K2 Audio Loss Due to ESD

[Roy Morris-6]

I have come up with what I think is a better mod for grounding the mike connector (J2) on the Front Panel board.  The two standoffs were removed on each side of the mike connector.  The two lockwashers on each standoff were removed.  Two small expansion springs (about 1/2" X 3/16" before expansion with the last loop on each side lying flat to accept screw) were purchased at the hardware store.  I placed the two springs on one screw securing them with the standoff, routed them on each side of J2, and joined them on the other standoff.  These standoffs are at ground potential.  I did not replace the two lockwashers on each standoff.  This mod seems to make a good ground.  Hopefully, this along with good grounding and well sanded panel connections will help eliminate loss of audio due to ESD zaps to K2/100s with the KDSP2 installed.  Roy Morris  W4WFB
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[Jim Brown-10]

On Wed, 13 Apr 2005 16:56:50 -0400, Roy Morris wrote:

>I have come up with what I think is a better mod for grounding
>the mike connector

The ONLY good place to connect the shield of the mic cable is to
the chassis of the K2. I have modified one of my K2's to do this,
and will do the other one (newly acquired) soon. When you connect
the shield to the circuit board and from there go to the chassis,
you set up what we in the pro audio world know as a "pin 1
problem."

You can find a tutorial on this as part of AES48, an international
standard that I helped write. At www.aes.org, go to Standards,
then Standards in print, and then select AES48. Anyone can
download a pdf of the standard at no charge. If you are not an AES
(Audio Engineering Society) member, you won't be able to print the
pdf, but you can read it on your screen. You can buy a printable
copy for $25.

BTW, the chassis is also the "right" place to connect the signal
return of RS232 connections, NOT pin 5. I've solved some serious
RFI problems by correcting this.

This is a tutorial on the topic.

http://audiosystemsgroup.com/FerritesRFI-HamPPT.pdf 

There are other tutorials on the website that you may find
helpful.

http://audiosystemsgroup.com/publish.htm

Jim Brown  K9YC


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