ <matt.vk2rq at gmail.com> wrote:
> 
> I'd start with the audio stage. Inject an audio signal into the AF amp and see if you get anything out. Check the voltages around U9 to make sure they are ok. If the AF amp is working, then step back and check out the muting circuit by injecting your audio signal just before. If you have an oscilloscope, this may be helpful in seeing where the signal is being lost. It may be a dry joint that you disturbed when you were working on the radio. It’s also possible a component has failed (eg. C27) and is shorting out the signal. Or it may be U9 itself has failed. The AF circuitry is fairly simple, so shouldn't be too hard to track down.
> 
> 73, Matt VK2RQ
> 
>> On 28 Apr 2015, at 5:41 am, Mick Hall <mickchall at yahoo.co.uk> wrote:
>> 
>> Hi.
>> 
>> My K2 has been working fine for a few months now and I was finding the background noise that gets pulled in very tiring, so I decided to buy the KDSP2 DSP filter.
>> 
>> The build went fine and so did the install. After turning on the K2 I checked that the menu settings were all there and followed the manual. I then realised I did not have the  speaker plugged in, so I plugged it in while powered up. I got a loud pop through the speaker, then silence.
>> 
>> I thought that perhaps I had missed a menu setting whereby I would have to enable the KDSP2 but couldn’t find anything so obvious.
>> 
>> I built the K2 with the Rework Eliminators installed, so I removed the KDSP2 and placed the header back in place and still I had no audio. I have also removed my KSB2 and KIO2 module so now I am back to the bare K2, but still I have no audio.
>> 
>> I can only assume that something failed when I plugged in the speaker whilst still powered on.
>> 
>> I have tried injecting a signal in with the Elecraft wideband noise generator and the cheap and dirty signal tracing document but with the headphones plugged in and the AF and RF gain at full, I hear nothing at all at any point, only a very faint hissing. Although the signal does register on the S meter.
>> 
>> I have also followed the troubleshooting in the manual and gone through the full alignment procedure as recommended but still no luck.
>> 
>> Could someone help with a place to begin to try and track down the faulty component or components.
>> .
>> Many thanks
>> Mick
>> 
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