[Elecraft] [KX1] - Display dead after 30m/80m install

[Don Wilhelm]

Dave,

It sounds like U1 is not plugged in securely.  When U1 is inserted into 
the socket, most of the narrow part of the IC pins are fully into the 
socket.  It does take a bit of pressure to seat U1 in the machine pin 
socket.  Make certain all the pins are started into the socket pins and 
then apply pressure with both thumbs on the IC body, fingers under the 
board and squeeze until the leads seat completely.

If that does not cure the problems, look critically at the soldering.  
The solder should flow out to an almost invisible edge on both the 
solder pad and the component lead at each connection.  If there is a 
defined edge to the solder, insufficient heat was applied during the 
soldering process.  I am not certain why, but from the number of KX1 
repairs that I have done, soldering problems are more common with the 
KX1 than other Elecraft kits.  Perhaps builders are more hesitant to 
apply sufficient heat due to the more dense component placement, but 
somehow that does happen.  If the solder connections look more like ' 
balls' than 'mountains' having a concave fillet, you can be certain 
insufficient heat was used during the soldering process, and the only 
cure is to wick away the excess solder and apply good solder using 
sufficient heat (700 to 750 deg F).

73,
Don W3FPR

David Wilburn wrote:
> I'm helping a friend troubleshoot a KX1.  Unit was fine after build. 
> Took unit apart and installed 30m/80m.  Then 3rd digit did not work on 
> display.  He re-flowed some pins on the unit (I do not know which ones 
> and he does not recall) and now the display is not functional at all.
>
> I started him checking through the resistance checks on page 26 of the 
>   document.  Pins 1 & 20 of U1 has about 500 ohm on it, whether U1 is 
> installed or not.
>
> We have been all through the voltages with D3/D2, U8, and U9.  All the 
>   regulators seem good.  Though I did caution him about running from a 
> wall wart.  His 12v seems a bit low.  Around 11.5v.
>
> As a result of this, the voltage on pin 4 of U1 is a bit low at 3.5v. 
>   Also pin 14 is at 2.5v where it is supposed to be low.
>
> I find little odds and ends here that are not right, but if the 
> display is not functional I would expect bigger issues.  Some voltage 
> off on clock inputs wouldn't seem the culprit.  Also the ATU was not 
> plugged in.
>
> We have worked through the troubleshooting tree, problem 00,  I need 
> to review with him where he is on problem 20.  We looked through 
> problem 26.  No pins are bent on U1.  All of the voltages were good 
> except the 2 mentioned.
>
> I have not built a KX1, but built a K2.  My thoughts are to go through 
> the various resistance and voltage checks for the 3 build sections and 
> see if we can make any sense of it.
>
> Am I headed in the right direction?  Am I missing anything obvious 
> since I am not familiar with the KX1?
>
> I'm hoping my friend (John, K6OWD) got setup on the list today.
>
> Dave Wilburn
> NM4M
> K2/100 S/N 5982
> K3/100 S/N 766
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