K2 KSB2 help please

[N8CEP]

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??

[N8CEP]

Checked everything very carefully. Still no menu SSBA or SSBC.

[Don Wilhelm-4]

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??
>
>

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[N8CEP]

OK Don - here is what I found.

First I checked pin 2 on the KSB2. It was ok and I checked continuity from pin 2 to R12 and from R12 to U1 Pin 28. All checked out OK. I then checked the soldering of J11 pin 2. I touched it up and double checked for solder bridges.

KSB2 was reinstalled and it showed 5.56 volts on pin 28.

I setup SSB filter F1 for OPT1 on CW and USB and LSB.

I show 0 volts on pin 22 in receive USB or LSB.
I show 0 volts on pin 21 in receive USB or LSB.
On CW transmit I show 0 volts on TXC signal U1 pin 12.
On SSB transmit I show 0 volts on TXS signal U1 pin 15.

Thanks!  Keith N8CEP

[N8CEP]

Don - thanks for your help. My new Microcontroller U1 and new ceramic resonator Z1 arrived in the mail this afternoon. Installed them tonight and everything works! Must remember to be more careful with static precautions in the future!

73
Keith N8CEP

[Don Wilhelm-4]

Keith,

That is good news.  Enjoy.

73,
Don W3FPR

On 1/11/2013 7:34 PM, N8CEP wrote:
> Don - thanks for your help. My new Microcontroller U1 and new ceramic
> resonator Z1 arrived in the mail this afternoon. Installed them tonight and
> everything works! Must remember to be more careful with static precautions
> in the future!
>
>

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