[Elecraft] Smoke back in L1?

[Jeff Burns]

I managed to let the smoke out of the L1 on the AUX2 board. I was making up
a combination of cables and adapters to connect my HP48 calculator to the
KIO2. I had it all working with some crossover jumpers until I added the
last gender changer. It turns out that even though the interface cable only
has 4 wires on the calculator end it connects all the unused pins to ground.
It worked great until I replaced my jumpers with an adapter that connected
all the pins. I connected pins 1, 4, 6, 7, 8, and 9 of the AUX2 together.

I have verified that L1 on the AUX2 was open. Putting a jumper across L1
made it possible to reestablish communications with the K2.

Now I have three questions:

1. Are there other parts that may have been damaged by this mistake that may
not be immediately obvious? If so what should I check for?

2. In WA7GXD's instructions for remote mounting the KPA100
http://www.fidalgo.net/~wa7gxd/k2kpa100.html he describes upgrading L1 using
a toroidal inductor. I am wondering what the critical parameters for this
part are, and if I can use one of the two toroids I have in my junk box.

The first part I have is the old L33 that I removed for the BFO upgrade.
Second I have a bunch of Ferrite beads I purchased from the WireMan to make
a choke balun for a 2m antenna. I am not sure what these are. My best guess
after looking at the WireMan web page is that they are FB 43-2401 u=850.
They are 0.35 inches in diameter if that helps anyone identify them.

Can I use either of these parts to make a new L1?

3. If the current rating of L1 is upgraded what will fail if I make a
similar mistake again? Should a fuse be added someplace?


By the way I am close to getting the K2 interfaced to the HP48.  I will
share the results as soon as I have it completed.


Jeff Burns
AD9T