KX1: power on, no LED readout, then a burning smell

[John Shadle]

Oh no. I have no idea what I have done. I haven't used the KX1 for a
while (a couple weeks) and hooked it up to a 7Ah battery and switched on
the power. The battery was measuring 12.8v before I hooked up the radio.

As soon as I switched on the radio, I heard a little something in the
headphones (like a "pop", but not uncharacteristic of the KX1 turning
on), but no display on the LED.

I did smell something burning, though.

I powered off and took the case off (and smelled more burning odors).
When I took the board out of the enclosure and gave it the once over, I
found that the copper traces were exposed in the area between R16 and
R17 markings on the side with the crystals installed (see photo below).

http://www.flickr.com/photos/shadle/832402407/

I don't want to apply power again, but am not sure where to head next.

If anyone has any ideas, I would love to hear them. The traces that are
now exposed run from pin 10 of RP5 to U8 (not sure).

One thing I did notice, dealing with power, was that the internal
battery connectors were not connected to the board...but would that
matter if I wasn't even using internal batteries at the time?

Oh boy. I hope this is easy to fix or troubleshoot.

Thanks for your help, all.

-john W4PAH


_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

[John Shadle]

I love it when I answer my own questions. Thanks for the link to the
searchable archive at marc.info from a recent poster (N8VW), I found
this post from a few years back by W7SNH (Denny) by doing a search on
the keyword "burning". [Hahahahahaha.]

http://marc.info/?l=elecraft&m=111269643608699&w=2

It details exactly what happened to me. Time to install a fuse in my
power cord, first of all; then, I need to do some troubleshooting and
repairs to the board it appears. <sigh>

I learned my lesson!

-john W4PAH



_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

[John Shadle]

One more reply (to myself). I'm looking for some assistance now, I think.

I checked resistance on the tab of Q6 and get 1k ohm.
Resistance at pin 1 of U1 is 3.13k ohm.
Both are supposed to be over 500 ohm, according to p. 58 of the most
current manual.

D7 checks out at .742 one way and .538 the other way, so I think it's
alright (forgive my lack of technical jargon; I'm tired).

I think the only thing I may need to repair is the trace between RP5 and U8.

So, the question of the evening is...

Anyone have any idea why this happened? Was it just the fact that more
current was flowing through than necessary and my DC wasn't fused at 1A
or so? Everything else seems to be in order.

I just don't want worse damage next time, or to have to do this repair
more than once. Thanks for your help, all.

Off to bed!

-john W4PAH


_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

[Don Wilhelm-3]

John,

It would appear that your KX1 is OK except for the burned/vaporized
board trace.

One possible cause is a short from Q6 to the case when it is assembled.
  Check for burrs around the countersunk hole in the case and if you do
not have a nylon screw for securing Q6 to the case/heat-sink, you may
request one from Elecraft.

To repair the burned trace, scrape out all the burned part and clean the
solder-masking off the remaining ends of the trace.  Lay in a wire and
solder the ends.  If you want to make it 'pretty', use a bare wire
carefully dressed to fit the original path of the board trace and embed
it in a small amount of epoxy.  A green Sharpie marking pen can color
the epoxy and make the repair almost invisible.

73,
Don W3FPR

John Shadle wrote:

> One more reply (to myself). I'm looking for some assistance now, I think.
>
> I checked resistance on the tab of Q6 and get 1k ohm.
> Resistance at pin 1 of U1 is 3.13k ohm.
> Both are supposed to be over 500 ohm, according to p. 58 of the most
> current manual.
>
> D7 checks out at .742 one way and .538 the other way, so I think it's
> alright (forgive my lack of technical jargon; I'm tired).
>
> I think the only thing I may need to repair is the trace between RP5 and
> U8.
>
> So, the question of the evening is...
>
> Anyone have any idea why this happened? Was it just the fact that more
> current was flowing through than necessary and my DC wasn't fused at 1A
> or so? Everything else seems to be in order.
>
> I just don't want worse damage next time, or to have to do this repair
> more than once. Thanks for your help, all.
>
> Off to bed!
>
> -john W4PAH
>
>
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
> http://mailman.qth.net/mailman/listinfo/elecraft   
> Help: http://mailman.qth.net/subscribers.htm
> Elecraft web page: http://www.elecraft.com
>
>

_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

[Gil Stacy-2]

Don,
A little powdered Rit Dye dissolved in a few ml's  of rubbing alcohol will
dye epoxy. A drop or two of that mixture will color the small amount of
epoxy necessary to do the job.  An old flytying trick...
73, Gil NN4CW
_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com