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K2 VFO / Encoder Problem

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Nidge_(G0NIG)

K2 VFO / Encoder Problem

I have in my possession a K2 that has developed a fault with
the encoder.

When trying to tune the radio, rotating the encoder results in just
the last digit displayed flickering back and forth.

At first I thought the Optical encoder had failed and so ordered a
replacement from Elecraft which arrived yesterday. Today I installed
the new Encoder only to find that the problem still persists.

I have checked and confirmed there is a 5Volt supply on pin1 of the
encoder, pins 2 and 3 fluctuate between 5Volt and 0.1Volt when the
encoder is advanced or retarded. Pin 4 appears to remain at 0.1Volt.
In the voltage charts at the back of the manual Pin 4 is connected to
pin 14 of U3, this according to the charts should be about 3.1Volt.

Obviously the encoder is not at fault, unless I've been un-lucky
enough to have received another duff one.

Any advise on where I should be looking now. Could it be possible
that U3 has failed as some of the pin voltages for this IC do
not correspond to those listed at the back of the manual.

Many Thanks in Advance.

Nidge (G0NIG)

IO93dv
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Don Wilhelm-4

Re: K2 VFO / Encoder Problem

Nidge,

It is difficult to predice the exact voltage levels that will be present
in digital signals at any particular time. That may be why the U3
redings may be off from what is listed in the manual. Check by
comparison instead.
Compare the voltage at FP U3 pin 14 with the voltage your meter reads at
pins 7 and 15 - they should be similar. If they are not, then it is
likely that U3 has a damaged output at pin 14.

Additionally, check to be certain the signal at encoder pin 2 is making
it to CB U6 pin 8 and the signal at encoder pin 3 makes it to CB U6 pin 16

73,
Don W3FPR

Nigel (Nidge) Smith wrote:

> I have in my possession a K2 that has developed a fault with
> the encoder.
>
> When trying to tune the radio, rotating the encoder results in just
> the last digit displayed flickering back and forth.
>
> At first I thought the Optical encoder had failed and so ordered a
> replacement from Elecraft which arrived yesterday. Today I installed
> the new Encoder only to find that the problem still persists.
>
> I have checked and confirmed there is a 5Volt supply on pin1 of the
> encoder, pins 2 and 3 fluctuate between 5Volt and 0.1Volt when the
> encoder is advanced or retarded. Pin 4 appears to remain at 0.1Volt.
> In the voltage charts at the back of the manual Pin 4 is connected to
> pin 14 of U3, this according to the charts should be about 3.1Volt.
>
>

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Nidge_(G0NIG)

Re: K2 VFO / Encoder Problem

Hi Don,

Many thanks for the quick reply.

So far the readings I get on U3 are as
follows:

Pin 14 = 0.1V and 0.133V when the encoder is
rotated.
Pin 15 = 4.12, which varies when the encoder is
rotated.
Pin 7 = 3.4V with slight variation when the
encoder is rotated.

So from the above would you say it's safe to
assume that U3 has a damaged output on
pin 14?

Again thanks very much for taking the time
to reply.

Regards

Nidge (G0NIG)

IO93dv

----- Original Message -----
From: "Don Wilhelm" <[hidden email]>
To: "Nigel (Nidge) Smith" <[hidden email]>
Cc: <[hidden email]>
Sent: Thursday, April 08, 2010 9:17 PM
Subject: Re: [Elecraft] K2 VFO / Encoder Problem

> Nidge,
>
> It is difficult to predice the exact voltage levels that will be present
> in digital signals at any particular time. That may be why the U3
> redings may be off from what is listed in the manual. Check by
> comparison instead.
> Compare the voltage at FP U3 pin 14 with the voltage your meter reads at
> pins 7 and 15 - they should be similar. If they are not, then it is
> likely that U3 has a damaged output at pin 14.
>
> Additionally, check to be certain the signal at encoder pin 2 is making
> it to CB U6 pin 8 and the signal at encoder pin 3 makes it to CB U6 pin 16
>
> 73,
> Don W3FPR
>
> Nigel (Nidge) Smith wrote:
>> I have in my possession a K2 that has developed a fault with
>> the encoder.
>>
>> When trying to tune the radio, rotating the encoder results in just
>> the last digit displayed flickering back and forth.
>>
>> At first I thought the Optical encoder had failed and so ordered a
>> replacement from Elecraft which arrived yesterday. Today I installed
>> the new Encoder only to find that the problem still persists.
>>
>> I have checked and confirmed there is a 5Volt supply on pin1 of the
>> encoder, pins 2 and 3 fluctuate between 5Volt and 0.1Volt when the
>> encoder is advanced or retarded. Pin 4 appears to remain at 0.1Volt.
>> In the voltage charts at the back of the manual Pin 4 is connected to
>> pin 14 of U3, this according to the charts should be about 3.1Volt.
>>
>>

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Don Wilhelm-4

Re: K2 VFO / Encoder Problem

Nidge,

Yes, from that I would surmise that U3 pin 14 is damaged - however,
check the ENC A and ENC B lines for continuity to the microprocessor
just to be sure there is nothing wrong there.

73,
Don W3FPR

Nigel (Nidge) Smith wrote:

> Hi Don,
>
> Many thanks for the quick reply.
>
> So far the readings I get on U3 are as
> follows:
>
> Pin 14 = 0.1V and 0.133V when the encoder is
> rotated.
> Pin 15 = 4.12, which varies when the encoder is
> rotated.
> Pin 7 = 3.4V with slight variation when the
> encoder is rotated.
>
> So from the above would you say it's safe to
> assume that U3 has a damaged output on
> pin 14?
>
> Again thanks very much for taking the time
> to reply.
>
> Regards
>
> Nidge (G0NIG)
>
>

Nidge_(G0NIG)

Re: K2 VFO / Encoder Problem

Thanks Don and Gary.

Have checked for bad joints and none found.

I've also checked for continuity between the
EncA and B to the main processor and they
are good.

The radio wasn't built by me but it had another fault
which I sorted. Unfortunately during the first repair
process I dislodged a screw that had been dropped
between the displayboard and control board by a
previous user and I think that's what more than likely
has taken out U3.

I may have a replacement in my spares box somewhere
if not it will have to be ordered.

Now getting very late here and I have a 5am start so
will search later tomorrow.

Many thanks to you both for replying.

Regards

Nidge (G0NIG)

IO93dv
----- Original Message -----
From: "Don Wilhelm" <[hidden email]>
To: "Nigel (Nidge) Smith" <[hidden email]>
Cc: <[hidden email]>; <[hidden email]>
Sent: Thursday, April 08, 2010 9:52 PM
Subject: Re: [Elecraft] K2 VFO / Encoder Problem

> Nidge,
>
> Yes, from that I would surmise that U3 pin 14 is damaged - however,
> check the ENC A and ENC B lines for continuity to the microprocessor
> just to be sure there is nothing wrong there.
>
> 73,
> Don W3FPR
>
> Nigel (Nidge) Smith wrote:
>> Hi Don,
>>
>> Many thanks for the quick reply.
>>
>> So far the readings I get on U3 are as
>> follows:
>>
>> Pin 14 = 0.1V and 0.133V when the encoder is
>> rotated.
>> Pin 15 = 4.12, which varies when the encoder is
>> rotated.
>> Pin 7 = 3.4V with slight variation when the
>> encoder is rotated.
>>
>> So from the above would you say it's safe to
>> assume that U3 has a damaged output on
>> pin 14?
>>
>> Again thanks very much for taking the time
>> to reply.
>>
>> Regards
>>
>> Nidge (G0NIG)
>>
>>