[Elecraft] Re: Help, I think I've killed my K1

[John Webster]

Greetings:  [Rather Lengthy]

This is a long-overdue final report on a thread started back 
in February.  While the problem was solved by mid March,
I have been away so much that I have not had a chance to 
wrap this up properly, and thank those who helped.  

The symptom was sudden relay chatter, LED flashing and
then silence from my K1, while tuning a manual antenna 
matching device (a K.W. Electronics E-Zee Match), and 
keying my 100 watt base station rig (Kenwood TS-850).

The initial problem turned out to be a blown Front Panel
Board 6v regulator, due to high RF field from the tuner 
while the K1 was on standby (but antenna disconnected).  
The damage seems to have been caused by induced high 
voltage/current.  The K1 was too close to the antenna 
tuner (only some 3 inches away from it), and was thus 
affected by the very high energy fields that can be 
generated by large air core inductors with high SWR on 
the feedline.

It took a little work to find and solve the damage to the K1.
The members of the list proved invaluable.  Particular thanks
are due to:  Mike KK5F; Bob AG5Q; Stuart K5KVH; 
Trevor KG6CYN; and Jessie Oberreuter.

It was quickly determined that the 6v regulator on the Front
Panel Board was blown.  None of the other voltage regulators
were faulty, and the problem was thus isolated to the FP 
board.  Replacement (with a locally obtained 6.2 volt reg.,
NTE-988) brought the K1 to life, but not to full health.  I 
suspected the NTE-988 and ordered the correct ZR78L06C 
from Elecraft.  But much to my chagrin, this did not solve the 
anomalies.  Upon checking, the voltage output was being 
pulled down to 4.3 volts (only 232 ohms to ground).

Now the search got serious.  With help from Mike and Bob, 
I proceeded to isolate the output of the regulator from 
everything else connected to it (even C4 & C5).  As 
Murphy's Law would have it, the last part I checked was 
U2 the D/A Converter (MAX518).  On lifting U2 pin 7 
the low resistance to ground disappeared.  But the output
of the 6volt regulator was still too low (5.25 volts).  Some-
thing was still wrong!  Again, with help from Mike, it turned
out that the regulator was not happy with C4 and C5 lifted.
 
Finally, with a replaced D/A Converter from Elecraft ($10),
and everything else reconnected, the K1 has once again
worked flawlessly every since.

Lessons learned:

1. This list is an incredibly valuable resource.  The combined
talent, skill, experience and know-how on here is priceless.

2. I gained enough confidence to fix a non-trivial problem on
my K1, and learnt a whole lot about the circuit in the process.

3. To remove an IC, cut its pins, and then desolder them carefully.  
To isolate a trace, you can cut a single pin and lift it up, and then 
resolder it back, without leaving hardly even a trace.

4. I need a Hakko 808 desoldering tool!

5. Don't put your K1 (or K2?) near Antenna Tuners (particularly
those with air cores).  It turns out that almost the identical problem 
has happened to two others before (Jessie and Trevor).  Beware.
[I take it that the toroid cores of the ATU's in the K1, K2 and in
the KAT100 are less of a problem].

6.  Be careful with the K1 when you have it switched to "S-meter"
(reading relative signal strength).  With no signal present, and the 
volume turned down, you have no way of knowing whether the rig 
is on or off.  I always turn the display back to "normal" if I leave
the rig on, while unattended.  [Doesn't help in the dark, of course!]

7. I'm so impressed with the K1 that I have bought a K2 to build
. . . now to find the time!

Thanks for reading this long winded and long overdue post.

73

John, N6JW