Re: K2 VFO Freq Display Stuck (again)

Posted by Don Wilhelm-4 on Jun 17, 2012; 11:31pm
URL: http://elecraft.85.s1.nabble.com/K2-VFO-Freq-Display-Stuck-again-tp7136782p7557749.html

Casey,

Yes, you did the measurements correctly, but there is some confusion in
my mind about the EncRD signal.  Certainly with no load connected the
voltage on U3 pin 14 should be 3.3 volts or higher.  So U3 must be
replaced for certain.

Just as clarification, 0.4 volts is equal to zero in the digital realm
and 0.46 is equal to 5 volts nominal - the data is "binary", so it is
either ON or OFF - in other words, less than 1 or 2 volts and greater
than 3.5 volts for TTL levels.

One more check on the encoder - see if leads 3 and 4 switch voltages
together - if they do, there is something shorted in the encoder and it
must be replaced.  If they are independent, replace only U3 and test again.

Sorry for the lack of a definite answer, and I understand that VK-land
is not a 2 to 3 day parts request to delivery time, but based on the
info I have, that is the best answer I could muster.

73,
Don W3FPR


On 6/17/2012 7:17 PM, TI2/NA7U wrote:

> Yes, I remember that Enc B was fine last time, also, but it's definitely not
> now.
>
> One correction to my previous post, when the encoder is connected the
> voltage on Enc B and Enc RD vary between .4-.46V, not from zero.
>
> With the encoder pins 3 and 4 disconnected and measuring directly at the
> encoder pins I see the voltage hold about 4.4V on both 3 and 4. As I turn
> the encoder the voltages on either pin drop to zero, but only
> intermittently.
>
> The voltage at U3 pin 14 is about .3V (even when the encoder pins are
> connected it measures about .1V, whereas the voltage chart says it should be
> 3.1V and varying).
>
> Hope I did the measurements correctly.
>
> 73,
>
> Casey
>
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