[Elecraft] K2- Sometimes no audio after switch on

[Stewart Baker]

On Tue, 30 Nov 2004 15:51:22 +0100, McNamara, Philip wrote:
> Response to Stewart G3RXQ
> I have also experienced the strange effect of no audio out after switch on.
> My K2 has been operational for about 3 months now and I have noticed the
> problem only about 4 or 5 times. I just switch it off and then back on again
> and everything is ok. Next time I will probably try to analyse the problem in
> more detail. The problem was never apparent when I completed the basic K2 it
> only became noticable after the option boards were added.
> Just for information I have the noise blanker, SSB, ANT-Tuner and DSP options
> fitted.
>
> 73 Philip DB3LMN
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Hi Phillip,

Sorry to hear about your problem. I don't know if there is any similarity with 
what I am getting.

Question:- Do you have a microphone with an in-built pre-amp that uses the K2 
+5v for it's supply ?
If so it maybe loading the 5A rail and affecting the MCU reset. Unlike many 
microprocessor circuits the K2 MCU relies on the 5V (5A) rising to +5v during a 
certain period. If it doesn't, then because the Reset (MCLR) is the same signal 
as VDD it may not intialise the control program cleanly giving unpredictable 
results. I will look to see if the option boards use this rail.

When you have the problem check the voltages on 8T,8R and MUTE.

73
Stewart G3RXQ