Re: Check Your Buttons [switch current is _not_ too low]

[wayne burdick]

David G3UNA, wrote:
> A quick look at the circuit diagram shows that buttons are taken  
> from a
> potential divider to CD74HC4051M inputs.  These switches (unless I've
> misread the diagram) will therefore take the input current of the
> multiplexer which is typically <1uA.  I don't know the spec for the  
> Elecraft
> switch but a similar one requires a minimum current of 10uA.  This  
> should be
> checked more rigorously, but it might indicate a potential problem.
David,

The K3's front panel switches do not have a minimum required current.  
I just verified this again with the manufacturer. They have gold-
plated contacts on the PC board and should be extremely reliable.

Regarding the switch test function in the menu: A small amount of  
digit flicker is perfectly normal. The A to D converter has an  
ambiguity of +/- one count, and the firmware algorithm reading the  
switch has no hysteresis, therefore +/- count of flicker is also to be  
expected.

In firmware, we read the switch voltage several times, average them,  
and look for the proper switch code based on "bins" that have a large  
amount of excess margin. So the operator should not be concerned in  
the least about a deviation of even several counts in their own switch  
read voltages.

If you're experiencing any type of switch-read error that isn't a hard  
failure, it is probably something that I can improve in firmware. I'll  
be happy to work with you on this -- please give me a detailed example.

73,
Wayne
N6KR

 
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[AD6XY]

I remember having this problem with an old Advantest Drift-o-matic spectrum analyser at Uni. The buttons stopped working because the plastic let out some oils and this coated the gold and stopped the contacts working. I am not saying this is what has happened to Elecraft, I am sure that problem from 20 years ago if fixed now. My fairly recent Anritsu spectrum analyser has diffficult buttons too - as apparently does this laptop so it is a common problem.

My K3 has sometimes had problems with switches too, but only rarely. My K2 is much worse in this respect.

Have we found any user applications for the connector on the bottom of the panel yet?

[.hank.]

AD6XY wrote

My K3 has sometimes had problems with switches too, but only rarely. My K2 is much worse in this respect.

Have we found any user applications for the connector on the bottom of the panel yet?

At least on the K2 with it's bouncing switches it is not only a known problem, especially with the A/B and A=B switches, but you can fairly easily replace them - I changes out about 20 of them on my two K2s.  And you get some physical feedback on the K2.  On the K3 that is not true.

[Mike S-8]

At 06:54 PM 9/24/2009, .k8dd. wrote...
>At least on the K2 with it's bouncing switches it is not only a known
>problem, especially with the A/B and A=B switches, but you can fairly
>easily
>replace them - I changes out about 20 of them on my two K2s.

K2 switches are readily available from Mouser and Digikey (Elecraft,
too, obviously). E-switch TL1100F160Q. I mention this because it's an
easy thing to add on to an order, and it's handy to keep some spares.

A couple of other common parts:
Potentiometers, 9mm snap in - Alpha 9mm (mouser 317-2080F-5K,
317-2090F-5K)
Headphone jack - Kobiconn 161-3503-EX


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