[Elecraft] K2 #2456 is OFF THE AIR!

[Dan Barker]

Damn! And I really liked it.

I seem to have let the smoke out of my MCU, and I don't know how or why. =
Makes me think a new one will fail, too.

Support: Please send me U6 for the controller board. Warranty or bucks?

The Group: ANY IDEAS at all will be greatly appreciated (except "bend =
out pin 5 and slam it back in and go ahead on the air sans voltage =
readout").

History:

K2 #2456 went together fairly well. A bit of learning curve on the =
filters, and finally deciding  USB didn't really matter. LSB is fine. CW =
is extremely fine. I even use CW. Every checkpoint resistance, frequency =
and voltage were in spec on the first try. First QSO, 1/18/2002. Receive =
current, 0.22.

So, being lazy, I built the KAT2. Again, all FB right out of the box. =
Only 1 QSO tho, because the KIO2 kit was sitting on the bench. Played =
around with the relay music a bit, but it tuned up all bands on my low, =
40m dipole (well, 3.3:1 on 80m - but that's to be expected). Only QSO, =
1/24/2002. Receive current, 0.23.

On to the KIO2. I wondered about having to cut a land on the control =
board, but the silk-screen clearly stated Revision A, and there was a =
land from Controller board U6/25 to Q5's gate. I'd have thought a 2-week =
old kit would have the latest and greatest boards. The screening says =
1999, tho. Could just be the art.=20

I really don't think I moxied up the board, but it's very hard to see. =
Every nearby land I can check appears fine. However, it powers up with a =
"Low Battery" warning, and pulls 0.34 amp receive. Receiver works fine, =
transmitter works fine, tuner tunes fine, but the Voltage display is =
0.08. Oh yes, the KIO2 doesn't work either. I didn't get into that too =
deeply, because I had that high current to worry about. I'll look over =
the KIO2 with a fine tooth magnifying glass while I scratch my head and =
wait for a chip.

Being concerned about the "mystery" 0.1 amp (that's a lot when you don't =
know where it's going), I inspected the poo out of everything. There =
just is not a [visible] short on the board. Maybe a clipping got under =
something, but I can't figure out where. The inspection shows R8 =
discolored (meter still shows 98.5, so I'll leave it until it fails), =
and U3 somewhat warm.

12v on S1. 12v on U3 pin 5. 0v on U3 6&7. Ov on U6 pin 5. Oh No!

Powered off, U6 pin 5 (V SENSE) shows 2.4 ohms to ground. I know it's =
probably U3 or something on the board, but I pulled U6 anyhow, since =
it's socketed. Now pin 5 (of the socket) shows it's expected 10 Megohms =
(yeah right) to ground. The chip, sitting on the bench in it's foam, =
shows 2.4 ohms from pin 5 to 31 (either polarity on the probed). That =
ain't right!

Can someone give me resistance to ground on all 40 pins of the socket =
with U6 removed (Rev A, land cut, 2 jumpers and a cap)? It's likely not =
that, but I gotta check before putting in another MCU.=20

Very sad WG4S, I guess the Cubic Astro-103 has a few more QSO's in it, =
but I'm really gonna hate twisting all those big knobs on the old =
Griefkit tuner. Gotta put 1/4 inch jacks back on everything too :-(