[Elecraft] K2 trouble shooting

[Mike-WE0H]

Hi Don,

OK, on that line which is pin 14 on U3, there is only a couple mv but no 
pulses. The state of that line never changes. The other strange thing is 
the ENC-A data level only being 2v p-p verses ENC-B which is a full 5v 
p-p signal. Shouldn't both ENC data lines be a full 5v p-p TTL signal?

Worst case, does Elecraft take in repairs direct? I could send in both 
display boards if that is the case. I sure wish I had test boards to 
swap in, to verify which board is causing the issues.

I received the final amp rebuilding components the other day but I will 
wait to install them until after this dead VFO issue is repaired.

Mike
WE0H



Don Wilhelm wrote:
> Mike,
>
> Other than the wiring paths for ENC A and ENC B signals through the 
> connectors and to CB U6 pins 8 and 16,
> there is nothing else for these two signals.  However, for the encoder 
> to be read, the /ENC RD signal must be at a low level and that signal 
> is generated from FP U3 pin 14.  Look for low going pulses with your 
> scope.  If they are not present, FP U3 may be at fault.
>
> 73,
> Don W3FPR
>
>
> Mike-WE0H wrote:
>> Hi Don,
>>
>> Ref K2 #6698:
>>
>> I tried a new encoder but it did nothing different than the original 
>> encoder. Tonight I see that ENC-A is only 2v p-p while ENC-B is 5v 
>> p-p. This is measured right on the encoder terminals and on the U6 
>> MCU chip. I don't see any resistor network pull ups on these lines. 
>> Do you think the MCU could have gotten hurt with the spike on the 14v 
>> VCC line that shorted the one final and that VCC filter cap? I see 
>> data on both ENC lines when I spin the encoder. The Encoder VCC is a 
>> solid 5.0vdc. All other functions work on this radio except anything 
>> where I need to turn the encoder to access something in a menu or 
>> change anything. The radio receives fine on whatever the display freq 
>> is and transmits fine on the same freq on all bands. I just can't 
>> change any VFO digit other than the far right digit, or if I spin the 
>> encoder shaft left & right, it will slowly increase the displayed 
>> freq but not go down.
>>
>> Mike
>> WE0H