[Elecraft] K2 KSB2 help please

[Don Wilhelm]

The easiest way to check for a bad U1 (not likely unless it was damaged 
by static) is to replace it with one known to be working.
The other way is to make the DC measurements - use the chart near the 
end of the instructions.
See if the RXC, TXC, RXS, and TXS signals are being developed properly.
First make certain you have set the SSB FL1 filter to OP1.
During CW mode receive, you should have 5 to 6 volts on the RXC output 
(U1 pin 22) - changing the mode to either USB or LSB, the voltage at pin 
22 should drop to nearly zero and the voltage on RXS (U1 pin 21) should 
go up to 5 to 6 volts.
On CW transmit,  the TXC signal U1 pin 12) should go to 5 to 6 volts.  
Changing the mode to SSB and putting the K2 into transmit Close the dot 
side of the paddles) should bring TXS (U1 pin 15) to 5 to 6 volts.

If that is happening, U1 is working (although a static damaged output is 
still possible).  Check the soldering of U1 pin 28, both ends of R12, 
and P1 pin 2 carefully.  Also remove the K2 bottom cover and check the 
soldering of J11 pin 2.  Those points are on the AUXBUS signal line.  
Communication between the K2 MCU and KSB2 U1 is done over the AUXBUS, 
and for some reason they are not communicating.

73,
Don W3FPR

On 1/7/2013 3:45 PM, N8CEP wrote:
> I finished my KSB2 module and pluged it in. I get the normal "Elecraft" when
> powering up but I can not go further. I am getting "--" on the menu items
> SSBA and SSBC. I tried to do some voltage check and got 6 volts on U1 pin 1.
> I removed U1 and checked for bent or broken pins. I checked orientation of
> all diodes and electrolitics. I examined the board for solder bridges and
> reflowed solder on the parts that looked a bit bare. Now I am stuck. Is
> there any way I can check for a bad U1??
>
>