K1 Woes

[Rich Lim]

Hey guys, I'm helping a friend Al, W9AFR with his K1 and were have run into a problem. Here is the deal. We have built upto and including the RF board Part I with no problems. The first set of resistance checks checked out ok until we installed the electrolytic caps c33, c39, c35, c54, c31, c67, c9, c10 and c53, as well as U5 (voltage regulator) and jumper on RFC8.
 
Now when we do the DC voltage checks we have a short to ground on the power jack. We have double checked the polarity of the caps and they are correct. Furthermore re-doing the resistance checks on p29, we now get P1 pin 16 shorted to ground and U4 pin 7 at 10 ohm.
 
Would some "Elecraft Guru" out there give us some advice as where to look? I think that one of the caps is bad, but don't know which one to start replacing. I also wonder if D16 is bad too. If anyone can give us some advice, I'd sure appreciate it. Thanks alot guys!!
 
Rich
KQ9L
-------------------------------------------
K1 #1669, K2 #3232, KX1 #21
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[Jim Wiley-2]

Rich -

If you have a power short, there are various ways to fix it.  First,
look for solder bridges around components, IC's, etc.  If you don't find
any solder splashes or bridges, you may have a bad part.  Now, how do
you find it?  If the set was OK up until your last steps, then you only
have to look as the steps that were mad since the last "good" tests.


One very effective way I use is to use find shorts makes use of a
digital ohmmeter,  on it's lowest ohms range, set to display as many
digits as possible.  Hook one lead to the - (negative) power bus, and
search around with your meter, touching various + points (such as IC
power feeds or + leads of electrolytic caps)  until you see the lowest
ohms indication.  There will be very small differences as you move
around the circuit, and the closer you get to the short,  the lower the
ohms reading will be.  This probably won't work with an analog ohmmeter,
because you are looking for differences in the .001 Ohms area.  Here is
one area where a 5 or 6 digit meter really helps. I helped a friend find
a DC short in his QRP kit this way.


Good luck!


- Jim, KL7CC



Rich Lim wrote:

>Hey guys, I'm helping a friend Al, W9AFR with his K1 and were have run into a problem. Here is the deal. We have built upto and including the RF board Part I with no problems. The first set of resistance checks checked out ok until we installed the electrolytic caps c33, c39, c35, c54, c31, c67, c9, c10 and c53, as well as U5 (voltage regulator) and jumper on RFC8.
>
>Now when we do the DC voltage checks we have a short to ground on the power jack. We have double checked the polarity of the caps and they are correct. Furthermore re-doing the resistance checks on p29, we now get P1 pin 16 shorted to ground and U4 pin 7 at 10 ohm.
>
>Would some "Elecraft Guru" out there give us some advice as where to look? I think that one of the caps is bad, but don't know which one to start replacing. I also wonder if D16 is bad too. If anyone can give us some advice, I'd sure appreciate it. Thanks alot guys!!
>
>Rich
>KQ9L
>-------------------------------------------
>K1 #1669, K2 #3232, KX1 #21
>_______________________________________________
>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
>
>  
>

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