[Elecraft] K2 Keypad

Sat Aug 10 22:55:19 EDT 2024

Bill- You'll be very happy with the work Dave does on your K2- he had mine in for repair in late 2022 and it came back to me working like a champ!
Mine was also acquired in a private sale in August 2022; I didn't build it. (I'm the 3rd owner I believe- it is serial #663, so it's an early rig.)
There were several upgrades done to the rig by the previous owners that were only partially completed, and Dave repaired and upgraded mine to the current standard, topped off with an alignment.
He kept me well posted during the K2's repair journey, and we had several memorable conversations along the way.
The result was superb, and I was very pleased with his work- I believe you will be too.
Have a good weekend!

73

v/r, Chris "Doc" Rhoney/W4VHZ sends...
________________________________
From: elecraft-bounces at mailman.qth.net <elecraft-bounces at mailman.qth.net> on behalf of William Santos via Elecraft <elecraft at mailman.qth.net>
Sent: Saturday, August 10, 2024 1:01 PM
To: Dave W8FGU <dave at w8fgu.com>
Cc: Elecraft Reflector <elecraft at mailman.qth.net>; Michael Carter <Mike.Carter at unh.edu>
Subject: Re: [Elecraft] K2 Keypad

Dave, Don, and Mike,

Thank you so much for your help. You zeroed right in on the problem with my K2.

As I said earlier, I didn't build this radio, but recently acquired it in a private purchase. I do have a K2 kit I got directly from Elecraft a few months ago, and am eagerly looking forward to digging in to building one myself. Though I've successfully built a number of projects, I'm not ready to attempt repairing the K2 in question till I've familiarized myself with the design and have built one myself from scratch.

So I would like to submit the K2 we've been talking about to Dave for repair of the U3 chip and any other necessary fixes or alignments.

Dave, I'll email you privately to make arrangements for shipping it to you.

Again, you guys are the best! I really appreciate and am honored to have your help!

Take care and 73,

Bill
KN6UDK

> On Aug 7, 2024, at 3:56 PM, Dave W8FGU <dave at w8fgu.com> wrote:
>
> Ok Bill, that pin might be bad. Those chips are highly suseptible to static discharge.  I'm thinking you may have to replace U3. Or if you can safely remove U3, then measure it again and see if something else is pulling it up.
>
> 73,
> Dave, W8FGU
> Aug 7, 2024 18:35:16 William Santos <santos at mac.com>:
>
> OK, pin 16 on U3 reads 4.967V, (essentially 5V) so it appears it's staying at 5V and not being pulled down.
>
> Inspecting the solder on pin 16, it doesn't look like a cold joint.
>
>> On Aug 7, 2024, at 11:46 AM, William Santos <santos at mac.com> wrote:
>>
>> Thanks Dave,
>>
>> I will open the 2 up and test with the multimeter when I get home from work. I'll report back with the voltage I see.
>>
>> I do have a scope, but haven't used it much and never hooked it up to a radio this complex before.
>>
>>> On Aug 7, 2024, at 11:43 AM, Dave Van Wallaghen <dave at w8fgu.com> wrote:
>>>
>>> Bill,
>>>
>>> Don and Mike have you looking in the proper location on the Front Panel Board. I suspect that the RIT/XIT pot does not work as well, but as you say, you can't invoke RIT or XIT at this time to determine this. Something is not allowing the /BANK2 signal to occur in order to scan those controls on the right side. FP U3 P16 is where that signal originates. Maybe a cold solder joint on U3 P16 or something shorting the /BANK2 path to a high voltage.
>>>
>>> If you have a scope, you could look at U3 P13 and see it being pulled down in around 5us pulses as I am measuring here. If not, then you might try using a DMM to measure that pin. I am seeing around 4.6v and it fluctuates. If it is at the high 5v level, then it is not being pulled down by U3. Again, either something keeping that line high or bad pin 13 on U3.
>>>
>>> 73,
>>> Dave, W8FGU
>>>
>>>
>>>
>>> On 8/7/2024 11:45:30 AM, "William Santos via Elecraft" <elecraft at mailman.qth.net <mailto:elecraft at mailman.qth.net>> wrote:
>>>
>>>> Hi Mike,
>>>>
>>>> Thanks for your response and attention to my issue.
>>>>
>>>> Yes, it is only the buttons to the right of the LCD that are affected.
>>>>
>>>> All of the pots to the left of the VFO knob work properly, as do all the push buttons on the left (BAND+ through NB). To the right of the LCD, I can only confirm the MODE(1) and ON/OFF buttons work. Buttons A/B(2) through MSG(9) do not elicit a response. Unable to test the -1 0 +1 potentiometer, as I think all of it's functions require actuating one of the buttons on the keypad.
>>>>
>>>> To summarize, buttons 2 through 9 on the keypad are nonfunctional, and everything else seems to work.
>>>>
>>>> Thanks and 73,
>>>> Bill
>>>> KN6UDK
>>>>
>>>>> On Aug 7, 2024, at 8:23 AM, Michael Carter via Elecraft <elecraft at mailman.qth.net <mailto:elecraft at mailman.qth.net>> wrote:
>>>>>
>>>>> Hi again, Bill,
>>>>>
>>>>> I re-read your post and realized that
>>>>> it's only the buttons to the right side
>>>>> of the LCD display that fail to function
>>>>> (with the exception of the MODE button).
>>>>> Is that correct?
>>>>>
>>>>> If so, I will retract my statement about
>>>>> the parallel load shift register not working
>>>>> properly. If it works for the buttons to the
>>>>> left of the LCD display, then the shift
>>>>> register is working OK. It would then
>>>>> seem that the BANK2 switches to the
>>>>> right of the display are not being polled.
>>>>> The /BANK2 signal that polls these
>>>>> switches is generated in U3, a 6B595
>>>>> shift register. That shift register
>>>>> receives data serially from the MCU
>>>>> and produces the /BANK1 and /BANK2
>>>>> signals that activate each switch
>>>>> bank in turn. U3 also generates the
>>>>> /ENC_RD signal that allows the
>>>>> main tuning knob to be read.
>>>>>
>>>>> Please confirm which controls do
>>>>> register any response, including
>>>>> the 4 potentiometers to the
>>>>> left of tuning knob.
>>>>>
>>>>> Thanks, and 73,
>>>>> Mike, K8CN
>>>>> ______________________________________________________________
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