[Elecraft] K2 Encoder problems continue.

[Nidge (Nigel Smith)]

Hi Don and Geoff

Thanks for the replies both.

First of all Geoff: I'm afraid I don't have a scope here anymore.  I did
remove the MCU
and checked the voltages, and this time on pin 14 of U3 I had the correct
voltage close
to 3.8V, with the MCU inserted it was below 100mV.

Don:  I've checked the the readings at TP1, when spinning the encoder the
frequency
does not change.  At TP3 the frequency is close to 12,100KHz with Band +
and close to 12,085KHz with Band - .

I've also checked the 4MHz oscillator and this is spot on.

The radio, when connected to Hamradio Deluxe works fine under computer
control, both
on receive and transmit.  The filters are off but that's because I'm unable
to fine tune them
as the encoder isn't working.

Any more thoughts on the matter greatfully received.

Regards

Nidge (G0NIG)

IO93dv

----- Original Message ----- 
From: "Don Wilhelm" <w3fpr at embarqmail.com>
To: "Nidge (Nigel Smith)" <nig_smith at o2.co.uk>
Cc: <Elecraft at mailman.qth.net>
Sent: Saturday, April 17, 2010 10:27 PM
Subject: Re: [Elecraft] K2 Encoder problems continue.


> Nidge,
>
> Is it that the last digit changes, but the K2 actually changes frequency
> (that would be a display problem) - OR - does the K2 frequency not move
> properly?
>
> Set the K2 to 40 meters.  Put the internal counter probe into TP1 and
> set the menu for CAL FCTR.  Try moving the K2 VFO dial - does the
> frequency move with the dial movement (it normally does).
> Now put the counter probe in TP3.  Tap the BAND+ button and note the
> frequency - it should be near 12,100  kHz.
> Now tap the BAND- button and again note the frequency - it should now be
> near 12,085 or so, and it should stay there.
>
> If it fails any of those tests, you have a problem with the DC voltage
> being applied to the PLL Reference Oscillator.  I can give you some
> additional points to check if that appears to be the problem.
>
> 73,
> Don W3FPR
>
> Nidge (Nigel Smith) wrote:
>> Turning the dial only results in the last digit displayed flicking 
>> backward and forward.
>> Initially it was thought that the encoder was at fault and a replacement 
>> was ordered.  Unfortunately
>> once the replacement was installed the problem persisted.  It was 
>> suggested by a Don (W3FPR)
>> that because the voltage on pin 14 of U3 to the encoder enable pin was 
>> low
>> (only 100mV or less) that the output of this drain was faulty.  Replacing 
>> the TPIC6B595N
>> did not rectify the problem.
>>
>> I have checked continuity between the ENC-A/B outputs of the Encoder 
>> through the
>> display board and back to the MCU and all checks out OK, as does the 
>> 5Volt supply.
>>
>> The remainder of the front panel functions work as they should.
>>
>> I must admit I am completely stuck now as to what else could cause this 
>> problem,
>> especially as the radio has not missed a beat since it was constructed.
>>
>> Any pointers that any of you might have would be very much appreciated.
>>
>> Regards
>>
>> Nidge (G0NIG)
>>
>> IO93dv
>>
>>
>> A wise man speaks because he has something to say; a fool because he has 
>> to say something
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